Biochemistry Key Answers

Paper IV April 2001 Sub code: 4003

I) 1. Arrangements of tracts in internal capsule:

- Internal capsule is a mass of white fibers lying between the basal ganglia and thalamus. - Laterally by lenticular nucleus - Medically by caudate nucleus and thalamus.

Pyramidal tract in internal capsule:

- in horizontal section the internal capsule is ‗V‘ looking medical (a) the pyramidal tracts lie in the Genu, and anterior 2/ 3rd of posterior limb (b) other tracts present in the internal capsule are a. corticonuclear b. frontopontine c. lateral fifth of the temperopontine fibers

(c) Posterior limb of internal capsule where superior colliculi is present contains the tract of optic and olfactory pathway.

2. a) Cyanosis:

Cyanosis is defined as bluish discolouration of skin and mucous membrane due to increased amount of reduced haemoglobin above 5 mg / dl.

Types of cyanosis: (a) Central cyanosis:

a. Respiratory causes i. Decreased oxygenation ii. Impaired diffusion across resp membrane Eg. COPD b. Cardio vascular causes i. A-V admixture ii. Congenital anomalies Eg. ASD, Tetrology of fallot etc.

(b) Peripheral cycnosis: a. Stagnant hypoxia b. Obstruction to vessels at peripheries c. Fracture

Sites: ear lobes, fingers etc.

b) Near response :

- Also called accomadation reflex - It is a three part response when n individual looks at a near object o Contraction of ciliary muscles o Contraction of pupil o Convergence of visual axis

Accomadation pathway:

Retina

Optic nerve (visual pathway)

Primary visual area 17

Frontal eye field area 8

III nerve Edinger – Wesphal nucleus

Ciliary muscles; spinchter pupillae & Medial rectus

c. Otolith organ:

- two sac swellings o saccule o utricle - Utricle communicates with saccules by means of ductus endolymphaticus - Utricle and saccule contain a projecting ridge, the macula - Covering the projecting ridge is 30 – 150 long stiff hair – cupla terminalis - One end long non-motile hair is kinocillium - Progressive increase in height is stereocilia

Functioning; - Saccule and utricle provide information about linear acceleration and change in head position - Saccules are affected by a lateral tilt of head - Utricle are affected by nodding the head up and down. d. Jugular pulse;

- there is no valve at the junction of superior vena cava and right atrium - so the right atrial pressure changes are transmitted to jugular vein in neck - they produce 3 positive waves and 3 negative waves - Positive waves are a,c,v and negative waves are x, x1 and y

‗a‘ wave – due to atrial systole

‗c‘ wave – bulging of tricuspic valve into right atrium during isovolumetric contraction phase

‗v‘ wave – due to rise in atrial pressure before the tricuspid valve opens during diastole. e. P –R interval

- interval from the beginning of ‗p‘ wave the beginning of Q or R wave - it represents atrial depolarization plus conduction time to bundle of His - Normal duration 0.12 sec to 0.16 sec - If duration is more than 0.2 sec indicates delayed conduction o Eg. Incomplete heart block - Duration less than 012 sec indicate impulses arised from AV node. f. Chyne – stokes breathing:

- it is a type of periodic breathing - in this phase of hyperventilation is followed by apnea - waxing and wanning of waves occurs alternatetively - it is of gradual onset - Causes o Physiological . Voluntary hyperventilation . High altitude o Pathological . Brain damage . Uremia g. Buffer nerves

The nerves innervating the baroreceptors aortic and carotid sinus are buffer nerves

BP raises

Baroreceptor discharge increases

Inhibition of VMC

Stimulation of CVC

Fall in sypmpathtetic activity & raise in vagal activity

Prevent rise in BP

Hence, hering‘s nerve (branch of glossopharyngeal nerve ) and vagus nerve are known as Buffer nerves.

h. Dyspnoeic index

- Maximum amount of air that can be breathed in and out above normal ventilation. - MVV – PV - It is usually expressed in percentage as (MVV – PV) / MVV x 100 - normal range >= 60 – 70 % (usually 90 %) - < 60 % represents dyspnoea i. Nystagmus

When a subjects ‗s gaze is fixed at a stationary object, the eye balls are not still (without motion), there are continuous jerky movements (nystagmus)

- Types o Physiological / occulovestibular nystagmus o Pathological nystagmus Eg. Cerebellar lesions

j. Cushing’s reflex;

Increase in intracranial tension above 33 mmHg

Decreases blood supply to medulla & hypercapnea

Stimulates VMC

Restores BP by increased Sympathetic activity

HR decreases

Paper IV April 2001 Sub code: 4054

1. Hypoxia and its types:

Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole (generalized hypoxia) or a region of the body (tissue hypoxia) is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise. A mismatch between oxygen supply and its demand at the cellular level may result in a hypoxic condition. Hypoxia in which there is complete deprivation of oxygen supply is referred to as anoxia.

Hypoxic hypoxia is a generalized hypoxia, an inadequate supply of oxygen to the body as a whole. The term "hypoxic hypoxia" specifies hypoxia caused by low partial pressure of oxygen in arterial blood. In the other causes of hypoxia that follow, the partial pressure of oxygen in arterial blood is normal. Hypoxic hypoxia may be due to: o Low partial pressure of atmospheric oxygen such as found at high altitude or by replacement of oxygen in the breathing mix either accidentally as in the modified atmosphere of a sewer or intentionally as in the recreational use of nitrous oxide. o Low partial pressure of oxygen in the lungs when switching from inhaled anaesthesia to atmospheric air, due to the Fink effect, or diffusion hypoxia. o A decrease in oxygen saturation of the blood caused by sleep apnea or hypopnea o Inadequate pulmonary ventilation (e.g., in chronic obstructive pulmonary disease or respiratory arrest). o Shunts in the pulmonary circulation or a right-to-left shunt in the heart. Shunts can be caused by collapsed alveoli that are still perfused or a block in ventilation to an area of the lung. Whatever the mechanism, blood meant for the pulmonary system is not ventilated and so no gas exchange occurs (the ventilation/perfusion ratio is zero). Normal anatomical shunt occurs in everyone, because of the Thebesian vessels which empty into the left ventricle and the bronchial circulation which supplies the bronchi with oxygen. o hypemic hypoxia in which arterial oxygen pressure is normal, but total oxygen content of the blood is reduced. o Hypoxia when the blood fails to deliver oxygen to target tissues. . Carbon monoxide poisoning which inhibits the ability of hemoglobin to release the oxygen bound to it. . Methaemoglobinaemia in which an abnormal version of hemoglobin accumulates in the blood . Histotoxic hypoxia in which quantity of oxygen reaching the cells is normal, but the cells are unable to effectively use the oxygen due to disabled oxidative phosphorylation enzymes. The effects of drinking alcoholic beverages is a common example. . Ischemic, or stagnant hypoxia in which there is a local restriction in the flow of otherwise well-oxygenated blood. The oxygen supplied to the region of the body is then insufficient for its needs. Examples are cerebral ischemia, ischemic heart disease and Intrauterine hypoxia, which is an unchallenged cause of perinatal death.

Acclimatization to Low PO2 A person remaining at high altitudes for days, weeks, or years becomes more and more acclimatized to the low Po2, so that it causes fewer deleterious effects on the body. And it becomes possible for the person to work harder without hypoxic effects or to ascend to still higher altitudes. The principal means by which acclimatization comes about are (1) a great increase in pulmonary ventilation, (2) increased numbers of red blood cells, (3)increased diffusing capacity of the lungs, (4) increased vascularity of the peripheral tissues, and (5) increased ability of the tissue cells to use oxygen despite low Po2

2. a) Cardiac Catherization

Cardiac catheterization (heart cath) is the insertion of a catheter into a chamber or vessel of the heart. This is done for both investigational and interventional purposes. Subsets of this technique are mainly coronary catheterization, involving the catheterization of the coronary arteries, and catheterization of cardiac chambers and valves.

Indications for investigational use

This technique has several goals:

confirm the presence of a suspected heart ailment quantify the severity of the disease and its effect on the heart seek out the cause of a symptom such as shortness of breath or signs of cardiac insufficiency make a patient assessment prior to heart surgery

Investigative techniques used with coronary catheterization

to measure intracardiac and intravascular blood pressures to take tissue samples for biopsy to inject various agents for measuring blood flow in the heart; also to detect and quantify the presence of an intracardiac shunt to inject contrast agents in order to study the shape of the heart vessels and chambers and how they change as the heart beats b) P- R Interval

Repeated : March 02, Sept 02 C) Periodic Breathing

Repeated : Aug 04, 08 d) Oxygen dissociation curve:

Repeated : Feb 2005

3. Thalamus – nucleus, connections and functions.

The thalamus is a midline symmetrical structure within the brains of vertebrates including humans, situated between the cerebral cortex and midbrain. Its function includes relaying sensory and motor signals to the cerebral cortex, along with the regulation of consciousness, sleep, and alertness. The thalamus surrounds the third ventricle. It is the main product of the embryonic diencephalon.

Thalamic nuclei

Nuclei of the thalamus

The thalamus is part of a nuclear complex structured of four parts, the hypothalamus, epithalamus, ventral thalamus, and dorsal thalamus.

Derivatives of the diencephalon also include the dorsally-located epithalamus (essentially the habenula and annexes) and the perithalamus (prethalamus formerly described as ventral thalamus) containing the zona incerta and the "reticulate nucleus" (not the reticular, term of confusion). Due to their different ontogenetic origins, the epithalamus and the perithalamus are formally distinguished from the thalamus proper.

The thalamus comprises a system of lamellae (made up of myelinated fibers) separating different thalamic subparts. Other areas are defined by distinct clusters of neurons, such as the periventricular gray, the intralaminar elements, the "nucleus limitans", and others.[6] These latter structures, different in structure from the major part of the thalamus, have been grouped together into the allothalamus as opposed to the isothalamus. This distinction simplifies the global description of the thalamus.

Connections

The thalamus is connected to the spinal cord via the spinothalamic tract.

The thalamus is manifoldly connected to the hippocampus via the mammillo-thalamic tract, this tract comprises the mammilary body and fornix.

The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch. There are two main parts: the lateral spinothalamic tract, which transmits pain and temperature, and the anterior (or ventral) spinothalamic tract, which transmits crude touch and pressure.

Function

The thalamus has multiple functions. It may be thought of as a kind of switchboard of information. It is generally believed to act as a relay between a variety of subcortical areas and the cerebral cortex. In particular, every sensory system (with the exception of the olfactory system) includes a thalamic nucleus that receives sensory signals and sends them to the associated primary cortical area. For the visual system, for example, inputs from the retina are sent to the lateral geniculate nucleus of the thalamus, which in turn projects to the primary visual cortex (area V1) in the occipital lobe. The thalamus is believed to both process sensory information as well as relay it—each of the primary sensory relay areas receives strong "back projections" from the cerebral cortex. Similarly the medial geniculate nucleus acts as a key auditory relay between the inferior colliculus of the midbrain and the primary auditory cortex, and the ventral posterior nucleus is a key somatosensory relay, which sends touch and proprioceptive information to the primary somatosensory cortex. The thalamus also plays an important role in regulating states of sleep and wakefulness.[9] Thalamic nuclei have strong reciprocal connections with the cerebral cortex, forming thalamo- cortico-thalamic circuits that are believed to be involved with consciousness. The thalamus plays a major role in regulating arousal, the level of awareness, and activity. Damage to the thalamus can lead to permanent coma.

The role of the thalamus in the more anterior pallidal and nigral territories in the basal ganglia system disturbances is recognized but still poorly understood. The contribution of the thalamus to vestibular or to tectal functions is almost ignored. The thalamus has been thought of as a "relay" that simply forwards signals to the cerebral cortex. Newer research suggests that thalamic function is more selective.[10] Many different functions are linked to various regions of the thalamus. This is the case for many of the sensory systems (except for the olfactory system), such as the auditory, somatic, visceral, gustatory and visual systems where localized lesions provoke specific sensory deficits. A major role of the thalamus is devoted to "motor" systems. The thalamus is functionally connected to the hippocampus as part of the extended hippocampal system at the thalamic anterior nuclei with respect to spatial memory and spatial sensory datum they are crucial for human episodic memory and rodent event memory There is support for the hypothesis that thalamic regions connection to particular parts of the mesio-temporal lobe provide differentiation of the functioning of recollective and familiarity memory.

The neuronal information processes necessary for motor control were proposed as a network involving the thalamus as a subcortical motor centre. Through investigations of the anatomy of the brains of primates the nature of the interconnected tissues of the cerebellum to the multiple motor cortices suggested that the thalamus fulfills a key function in providing the specific channels from the basal ganglia and cerebellum to the cortical motor areas. In an investigation of the saccade and antisaccade motor response in three monkeys, the thalamic regions were found to be involved in the generation of antisaccade eye-movement.

4) a) Attenuation Reflex

The acoustic reflex (or stapedius reflex, attenuation reflex, or auditory reflex) is an involuntary muscle contraction that occurs in the middle ear of mammals in response to high- intensity sound stimuli.

When presented with a high-intensity sound stimulus, the stapedius and tensor tympani muscles of the ossicles contract. The stapedius pulls the stapes (stirrup) of the middle ear away from the oval window of the cochlea and the tensor tympani muscle pulls the malleus (hammer) away from ear drum. The reflex decreases the transmission of vibrational energy to the cochlea, where it is converted into electrical impulses to be processed by the brain. The acoustic reflex normally occurs only at relatively high intensities; activation for quieter sounds can indicate ear dysfunction.The pathway involved in the acoustic reflex is complex and can potentially involve the ossicular chain (malleus, incus and stapes), the cochlea itself (organ of hearing), and from there, the auditory nerve, brain stem and facial nerve. Even this represents a simplification. Consequently, the absence of an acoustic reflex, by itself, may not be conclusive in identifying the source of the problem. b) Macula Lutea

The macula or macula lutea is an oval-shaped highly pigmented yellow spot near the center of the retina of the human eye. It has a diameter of around 5 mm and is often histologically defined as having two or more layers of ganglion cells. Near its center is the fovea, a small pit that contains the largest concentration of cone cells in the eye and is responsible for central, high resolution vision. The macula also contains the parafovea and perifovea.

Because the macula is yellow in colour it absorbs excess blue and ultraviolet light that enter the eye, and acts as a natural sunblock (analogous to sunglasses) for this area of the retina. The yellow colour comes from its content of lutein and zeaxanthin, which are yellow xanthophyll carotenoids, derived from the diet. Zeaxanthin predominates at the macula, while lutein predominates elsewhere in the retina. There is some evidence that these carotenoids protect the pigmented region from some types of macular degeneration.

Structures in the macula are specialized for high acuity vision. Within the macula are the fovea and foveola which contain a high density of cones c) Composition and functions of CSF:

Cerebrospinal fluid (CSF) is a clear colorless bodily fluid produced in the choroid plexus of the brain. It acts as a cushion or buffer for the cortex, providing a basic mechanical and immunological protection to the brain inside the skull and serves a vital function in cerebral autoregulation of cerebral blood flow.

The CSF occupies the subarachnoid space (the space between the arachnoid mater and the pia mater) and the ventricular system around and inside the brain and spinal cord. It constitutes the content of the ventricles, cisterns, and sulci of the brain, as well as the central canal of the spinal cord.

Functions

CSF serves four primary purposes:

1. Buoyancy: The actual mass of the human brain is about 1400 grams; however, the net weight of the brain suspended in the CSF is equivalent to a mass of 25 grams.[1] The brain therefore exists in neutral buoyancy, which allows the brain to maintain its density without being impaired by its own weight, which would cut off blood supply and kill neurons in the lower sections without CSF. 2. Protection: CSF protects the brain tissue from injury when jolted or hit. In certain situations such as auto accidents or sports injuries, the CSF cannot protect the brain from forced contact with the skull case, causing hemorrhaging, brain damage, and sometimes death. 3. Chemical stability: CSF flows throughout the inner ventricular system in the brain and is absorbed back into the bloodstream, rinsing the metabolic waste from the central nervous system through the blood–brain barrier. This allows for homeostatic regulation of the distribution of neuroendocrine factors, to which slight changes can cause problems or damage to the nervous system. For example, high glycine concentration disrupts temperature and blood pressure control, and high CSF pH causes dizziness and syncope. To use Davson's term, the CSF has a "sink action" by which the various substances formed in the nervous tissue during its metabolic activity diffuse rapidly into the CSF and are thus removed into the bloodstream as CSF is absorbed. 4. Prevention of brain ischemia: The prevention of brain ischemia is made by decreasing the amount of CSF in the limited space inside the skull. This decreases total intracranial pressure and facilitates blood perfusion. d) Taste pathway:

The primary gustatory cortex is a brain structure responsible for the perception of taste. It consists of two substructures: the anterior insula on the insular lobe and the frontal operculum on the inferior frontal gyrus of the frontal lobe.

The Taste Pathway

Transduction occurs when different taste substances cause a change in the flow of ions across the membrane of a taste cell. Different substances affect the membrane in different ways. o Bitter and sweet substances bind into receptor sites which release other substances into the cell. o Sour substances contain H+ ions that block channels in the membrane. o Salty substances break up into Na+ ions which flow through the membrane directly into the cell. o Electrical signals generated in the taste cells are transmitted in three pathways: o The chorda tympani nerve conducts signals from the front and sides of the tongue. o The glosso-pharyngeal nerve conducts signals from the back of the tongue. o The vagus nerve conducts taste signals from the mouth and the larynx. These three nerves make connections in the brain stem in the nucleus of the solitary tract (NST) before going on to the thalamus and then to two regions of the frontal lobe (the insula and the frontal operculum cortex).

Paper IV November 2001 Sub code 4054

1. Pressure tracings of left atrial and ventricular events in cardiac cycle

Sequence of changes in pressure and flow in the heart chambers and blood vessels in between two subsequent cardiac contractions.

Left ventricular pressure graph:

AB segment: atrial contraction

BC segment: isovolumetric contraction

CD segment: ventricular ejection phase

DE segment: isovolumetric relaxation

EF segment: initial rapid & slow ventricular filling phase

Left atrial pressur curve:

3 positive (a,c,v) and 3 negative (x, x1 and y) characterictic waves

a- atrial systole

c – bulging of tricuspid valve into right atrium during isovolumetric contraction

v- before tricuspid valve opens during diastole. 2. a) Chemorecpetors in regulation of respiration:

Chemorecetors:

- Peripheral chemoreceptors - Medullary ( or central ) chemo receptors

(i) Peripheral chemoreceptors: a. Carotid & aortic bodies b. They contain type I & II glomus cells c. They senses i. Decrease in pO2 ii. Increase in pCo2 levels

d. Stimuli taken by Hering‘s (Glossopharyngeal nerve) and vagus to inspiratory center at medulla to cause increase depth and rate of inspiratin (ii) Central ( or medullary) chemoreceptors:

- H+ ions cannot pass through blood brain barrier to enter medullary chemosenstitive area - So CO2 enters BBB easily and in CSF - CO2 + H2O ------> H+ + HCO3- - H+ ions are potent stimuli for increasing rate and depth of respiration - Pulmonary and myocardial receptors - Bezold Jarisch reflex

b. Voluntary hyperventilation.

Voluntary hyperventilation for 2 min produces apnea.

Mechainsm:

Hyperventilaton

Excess CO2 washout

No stimuli for respiration

C02 accumulation apnea

Stimulate respiratory center

Ventilation

c. Arterial baroreceptors.

- these are the stretch receptors stimulated by stretch of arterial wall - location: o Carotid sinus – birfurcation of carotid artery o Aortic sinus – arch of aorta - Innervation: o Carotid sinus: hering‘s nerve branch of glassopharyngeal nerve o Aortic sinus; Vagus nerve

Mechanism:

Rise in BP

Arterial wall stretches

Impulses carried by buffer nerves

Suppression of VMC Stimulation of CVC

Peripheral resistance decreases HR decreases

Diastolic BP decreases Systolic BP decreases

BP comes back to normal

d. Dark adaptation:

- After entering a dark room, visual perception improves quickly at first and then slowly. - The decrease in visual threshold or increased sensitivity of eye to light is called cark adaptation. o Fast response o Slow response

(i) Fast response

- first drop in visual threshold is rapid and is due to dark adaptation of cones - paradoxical adapatatiom

(ii) Slow response - further drop in visual threshold over period of 25 mins - due to adaptation of rods in peripheral retina. - Changes in dark adaptation o Mydriasis o Cones to rods o Resynthesis of rhodopsin.

3. Connectoins and functions of basal ganglia:

- Mass of grey matter (nuclei) in forebrain and upper part of brain stem. - It includes o Caudate nucleus o Putamen o Globus pallidus or pallidum o Sub thalamic nucleus o Substantia nigra

Connections of Basal Ganglia:

A) afferent connection are excitatory (cholinergic) a. corticostriate projection b. thalamostriate fibers B) Internuclear connections: a. Dopaminergic nigrostriatal tract b. GABA iergic inhibitory projections C) Efferent connections: a. Via thalamic fasiculus to vent, lateral and ant thalamus b. Ansa lenticularis tract.

Functions of basal ganglia: - involved in planning and programming the movement - it increases during slow, steady, damp movt saccadiac movement - inhibits the stretch reflex ( muscle tone) throughout the body - Neostriatum regulates subconscious gross movemtents - Caudate nucleus play an important role in coagnitive process - Globys pallidus provides app muscle tone - Substantia nigra – center for co- ordination

Leisons of basal ganglia:

(i) Parkinson‘s disease:

Shaking palsy characterized by rigitdity, tremors (hyperkiniesia) & weakness of movements Cause:

Degeneration of sustantia nigra, decreased dopamine in striatonigral pathway c/f: - rigidity - static tremor - loss of associated movements - loss of facial expression - festinant gait

(ii) Chorea and athetosis:

- spontaneous involuntary movements - due to lesion in caudate nucleus.

4. a) Mechanism of stimulation of taste buds:

Receptor stimulation:

- substances dissolved in oral fluid - combine with receptors (gustatory cells) to produce generator potentials - Modalities or qualities of taste o Sweet, sour, salt & bitter recently umami

(i) Sour: a. acidic, contains H+ ions b. they stimulate by raising intracellular H+ by blocking K+ channels (ii) Salt: a. By influx of Na+ ions (iii) Bitter: a. Due to cations b. Coupled to G proteins & phospholipase to release Ca+ ions

(iv) Sweet: a. By Gs causing slosure of K+ channels. b. Travelling wave theory:

- also called place theory by von be bekesy - shows the basic pattern of movement of basilar membrane - the distance from stapes to the point of maximum height - it varies with intensity or frequency of vibration - high pitched wave – near base of cochlea - low pitched – near the apex c. Night blindness:

- blindness in dim light - decreased sensitivity of eue due to vit A deficiency - because Vit A is required for synthesi of retinine - prolonged Vit A deficiencies will lead to anatomical changes in rods.

Color blindness:

- Insenstive to colours - Three heads - Trichromats o Protonomaly o Deutronomaly o tritonomaly - Dichromats o Protonophia o Deutronopia o tritonophia - Monochromats

d. Sensory receptors:

-specialized modified nerve endings undergoes depolarization in response to specific stimulus Classification: Sherrington‘s classification

(i) Telereceptors: a. Hearing – cochlea b. Vision - retina (ii) Exteroreceptors a. Touch – merkels‘s disc (iii) Interoreceptors a. Proprioceptors (joint postion sense) – muscle spincle b. Visceroreceptors – Baroreceptors c. Chemoreceptors – eg. Carotid bodies

Paper IV March 2002 Sub code: 4054

1. Chemical regulation of respiration

Repeated refer: Nov 2001

2. a. short term regulation of BP

Repeated refer: Nov: 2001 b. Coronary circulation:

- Heart is supplied by 2 coronary arteries – right and left coronary arteries - Right coronary artery o Whole right atrium o Greater part of tight ventricle o Small left ventricle o Major conducting system - Left coronary artery o whole left atrium o greater left ventricle o small part of right ventricle

Venous drainage:

- superficial system o coronary sinus o greater cardiac vein o anterior cardiac vein - Deep system o Thebesian vessels

Measurement:

- Kety‘s method or nitrous oxide technique – modified fick‘s principle - Coronary angiography - Radionucleotide utilization technique

Characteristic features:

- normal flow: 250 ml / min or 60 – 80 ml / 100 gm / min - A – V O2 difference : 13 ml % - Coefficient of O2 utilization : 70 % - Coronary blood flow fluctuates during blood flow – shows phasic blood flow

Regulation of coronary blood flow:

a. chemical factors – Berne‘s hypothesis b. Autoregualtion c. Neural factors c. Factors regulating cardiac output:

Cardiac output = heart rate x stroke volume

A) control of HR or extrinsic regulation: a. sympathetic – increases HR b. parasympathetic - decreases HR Medullary centre – VMC & CVC influences

B) Control of stroke volume: Intrinsic regulation

(i) Heterometric regulation 1. Frank starling‘s law on EDV 2. Pre 0 load based on EDV

(ii) Homometric regulation 1. factors influencing myocardial contractability increases Co eg. Catecholamines, sympathetic nervous system Drugs – xanthine eg. Caffine

d. Electrocardiagram.

The record of electrical activity of heart during cardiac cycle is called ECG.

Normal ECG: - x axis : 1 mm – 0.04 sec - y axis : 1 mm – 0.1 mV

ECG in lead II:

‗P‘ Wave:

- atrial depolarisation - duration 0.1 sec: amplitude 0.5 mV

‗QRS‘ complex:

- ventricular depolarization - Q – wave : 0.2 mV; 0.04 sec - R wave – ventricular systole 0.08 sec – 0.12 sec; 1.5 to 2 mV

‗PR‘ interval:

- 0.13 to 0.16 sec - Prolonged in AV nodal block

‗ST‘ segment:

- isoelectric

ECG leads:

- Unipolar leads o Chest leads – V1, V2, V3, V4, V5 and V6 o Limb leads VL, VF, FR - Bipolar leads o Limb lead I, o Limb lead II, o Limb lead III

3. Pathway for fine touch:

Fine touch is carried by dorsal column pathways Fasciculus gracillus and cuneatus

Origin:

Ist order neurons originate from posterior root ganglia

Fasiculus gracilus afferents from lower half

Fasiculus cuneatus afferents from upper half.

Course:

1 order neuron - after it enters spinal cord it ascends on the same side, it represented as sacral to cervical as medical to lateral in spinal cord. - At the level of medulla they synapse with nucleus cuneatus and nucleus gracillus - Then they cross over to opposite side as internal arcuate fibers - Then as medical lemniscus they ( 2 order neurons ) ascend upto thalamus. - 3 order neurons ascent from the VPL nucleus of thalamus to parietal lobe area 3,1,2

Sensory homunculus:

- sensation of different parts of the body is represented in post central gyrus. - Larger area is represented fro thumb, lips and fingers.

4. a. Dark adaptation

Repeated refer: Aug 2008, Nov 2001 b. Organ of corti.

- Receptor for hearing - Located on basilar membrane from base to apex of cochlea - It consist of : o Inner hair cells o Inner phalangeal cells o Hensen‘s cell or supporting cells o Cells of Claudius o Outer pillar cells o Outer hair cells or Deiter‘s cells

c. Errors of refraction

Repeated refer: Feb 2007, 08 d. Taste pathway

Repeated refer: April 2001, Feb 2005

Paper IV Sept 2002 Sub code: 4054

1. Nervous regulation of respiration and Hering brewer reflex.

Repeated Refer: Aug 2009

2. a. Sino aortic mechanism.

Repeated refer: March 2002, Feb 2011

b. cerebral circulation

Physiological anatomy:

Arterial supply: The brain is supplied by 2 arteries:

(i) Two internal carotid arteries, and (ii) Two vertebral arteries, which united to form basilar artery.

Basilar artery along with two internal carotid arteries forms Circle of willis which gives origin to 6 large vessels and provides entire blood supply to the brain.

Venous drainage: Venous drainage from the brain is carried out by two systems: Superficial and deep veins. Veins from these two systems anastomose and open into the venous sinusus(which lie between the dura mater and bone). These veins have no valves and are kept open by the structures of the dura around their orifices. Venous drainage of the brain is mainly:

(i) via internal jugular vein (ii) by channels which join the vertebral venous plexus, and (iii) by anastomoses with the orbital and pterygoid plexus.

Innervation of cerebral blood vessels: (i) Sympathetic supply (ii) Para sympathetic supply

General features:

(i) Adult brain weighs 1400 gms; 60 %( 840 gm) is comprised of white matter and remaining 40% (560 gm) is grey matter. (ii) Cerebral blood flow is 750 ml/min or 50-60 ml/ min/100 gm. Critical flow level is approx. 18 ml/min/100 gm as flow less than this produces unconsciousness. (iii) Cerebral o2 consumption is 3.3 ml/100gm/min or 45 ml/min i.e.20% of the whole body at rest. (iv) No change in the blood supply to the brain during the exercise. (v) The brain is extremely sensitive to hypoxia and occlusion of its blood supply within 10 sec produces unconsciousness.

Measurement of cerebral blood flow:

A. Kety method or nitrous oxide Technique

It is based on Fick principle

B. 133 Xe Clearance curve Technique Scintillation detectors are used in this technique.

Factors affecting the cerebral blood flow:

Arterial blood pressure

Intra cranial pressure

Resistance

Diameter of blood vessel

Viscosity of the blood

Regulation of cerebral blood flow:

Autoregulation

Metabolic regulation-co2, o2, pH etc...

Role of basal myogenic tone of blood vessels

Role of intracranial pressure

Nervous regulation

c. ECG in limb lead II

Repeated refer: March 2002

d. Factors influencing heart rate:

Control of Heart Rhythmicity and Impulse Conduction by the Cardiac Nerves:

The Sympathetic and Parasympathetic Nerves

- The heart is supplied with both sympathetic and parasympathetic nerves.

- The parasympathetic nerves (the vagi) are distributed mainly to the S-A and A-V nodes, to a lesser extent to the muscle of the two atria, and very little directly to the ventricular muscle.

- The sympathetic nerves, conversely, are distributed to all parts of the heart, with strong representation to the ventricular muscle as well as to all the other areas.

Parasympathetic (Vagal) Stimulation Can Slow or Even Block Cardiac Rhythm and Conduction— “Ventricular Escape.”

- Stimulation of the parasympathetic nerves to the heart (the vagi) causes the hormone acetylcholine to be released at the vagal endings. - This hormone has two major effects on the heart. First, it decreases the rate of rhythm of the sinus node, and second, it decreases the excitability of the A-V junctional fibers between the atrial musculature and the A-V node,

- thereby slowing transmission of the cardiac impulse into the ventricles.

Effect of Sympathetic Stimulation on Cardiac Rhythm and Conduction.

-Sympathetic stimulation causes essentially the opposite effects on the heart to those caused by vagalstimulation, as follows:

- First, it increases the rate of sinus nodal discharge. Second, it increases the rate of conduction as well as the level of excitability in all portions of the heart.

3. Pain pathway and thalamic syndrome:

Repeated refer: Feb 2012

4. a. Visual acuity.

- Theoretically, light from a distant point source, when focused on the retina, should be infinitely small.

- However, because the lens system of the eye is never perfect, such a retinal spot ordinarily has a total diameter of about 11 micrometers, even with maximal resolutionof the normal eye optical system.

- The spot is brightest in its center and shades off gradually toward the edges

- The average diameter of the cones in the fovea of the retina—the central part of the retina, where vision is most highly developed—is about 1.5 micrometers, which is one seventh the diameter of the spot of light.

- Nevertheless, because the spot of light has a bright center point and shaded edges, a person can normally distinguish two separate points if their centers lie as much as 2 micrometers apart on the retina, which is slightly greater than the width of a foveal cone.

- The normal visual acuity of the human eye for discriminating between point sources of light is about 25seconds of arc. That is, when light rays from two separate points strike the eye with an angle of at least 25 seconds between them, they can usually be recognized

as two points instead of one

b. Basilar membrane

-The cochlea is a system of coiled tubes.

- It consists of three tubes coiled side by side:

(1) the scala vestibuli,

(2) the scala media, and

(3) the scala tympani

- . The scala vestibuli and scala media are separated from each other by Reissner’s membrane

- The scala tympani and scala media are separated from each other by the basilar membrane. On the surface of the basilar membrane lies the organ of Corti.

- It contains a series of electromechanically sensitive cells, the hair cells.

- The basilar membrane is a fibrous membrane that separates the scala media from the scala tympani. - It contains 20,000 to 30,000 basilar fibers that project from the bony center of the cochlea, the modiolus, toward the outer wall. - These fibers are stiff, elastic, reedlike structures that are fixed at their basal ends in the central bony structure of the cochlea (the modiolus) but are not fixed at their distal ends, except that the distal ends are embedded in the loose basilar membrane.

c. Color blindness:

Repeated refer: Nov 2011, Aug 2007

d. Accomodation of near vision:

Repeated refer: Oct 2003, Sep 2002, Feb 2005

Oct-2003 sub code: 4054

I) Eassy

1) Blood pressure.

Refer: Aug 2008, March 2002

2) Vestibular apparatus in posture and equilibrium:

 The vestibular apparatus is the sensory organ for detecting sensations of equilibrium.  It is encased in a system of bony tubes and chambers located in the petrous portion of the temporal bone, called the bony labyrinth.  Within this system are membranous tubes and chambers called the membranous labyrinth.  The membranous labyrinth is the functional part of the vestibular apparatus.  It is composed mainly of the cochlea (ductus cochlearis); three semicircular canals; and two large chambers, the utricle and saccule.  The cochlea is the major sensory organ for hearing and has little to do with equilibrium. However, the semicircular canals, the utricle, and the saccule are all integral parts of the equilibrium mechanism.

“Maculae”—Sensory Organs of the Utricle and Saccule for Detecting Orientation of the Head with Respect to Gravity:

- Located on the inside surface of each utricle and saccule, small sensory area slightly over 2 millimeters in diameter called a macula.

- The macula of the utricle lies mainly in the horizontal plane on the inferior surface of the utricle and plays an important role in determining orientation of the head when the head is upright.

- Conversely, the macula of the saccule is located mainly in a vertical plane and signals head orientation when the person is lying down.

- Each macula is covered by a gelatinous layer in which many small calcium carbonate crystals called statoconia are embedded

- .Also in the macula are thousands of hair cells, these project cilia up into the gelatinous layer. - The bases and sides of the hair cells synapse with sensory endings of the vestibular nerve.

- The calcified statoconia have a specific gravity two to three times the specific gravity of the surrounding fluid and tissues.

- The weight of the statoconia bends the cilia in the direction of gravitational pull.

Function of the Utricle and Saccule in the Maintenance of Static Equilibrium

- It is especially important that the hair cells are all oriented in different directions in the maculae of the utricles and saccules, so that with different positions of the head, different hair cells become stimulated.

- The “patterns” of stimulation of the different hair cells apprise the brain of the position of the head with respect to the pull of gravity. In turn, the vestibular, cerebellar, and reticular motor nerve systems of the brain excite appropriate postural muscles to maintain proper equilibrium.

- This utricle and saccule system functions extremely effectively for maintaining equilibrium when the head is in the near-vertical position.

“Predictive” Function of the Semicircular Duct System in the Maintenance of Equilibrium

- All they detect is that the person’s head is beginning or stopping to rotate in one direction or another.

- Therefore, the function of the semicircular ducts is not to maintain static equilibrium or tmaintain equilibrium during steady directional or rotational movements.

- Yet loss of function of the semicircular ducts does cause a person to have poor equilibrium when attempting to perform rapid, intricate changing body movements.

Vestibular Mechanisms for Stabilizing the Eyes

- When a person changes his or her direction of movement rapidly or even leans the head sideways, forward, or backward, it would be impossible to maintain a stable image on the retinas unless the person had some automatic control mechanism to stabilize the direction of the eyes’ gaze.

II) Short Notes:

a) Accommodation Refer: Sept 02, Feb 05

b) Visceral pain:  Pain from visceral structures is poorly localized, unpleasant and associated with nausea and autonomic changes.  It often radiates or referred to other sites Some common causes of visceral pain are:

 Excessive distension of hollow viscera, such as the intestine or urinary bladder  Intestinal obstruction, by the contraction of the distended intestine above the obstruction  Spasm of a portion of a gut or any hollow viscus such as gall bladder, urinary bladder,ureter.  Essentially all visceral pain that originates in the thoracic and abdominal cavities is transmitted through small type C pain fibers and, therefore, can transmit only the chronic aching-suffering type of pain.  Pain from the different viscera is frequently difficult to localize, for a number of reasons. Therefore any pain that originates internally can be localized only generally.  Second, sensations from the abdomen and thorax are transmitted through two pathways to the central nervous system—the true visceral pathway and the parietal pathway.  True visceral pain is transmitted via pain sensory fibers within the autonomic nerve bundles, and the sensations are referred to surface areas of the body often far from the painful organ.  Conversely, parietal sensations are conducted directly into local spinal nerves from the parietal peritoneum, pleura, or pericardium and these sensations are usually localized directly over the painful area.

c) Sensory cortex:

 From the specific sensory nuclei of thalamus, neurons project in a highly specific way to the two somatic sensory areas of the cortex: primary and secondary sensory areas.  The anterior half of the parietal lobe is concerned almost entirely with reception and interpretation of somatosensory signals.  But the posterior half of the parietal lobe provides still higher levels of interpretation. Visual signals terminate in the occipital lobe, and auditory signals in the temporal lobe.

Primary sensory area: It is located in the postcentral gyrus cointaing the brodmann’s area 3, 1, 2

Secondary sensory area: It is located in the parietal cortex and is mostly buried in the superior wall of the sylvian fissure

d) Total peripheral resistance in vascular system

The vessels which offer resistance to blood flow towards the capillaries are called pre capillary resistance vessels.

Eg. Arterioles, meta arterioles and pre capillary sphincters

Arterioles offer maximal resistance to the blood flow towards the capillaries and thus are the main sight of peripheral resistance.

The overall mechanism by which increased extracellular fluid volume elevates arterial pressure. The sequential events are

(1) increased extracellular fluid volume

(2) increases the blood volume, which

(3) increases the mean circulatory filling pressure, which

(4) increases venous return of blood to the heart, which

(5) increases cardiac output, which

(6) increases arterial pressure.

Note especially in this schema the two ways in which an increase in cardiac output can increase the arterial pressure.

One of these is the direct effect of increased cardiac output to increase the pressure, and the other is an indirect effect to raise total peripheral vascular resistance through autoregulation of blood flow.

e) Acclimatization at high attitude Repeated refer: Feb 05, March 02

f) Compliance of lungs Repeated refer: Aug 2009, Feb 11

g) Functions of middle ear Repeated refer: Feb 2007, 05

h) Associative learning

Associative learning is the process by which an association between two stimuli or a behavior and a stimulus is learned. The two forms of associative learning are classical and operant conditioning.

In the former a previously neutral stimulus is repeatedly presented together with a reflex eliciting stimuli until eventually the neutral stimulus will elicit a response on its own. In operant conditioning a certain behavior is either reinforced or punished which results in an altered probability that the behavior will happen again.

Operant conditioning is the use of consequences to modify the occurrence and form of behavior. Operant conditioning is distinguished from Pavlovian conditioning in that operant conditioning uses reinforcement/punishment to alter an action-outcome association.

In contrast Pavlovian conditioning involves strengthening of the stimulus-outcome association. Classical conditioning (also Pavlovian conditioning or respondent conditioning) is a form of learning in which one stimulus, the conditioned stimulus or CS, comes to signal the occurrence of a second stimulus, the unconditioned stimulus or US. The US is usually a biologically significant stimulus such as food or pain that elicits a response from the start; this is called the unconditioned response or UR. The CS usually produces no particular response at first, but after conditioning it elicits the conditioned response or CR. Classical conditioning differs from operant or instrumental conditioning, in which behavior emitted by the organism is strengthened or weakened by its consequences.

i) Righting reflexes By means of the righting reflexes the midbrain animal can bring its head right way up and get the body into the erect position under all circumstances. They are:

1. Labyrinthine righting reflex – impulses from saccules which lead reflexly to righting of the head.

2. Body righting reflex – asymmetric stimulation of the deep structures in the body wall reflexly rights the head.

3. Neck righting reflex. – It brings the thorax and lumbar region successively into the upright position.

4. Limbs righting reflex – posture of the limbs is largely attained by impulses arising from the limb muscle themselves.

5. Optical righting reflex. - With the visual cortex intact righting of the head is also brought about reflexly by means of optical impulses.

j) Control of food intake. Repeated refer: Aug 2005, 07

Paper IV August 2004 Sub code 4054

I Essay:

1) Oxygen transport in the body and oxygen dissociation curve:

Oxygen is carried as two forms: a) Dissolved form: - 0.3 ml per 100 ml of blood per 100 mmHg - dissolved O2 increases in linearity with arterial pO2. b) Combination with haemoglobin: - each Hb has 4 heme parts - iron is present in ferrous form. - Each Hb combines with 2 moles of O2 hence 1 Hb carries 8 moles of O2. - Oxygenation & deoxygenation of Hb is so rapid.

The O2 carrying capacity of Hb os given by oxygen dissociation curve.

- It is the curve relating percentage O2 saturation of haemoglobin to the pO2. - It has a characteristic sigmoid curve.

- the combination of O2 to Hb is step by step process so the curve is sigmoid in nature. - P50 – the partial pressure of oxygen at which Hb saturation is 50% it is 27 mmHg.

Shift to right: - decrease in pH - increase in body temperature - increase in 2,3 DPG

Shift to left: - Increase in pH - Decreased body temperature - Decrease in 2,3 DPG.

2) Visual pathway and lesions at various levels:

- Visual fibers arise from layer of nerve cells (bipolar & ganglion cells) in retina.

(i) First order Neurons:

- from bipolar cells whose dentrites synapse with photorecepetors (rods & cones)

(ii) Second order neurons:

- axons of ganglion cells pass backwards along optic nerve to optic chiasma. - Partial crossing of the fibers occur. - The two optic tracts are formed the left optic tract conveys fiber from left halves of both retina and the right optic tract from right halves of both retina. - Few fibers enter superior colliculus for visual reflexes. - Then to lateral geniculate body.

(iii) Thrid order neurons:

- optical radiations from LGB via internal capsule as geniculo calcrine tract to primary visual area (17).

- The principal visual pathways from the two retinas to the visual cortex. The visual nerve signals leave the retinas through the optic nerves

.- At the optic chiasm, the optic nerve fibers from the nasal halves of the retinas cross to the opposite sides, where they join the fibers from the opposite temporal retinas to form the optic tracts.

- The fibers of each optic tract then synapse in the dorsal lateral geniculate nucleus of the thalamus, and from there, geniculocalcarine fibers pass by way of the optic radiation (also called the geniculocalcarine tract) to the primary visual cortex in the calcarine fissure area of the medial occipital lobe.

- Visual fibers also pass to several older areas of the brain:

(1) from the optic tracts to the suprachiasmatic nucleus of the hypothalamus, presumably to control circadian rhythms that synchronize various physiologic changes of the body with night and day; (2) into the pretectal nuclei in the midbrain, to elicit reflex movements of the eyes to focus on objects of importance and to activate the pupillary light reflex; (3) into the superior colliculus, to control rapid directional movements of the two eyes; and (4) into the ventral lateral geniculate - nucleus of the thalamus and surrounding basal regions of the brain

II) a) Respiratory changes during moderate exercise:

(i) Pulmonary ventilation: (PV)

- During moderate exercise it increases to 15 – 18 times ie) 70 – 80 lit/min. - PV increases in parallel with the increase in O2 consumption (VO2 max). Mechanism: - Psychic stimulus - Afferent stimuli from propriceptors - Stimulation of carotid bodies - Accumulation of lactic acids

(ii) Pulmonary diffusion of O2:

- Increased by 3 times: o Increased blood perfusion o Opening of more capillaries.

(iii) oxygen consumption:

- Increases by 12 – 15 times o Increase in cardiac output o Increase in alveolar ventilation o Increase in capillary density. b) Origin & spread of cardiac impulse :

SA node ( pace maker of the heart ) 0.05 m / s

Internodal fibers 1.0 m/ s

Wenchebach Bachman Thorel

AV node 0.05 m / s

Bundle of His 1.0 m / s

Right Bundle Left Bundle branch 4.0 m /s

Purkinjee fibers Then the impulses spread into the ventricular muscles. C) Foetal Circulation:

Oxygenated blood from the mother

Placenta

Foetal liver

Abdominal IVC

IVC

Right atrium

Foramen ovale RV

LA Pulmonary trunk

Aorta Ductus arteriosus

Aorta

Descending aorta

Umblical artery into mothers Placenta

d) Refractory errors of eye:

Emmetropia (Normal Vision).

- The eye is considered to be normal, or ―emmetropic,‖ if parallel light rays from distant objects are in sharp focus on the retina when the ciliary muscle is completely relaxed. - This means that the emmetropic eye can see all distant objects clearly with its ciliary muscle relaxed. However, to focus objects at close range, the eye must contract its ciliary muscle and thereby provide appropriate degrees of accommodation.

Hypermetropia (sightedness)

- Hyperopia, which is also known as ―farsightedness,‖ is usually due to either an eyeball that is too short or, occasionally, a lens system that is too weak. - parallel light rays are not bent sufficiently by the relaxed lens system to come to focus by the time they reach the retina. - To overcome this abnormality, the ciliary muscle must contract to increase the strength of the lens. By using the mechanism of accommodation, a farsighted person is capable of focusing distant objects on the retina. - If the person has used only a small amount of strength in the ciliary muscle toaccommodate for the distant objects - In old age, when the lens becomes ―presbyopic,‖ a farsighted person is often unable to accommodate the lens sufficiently to focus even distant objects, much less near objects. - It can be corrected by convex lens

Myopia (Nearsightedness).

- In myopia, or ―nearsightedness,‖ when the ciliary muscle is completely relaxed, the light rays coming from distant objects are focused in front of the retina. - This is usually due to too long an eyeball, but it can result from too much refractive power in the lens system of the eye. - It can be corrected by concave lens

e) Cochlea:

- It is a coiled tube of 35 mm long. - It has 2.5 to 2.75 turns - Lumen is divided by two membranes o Reissner‘s membrane o Basilar membrane - Into three compartments o Scala vestibule o Scala tympani o Scala media - Scala tympani and vestibule communicate at the apex by small opening helicotrema - Scala tympani ends at round window and vestibuli ends at oval window. - The organ corti the receptor for hearing located on basilar membrane extending from the apex to cochlea. - Hair cells are innervated by nerve fibers of cochlear (auditory) division of VIII nerve.

f) Neuroglia;

- these are those that support the nerve cells. - They are about 10 times more than the neurons - They are capable for multiplying by mitosis - They are of 3 types:

(i) Microglia a. Phagocytic in nature b. Come from bone marrow and enter the CNS, meninges etc.

(ii) Astrocytes a. Found throughout the brain joining the blood vessels b. Function as supporting cells , for transport mechanisms and Blood brain barrier.

(iii) Oligodendroglia a. Cells that form myelin around the axon within CNS. g) Functions of limbic system:

(i) limbic system represents the primary area of control of autonomic functions. (ii) It is concerned with emotions of rage and fear (iii) It is involved in emotions (iv) It is concerned with behavioral aspects of hunger (v) Involved in olfaction and memory (vi) Concerned with sexual behavior (vii) Partial removal of neocortex and limbic system inhibits sexual behavior (viii) Bilateral destruction of amydaloid nuclei results in loss of memory. h) Mechanism of memory:

- Memory is the ability to recall the past events at conscious or unconscious levels - It is of two types: o Recent memory or short term memory – immediate recall of events o Remote or long term memory – memory of remote past - Physiological mechanisms o Encoding process involves hippocampus and the neighboring cortex o These connections contain cell bodies and fibers of cholinergic system o Protein synthesi and activation of genes is involved in process responsible for memory. o Increase in mRNA during learning process modify synaptic transmissions during memory

i) Humoural regulation of blood pressure:

Renin Angioitensin mechanism:

Decreased blood flow & perfusion

Renal ischemia

Renin released from JG apparatus

Angiotensinogen

Angiotensin I

Angiotensin II

Angiotensin III

Adrenal cortex direct effect on kidney Vasoconstriction

Aldosterone

Water and electrolyte retention

BP increases and normalized j) Artificial respiration:

- Holger nickelson method - Mouth to mouth respiration - Tank respirators - Ventilators

Paper IV August 2005 Sub code: 4054

I (1) Chemoreceptors and chemical regulation of respiration:

Repeated refer: Nov 2001

(2) Otolith organs – mechanism of action.

These are two sac like swellings, the saccule and utricle, a part of vestibular apparatus present inside the inner ear.

These are fluid filled membranous tubes connected with each other lie in tunnels in the temporal bone on each side of the head.

The utricle communicates with the saccule by means of the ductus endolymphaticus.

Both utricle and saccule contain a projecting ridge, the macula.

Structure of the receptor: the crista and macula

T he crista and macula are the specific receptors of the vestibular apparatus and have a similar structure.

Covering the projecting ridge is a tall columnar epithelium giving attachment to 30-150 long stiff projections called as hair cells, which project into a firm gelatinous material, the cupula terminalis.

Between the hair cells lie the fibers of origin of the vestibular division of the VIII nerve.

In the saccule and utricle, the cupula contains many chalky (calcium carbonate) particles, the otoliths, hence the name the otolith organ.

Action:

When the head is in normal erect position:

(1) The macula of each utricle is approximately in the horizontal plane, with the cupula, hair and otoliths rising vertically from the macular epithelium and (2) The macula in each saccule lies in the vertical plane, with the hair and oyoliths projecting horizontally sideways into cupula.

Functions: The otolith organ (saccule and utricle) of the vestibular apparatus (labyrinth) is stimulated by gravity and the semicircular canals are activated by rotational movements. It plays an important role in postural activity.

It gives rise to afferent impulse s which reflexly adapt the position of the trunk and limbs to that of the head. Thus enables the erect position of the head and the normal posture of the body to be maintained.

Information from the vestibular apparatus also reach cranial nerve nuclei (which supply the eye muscle) and the cerebral cortex. This helps the recognition of the position and movements of the head. As a result the position of the eyes is held approximately constant allowing visual fixation on moving objects.

II

(a) Myasthenia gravis:

Repeated refer Aug 2008, Feb 2009, Aug 2011

(b) Pacemaker potential:

Repeated refer: Aug 2008, 2009

(c) Maximum breathing capacity:

(d) Parkinson’s disease:

Repeated refer: Aug 2005, 07, 09

(e) ECG and causes for each wave:

Repeated refer: March 2002, Sept 2002

(f) Excitation secretion coupling:

Repeated refer :Feb 2007,Feb 2010

(g) Dark adaptation:

Repeated refer: Aug 2008, 11, Nov 2001

(h) Colour vision:

Repeated refer: Aug 2010, 11

(i) Basal ganglia:

Repeated refer: Nov 2001, Feb 2007 (j) Endorphins:

The gene that is transcribed to form the RNA molecule that causes ACTH synthesis initially causes the formation of a considerably larger protein, a preprohormone called proopiomelanocortin (POMC), which is the precursor of ACTH as well as several other peptides, including melanocyte stimulating hormone (MSH), β-lipotropin, β-endorphin, and a few others .

Under normal conditions, none of these hormones is secreted in enough quantity by the pituitary to have a significant effect on the human body, but when the rate of secretion of ACTH is high, as may occur in Addison’s disease, formation of some of the other POMC derived hormones may also be increased.

Paper IV Feb- 2005 Sub code – 4054

I) Essay:

1A. Cardiac Cycle:

The sequence of changes in the pressure and flow in the heart chamber and blood vessels in between the two subsequent cardiac contractions.

Pressure changes in left ventricle, atrium and aorta:

The a wave is caused by atrial contraction. Ordinarily, the right atrial pressure increases 4 to 6 mm Hg during atrial contraction, and the left atrial pressure increases about 7 to 8 mm Hg.

The c wave occurs when the ventricles begin to contract; it is caused partly by slight backflow of blood into the atria at the onset of ventricular contraction but mainly by bulging of the A-V valves backward toward the atria because of increasing pressure in the ventricles.

The v wave occurs toward the end of ventricular contraction; it results from slow flow of blood into the atria from the veins while the A-V valves are closed during ventricular contraction. Then, when ventricular contraction is over, the A-V valves open, allowing this stored atrial blood to flow rapidly into the ventricles and causing the v wave to disappear.

second heart sound:

When the aortic and pulmonary valves close at the end of systole, one hears a rapid snap because these valves close rapidly, and the surroundings vibrate for a short period. This sound is called the second heart sound.

2A. stretch reflex :

The simplest manifestation of muscle spindle function is the muscle stretch reflex. Whenever a muscle is stretched suddenly, excitation of the spindles causes reflex contraction of the large skeletal muscle fibers of the stretched muscle and also of closely allied synergistic muscles.

Stucture of muscle spindle:

Each spindle is 4 mm long. It is built around 3 to 12 very small intrafusal muscle fibers that are pointed at their ends and attached to the surrounding large extrafusal skeletal muscle fibers.

Each intrafusal muscle fiber is a very small skeletal muscle fiber. The central region of each of these fibers that is the area midway between its two ends has few or no actin and myosin filaments.

Motor Innervation of the Muscle Spindle:

The end portions that do contract are excited by small gamma motor nerve fibers that originate from small type A gamma motor neurons in the anterior horns of the spinal cord. These gamma motor nerve fibers are also called gamma efferent fibers, in contradistinction to the large alpha efferent fibers (type A alpha nerve fibers) that innervate the extrafusal skeletal muscle.

Sensory Innervation of the Muscle Spindle:

The receptor portion of the muscle spindle is its central portion. In this area, the intrafusal muscle fibers do not have myosin and actin contractile elements. They are stimulated by stretching of this midportion of the spindle.

Two types of sensory endings are found in this central receptor area of the muscle spindle. They are the primary ending and the secondary ending.

Functions of muscle spindle:

Muscle Spindle is the receptor of stretch reflexes which are fundamental reflexes to regulate posture.

1. By Length Servo Mechanism:

Muscle spindle compares the length of extrafusal fibers with intrafusal fibers and there by controls the length of extrafusal fibers.

2. By Follow up Servo Mechanism:

Muscle spindle also acts in regulation of posture by sustained contraction of muscle.

Reciprocal Inhibition:

when a stretch reflex excites one muscle, it often simultaneously inhibits the antagonist muscles.

This is the phenomenon of reciprocal inhibition, and the neuronal circuit that causes this reciprocal relation is called reciprocal innervation.

The pathway mediating this effect is bisynaptic, i.e., 2 synapses are involved.

II) Short Notes:

a) Regulation of coronary blood flow

Refer : March 2002, Aug 2008

b) Hypoxic hypoxia

Refer: Feb 2007, Aug 2007

c) Decompression sickness

Refer: Feb 2008, 2009

d) Definition and measurement of FRC

Refer: Aug 2008, March 2005

e) Role of hypothalamus on hunger perception

The area associated with hunger is the lateral hypothalamic area.

Damage to this area on both sides of the hypothalamus causes the animal to lose desire for food, sometimes causing lethal starvation causing anorexia.

Another area of the hypothalamus that enters into overall control of gastrointestinal activity is the mamillary bodies; these control at least partially the patterns of many feeding reflexes, such as licking the lips and swallowing.

f) Mechanism of accommodation for near vision

Sept 2002: Oct 2003

g) Structure and function of middle ear

Repeated refer: Oct 2003, Feb 2007

h) Taste pathway

Repeated refer: April 2001, March 2002

i) Chloride shift

Aug 2008, 09

j) Stages of asphyxia:

It is produced by occlusion of airways. This results in hypoxia and hypercapnia .

1) Initially there will be marked stimulation of respiration with violent respiratory efforts;

2) Blood pressure and heart rate increases

3) Blood pH falls

4) Increased catecholamine secretions

5) When CO2 increases above a certain level, it

-Depresses respiratory center and VMC

-Severe hypoxia also produces cardiac arrest

Paper IV Feb 2006 sub code: 4054

I) Essay

1A. Blood pressure;

Refer: Aug 2008, Oct 2003

2A. Cerebellum:

Refer: Feb 2008, 09

II) Short Notes

a) Spirogram A simple method for studying pulmonary ventilation is to record the volume movement of air into and out of the lungs, a process called spirometry. The record is said to be a spirogram, indicating changes in lung volume under different conditions of breathing.

They are:

1. The tidal volume.

2. The inspiratory reserve

3. The expiratory reserve

4. The residual volume

b) Dysbarism Refer: Feb 2005, 08, 09

c) Hypoxia Refer: Feb 2007, Aug 2007

d) Heart sounds

First Heart Sound: Produced by closure of the A-V valves during ventricular systole. The vibration is low in pitch and relatively long-lasting and is known as the first heart sound.

Second Heart Sound: Produced by closure of semi lunar valves at the end of systole, rapid snap because these valves close rapidly, and the surroundings vibrate for a short period.

Third Heart Sound: Occasionally a weak, rumbling third heart sound is heard at the beginning of the middle third of diastole.

Fourth Heart Sound: An atrial heart sound can sometimes be recorded in the phonocardiogram, but it can almost never be heard with a stethoscope because of its weakness and very low frequency.

e) Triple response Refer: Feb 2009, 2010

f) Berger’s rhythm  Also said to be as α rhythm  They are present at rest when the eyes are closed and form the most prominent component of the EEG.  Its frequency is 8-12 Hz  Amplitude is 50-100 µV  Present maximally in the occipital and Parieto-occipital areas when the eyes are closed.  The replacement of regular α rhythm with fast, high frequency, irregular low amplitude activity is called alpha-block.

g) Decerebrate rigidity

 Decerebrate posturing is also called decerebrate response, decerebrate rigidity, or extensor posturing.  It describes the involuntary extension of the upper extremities in response to external stimuli.  In decerebrate posturing, the head is arched back, the arms are extended by the sides, and the legs are extended.  A hallmark of decerebrate posturing is extended elbows. The arms and legs are extended and rotated internally.  The patient is rigid, with the teeth clenched. The signs can be on just one or the other side of the body or on both sides, and it may be just in the arms and may be intermittent.

h) Errors of refraction Refer: March 2002, Feb 2007

i) Aqueous humor Refer: Aug 2010

j) Cochlear micro phonic potential

 One of the electrical responses of the cochlea to sound is the cochlear micro phonic potentials.  It is a potential fluctuation that can be recorded between an active electrode placed on or near the cochlea and an indifferent electrode placed any where in the body.  It is called the micro phonic potential because if these potentials are amplified, the loudspeaker records the pure tone as sound waves upto frequencies of 20000 Hz.  These potentials are similar to generator potential  The Cochlear micro phonic potentials are produced by transformation of mechanical energy into electrical energy.  These potentials can be recorded by placing one electrode in the scala media and one in the scala tympani.  Thus these potentials are developed as a modification of the endolymphatic potential  Like the endolymphatic potential these potentials are also altered by movement of the basilar membrane and show linear relationship to the magnitude of the basilar membrane displacement.  The base of the cochlea responds to all frequencies of sound stimuli while the apex responds to only low frequencies of sound.

Paper IV Feb 2007 Sub code: 4054

I) Essay:

1) ECG from standard limb lead:

When the cardiac impulse passes through the heart, electrical current also spreads from the heart into the adjacent tissues surrounding the heart. A small portion of the current spreads all the way to the surface of the body. If electrodes are placed on the skin on opposite sides of the heart, electrical potentials generated by the current can be recorded; the recording is known as an electrocardiogram.

Characteristics of the Normal Electrocardiogram - The normal electrocardiogram is composed of a P wave, a QRS complex, and a T wave. - The QRS complex is often, but not always, three separate waves: the Q wave, the R wave, and the S wave. - The P wave is caused by electrical potentials generated when the atria depolarize before atrial contraction begins. - The QRS complex is caused by potentials generated when the ventricles depolarize before contraction, that is, as the depolarization wave spreads through the ventricles. - Therefore, both the P wave and the components of the QRS complex are depolarization waves. - The T wave is caused by potentials generated as the ventricles recover from the state of depolarization. - This process normally occurs in ventricular muscle 0.25 to 0.35 second after depolarization, and the T wave is known as a repolarization wave.

Voltage and Time Calibration of the Electrocardiogram

- The horizontal calibration lines are arranged so that 10 of the small line divisions upward or downward in the standard electrocardiogram represent 1 millivolt, with positivity in the upward direction and negativity in the downward direction. - The vertical lines on the electrocardiogram are time calibration lines. - Each inch in the horizontal direction is 1 second, and each inch is usually broken into five segments by dark vertical lines; the intervals between these dark lines represent 0.20 second. - The 0.20 second intervals are then broken into five smaller intervals by thin lines, each of which represents 0.04 second.

ECG changes in abnormal conditions:

Tachycardia – RR interval reduced. Right ventricular hypertrophy – right axis deviation Right BBB - right axis deviation Left ventricular hypertrophy - Left axis deviation. AV nodal delay – PR interval prolonged Myocardial infarction – inverted T wave.

2) Connections and functions of Basal Ganglia. Repeated refer:Aug 2005, nov 2001

3) Errors of refraction and correction. Repeated refer: March 2002, feb 2008

II) Short notes: a) Neural regulation of respiration. Repeated refer: Aug 2009 b) Hypoxia. Repeated refer: April 2001, aug 2007 c) Excitation contraction coupling. Repeated refer: Aug 2006 d) Functions of middle ear. Repeated refer: oct 2003, Feb 2005 e) Functions of parietal lobe.

(i) Post central gyrus: appreciation of elementary sensations of touch, pain, pressure and temperature. (ii) Superior parietal lobule: associated between discrimination of between stimuli. (iii) Inferior parietal lobule: Stereognosis, Spatial relationship, Two point discrimination. f) Functions of thalamus. Repeated refer: feb 2011

Paper – IV Aug 2007 sub code : 4054

1. Hypoxia:

Repeated refer: Feb 2007, April 2001

2. Visual pathway:

Repeated refer: Aug 2004, Aug 2008, 09

3. Short notes: a) korotkoff sounds:

Arterial pressure cycle, a sound then is heard with each pulsation. These sounds are called Korotkoff sounds.The exact cause of Korotkoff sounds is still debated, but they are believed to be caused mainly by blood jetting through the partly occluded vessel.

The jet causes turbulence in the vessel beyond the cuff, and this sets up the vibrations heard through the stethoscope.

In determining blood pressure by the auscultatory method, the pressure in the cuff is first elevated well above arterial systolic pressure. As long as this cuff pressure is higher than systolic pressure, the brachial artery remains collapsed so that no blood jets into the lower artery during any part of the pressure cycle.

Therefore, no Korotkoff sounds are heard in the lower artery. But then the cuff pressure gradually is reduced. Just as soon as the pressure in the cuff falls below systolic pressure, blood begins to slip through the artery beneath the cuff during the peak of systolic pressure, and one begins to hear tapping sounds from the ante cubital artery in synchrony with the heartbeat.

As soon as these sounds begin to be heard, the pressure level indicated by the manometer connected to the cuff is about equal to the systolic pressure. As the pressure in the cuff is lowered still still more, the Korotkoff sounds change in quality, having less of the tapping quality and more of a rhythmical and harsher quality.

Then, finally, when the pressure in the cuff falls to equal diastolic pressure, the artery no longer closes during diastole, which means that the basic factor causing the sounds (the jetting of blood through a squeezed artery) is no longer present.

Therefore, the sounds suddenly change to a muffled quality, then disappear entirely after another 5- to 10-millimeter drop in cuff pressure. One notes the manometer pressure when the Korotkoff sounds change to the muffled quality; this pressure is about equal to the diastolic pressure.

b) Heart sounds:

Repeated refer: Feb 2006

c) Timed vital capacity: Also called Forced Vital Capacity

 Exceedingly useful clinical pulmonary test, and one that is also simple, is to make a record on a spirometer is the forced expiratory vital capacity (FVC).  In performing the FVC maneuver, the person first inspires maximally to the total lung capacity, then exhales into the spirometer with maximum expiratory effort as rapidly and as completely as possible.  The difference between the two records

(1) For normal lungs and

(2) For partial airway obstruction.

The total volume changes of the FVCs are not greatly different, indicating only a moderate difference in basic lung volumes in the two persons. There is, however, a major difference in the amounts of air that these persons can expire each second, especially during the first second. Therefore, it is customary to compare the recorded forced expiratory volume during the first second (FEV1) with the normal. In the normal person the percentage of the FVC that is expired in the first second divided by the total FVC

(FEV1/FVC %) is 80 per cent. However, in airway obstruction, this value decreased to only 47 per cent. In serious airway obstruction, as often occurs in acute asthma, this can decrease to less than 20 per cent.

d) Oxygen dissociation curve

Repeated refer: e) Non respiratory functions of lung:

Repeated refer: f) ECG leads:

Repeated refer: March 2002, Sep 2002 g) Baro receptors:

Repeated refer: March 2002, Sep 2002 h) Color blindness:

Repeated refer: Sep 2012, Nov2011 i) Parkinsonism:

Repeated refer: Aug 2005 , Aug 2009 j) Middle ear:

Repeated refer: Oct 2003 , Feb 2005,07

Paper IV February 2008 Sub code: 4054

I) Essay:

1) Cerebellum. Repeated refer : feb 2006, feb 2009

2) Functions of hypothalamus.

1. Regulation of body temperature: Heat loss center and heat gain center plays a role in heat production and heat loss from the body.

2. Regulation of anterior pituitary gland. Regulates the activity of anterior pituitary by releasing and inhibiting hormones. eg. GHRH and GHIH

3. Regulation of posterior pituitary gland. In formation of posterior pituitary hormones like ADH and oxytocin.

4. Control of Circardian rhythm. It controls the diurnal variation of body functions for every 24 hrs like sleep wake cycle, melatonin cycle etc. Mechanism – receives inputs via Retinohypothalamic tract and LGB.

5. Control of ANS. It is called the head ganglion for ANS. Lateral area of hypothalamus – sympathetic responses Mid dorsal hypothalamus – sympathetic cholinergic responses

6. Control of hunger and feeding. It maintains the balance between caloric intake and expenditure. Satiety Center – ventromedial nuclei Feeding center – Lateral hypothalamic nuclei.

7. Role in water intake. Thirst sensation is aroused by dryness of the mouth because of decrease in ECFV or change in osmolality. This is sensed by osmoreceptors and stimulate the secretion of ADH and also directly stimulate the thirst center to increase the water intake.

8. Role in emotional behaviour. All emotional aspects like laughing, crying or blushing are acquired by integrated action of ANS and somatic efferent system.

9. Integrated control of the CVS. Major relay station of the corticohypothalamic descending pathway which discharge by emotions.

3) Short notes on: a) Travelling wave theory. Repeated refer Nov 2001 b) Electroencephalogram. - The record of electrical activity of brain is known as EEG. - It is recorded by using cathode ray oscilloscope. - Normal EEG: a. Bipolar method b. Unipolar method

EEG Frequency Amplitude(mV) Associated features (Hz) Alpha wave 8-12 50-100 Occipital area when eyes are closed Beta wave 14-30 5-10 Frontal area in infants Theta wave 4-7 10 Early in sleep Delta wave 1-4 20-200 Usually during sleep

Physiology of EEG: - Activity recorded due to rhythmical discharge of cell bodies in the most superficial layers of cortical grey matter. c) Reynold’s number: Repeated refer: Aug 2006 d) Plastictiy of smooth muscle:

- The relationship between initial length of muscle fiber and tension is called plasticity. - Force of contraction of a muscle fiber is directly proportional to initial length of muscle fiber under physiological limits. - It can exert variability of the tension at given length. - If a piece of visceral muscle is stretched it first exerts increased tension. - However, if the muscle is held at the greater length after stretching, the tension gradually decreases. - Therefore it is not possible to correlate the length and developed tension accurately and no resting length can be assigned. e) Decompression sickness Repeated refer: Feb 2005, 2009 f) Brown sequard syndrome. Repeeated refer: AUG 2008,09,11 g) Conditioned reflex.

- The ability to alter behaviour on the basis of experience is called learning. - Conditioned reflexes are important type of learning. - These are acquired reflexes. - It is a reflex response to stimulus that did not previously produce the response. - Later they produce response by pairing the stimulus with normal stimulus that will normally produce response. - Eg. Pavlov‘s classical dog experiment - Mechanism: Habituation and sensitization are the basis of conditioned reflexes Reinforcement is essential for conditioned reflexes. h) Heart failure.

- Failure of heart to maintain an adequate cardiac output for normal perfusion throughout the body. - Pathogenesis o Systolic and diastolic heart failure - Causes: o Myocardial infarction o Congestive heart failure o Arrythmia - Clinical manifestations o Forward and backward failure . dyspnoea . Orthopnoea . generalised weakness - Copensatory mechanism o Frank starling‘s mechanism o Baroreceptor mechanism o Renal mechanism i) Refractory errors. Repeated refer: march 2002, feb 2007 j) Difference between three types of muscle

Skeletal muscle Cardiac muscle Smooth muscle 1. Location Most are attached to In heart only In viscera skeleton 2. Structure Striated muscle Cross striations and Plain muscle functional syncytium Single unit and multi unit 3. Control Voluntary control Involuntary Involuntary Well developed Neuromuscular Varicosities and neuromuscular junction beads junction Calcium binding Troponin C Troponin C Calmodulin protein RMP - 70 mV - 90 mV - 55 mV -

Paper IV August 2008 Sub Code: 4054

I) Essay:

1. Descending tracts of spinal cord. Pyramidal tracts – functions and effects of lesions at various levels.

Descending tracts: Pyramidal tract: Corticospinal tract Extrapyramidal tracts: Vestibulospinal tract Tectospinal tract Reticulospinal tract Rubrospinal tract Olivospinal tract Cortico spinal tract:

- These fibers originate from giant pyramidal cells, called Betz cells - The most important output pathway from the motor cortex is the corticospinal tract, also called the pyramida ltract - After leaving the cortex, it passes through the posteriorlimb of the internal capsule (between the caudate nucleus and the putamen of the basal ganglia) and then downward through the brain stem, forming the pyramids of the medulla - The majority 80% of the pyramidal fibers then cross in the lower medulla to the opposite side and descend into the lateral corticospinal tracts of the cord, finally terminating principally on the interneurons in the intermediate regions of the cord gray matter. - A few 20% of the fibers do not cross to the opposite side in the medulla but pass ipsilaterally down the cord in the ventral corticospinal tracts. - Then they synapse on anterior horn cells of the spinal cord at various levels and from there the motor nerve arises.

Functions of Corticospinal tract: - Lateral Corticospinal tract Control of fine voluntary movements - Ventral Corticospinal tract is involved in control muscles of trunk and proximal group of muscles.

Leisons of Corticospinal tract:

- At cortex: there will be UMN type spastic paralysis of affected area - At the level of internal capsule: Contralateral hemiplegia and facial palsy - At the midbrain level: Contralateral hemiplegia - Below alpha motor neuron level: Flaccid paralysis.

II) Short Notes:

1. Surfactanat:

- Surfactant is asurface active agent in water, which means that it greatly reduces the surface tension of water. - It is secreted by special surfactant-secreting epithelial cells called type II alveolar epithelial cells. - Surfactant is a complex mixture of several phospholipids, proteins, and ions. - The most important components are the phospholipid dipalmitoylphosphatidylcholine, surfactant apoproteins, and calcium ions. - The dipalmitoylphosphatidylcholine, along with several less important phospholipids, is responsible for reducing the surface tension. - Instead, part of the molecule dissolves, while the remainder spreads over the surface of the water in the alveoli. - This surface has from one twelfth to one half the surface tension of a pure water surface

2. Chloride shift:

Transport of CO2 in blood:

Inside RBC CO2 combines with H2O to form H2CO3

Dissociation of Carbonic Acid into Bicarbonate and Hydrogen Ions.

- The carbonic acid formed in the red cells (H2CO3) dissociates into hydrogen and bicarbonate ions (H+ and HCO3–). - Most of the hydrogen ions then combine with the hemoglobin in the red blood cells, because the hemoglobin protein is a powerful acid-base buffer. - In turn, many of the bicarbonate ions diffuse from the red cells into the plasma, while chloride ions diffuse into the red cells to take their place. - This is made possible by the presence of a special bicarbonate-chloride carrier protein in the red cell membrane that shuttles these two ions in opposite directions at rapid velocities. - Thus, the chloride content of venous red blood cells is greater than that of arterial red cells, a phenomenon called the chloride shift.

3. Artificial respiration: Repeated refer : Aug 2004, 11

4. Taste pathway: Repeated refer: April 2001, March 2002

5. Effect of lesion in optic pathway: Repeated refer: Aug 2004, 08 6. Brown Sequard syndrome. Repeated refer: Aug 2009, 11

7. Function of thalamus. Repeated refer: Aug 2001, Feb 2011

8. Pacemaker potential. Repeated refer: Aug 2009

9. Regulation of coronary circulation. Repeated refer: March 2002, Feb 11

10. Neuromuscular Junction:

- The skeletal muscle fibers are innervated by large, myelinated nerve fibers that originate from large motoneurons in the anterior horns of the spinal cord. - Each nerve ending makes a junction, called the neuromuscular junction, with the muscle fiber near its midpoint. - The nerve fiber forms a complex of branching nerve terminals that invaginate into the surface of the muscle fiber but lie outside the muscle fiber plasma membrane. - The entire structure is called the motor end plate. - The invaginated membrane is called the synaptic gutter or synaptic trough, and the space between the terminal and the fiber membrane is called the synaptic space or synaptic cleft. - In the axon terminal are many mitochondria that supply adenosine triphosphate (ATP), the energy source that is used for synthesis of an excitatory transmitter acetylcholine. - When a nerve impulse reaches the neuromuscular junction, about 125 vesicles of acetylcholine are released from the terminals into the synaptic space.

III) Short answer questions:

3) Windkessel effect.

During diastole The stretched elastic walls of aorta recoils and the potential energy stored is released into blood and causes the blood to flow during the diastole also. This effect responsible for continous blood flow is called Windkessel effect.

4) Phonocardiogram.

A microphone specially designed to detect low-frequency sound is placed on the chest, the heart sounds can be amplified and recorded by a high-speed recording apparatus. The recording is called a phonocardiogram.

5) Haldane’s effect.

Binding of oxygen with hemoglobin tends to displace carbon dioxide from the blood. Indeed, this effect, called the Haldane effect. If the carbon dioxide dissociation curve did not shift because of the Haldane effect, the carbon dioxide content of the blood would fall only to 50 volumes per cent, which would be a loss of only 2 volumes per cent of carbon dioxide. Thus the Haldane effect approximately doubles the amount of carbon dioxide released from the blood in the lungs and approximately doubles the pickup of carbon dioxide in the tissues.

6) VO2 max.

The level of oxygen consumed beyond which no further increase in O2 consumption occurs with further increase in severity of exercise. Average VO2 max in adults is 3 L/min and in trained athlete is 5L/min.

7) Babinski’s sign.

Stroking the sole of foot starting from lateral aspect of heel along the lateral border of the foot then below the toes and ending beneath the little toe. Babinski‘s sign positive or extensor plantar response is fanning out of toes and dorsiflexion of great toe along with plantar flexion at ankle joint. This occurs in UMN lesion, children and in deep sleep.

8) Alpha block.

Alpha block or alpha attenuation refers to a phenomenon in which alpha waves attenuatea and are replaced by the fast, irregular waves of low amplitude. It occurs during conscious mental activity.

9) Functions of aqueous humour.

(1) maintains intraocular pressure of eyeball. (2) metabolic role by providing substrates (3) removing the metabolites from the avascular cornea and lens.

10) Rinne’s test.

Placing the tapped tuning fork in mastoid process of subject after the vibration subsides place the blades of vibrating tunning fork along the pinna of ear after it subsides compare to examiners ear. If, AC > BC it is called Rinne‘s test positive.

Paper IV February 2009 Sub code: 4054

I) Essay

1. Cerebellum Repeated refer: Feb 2006, 08

2. Cardiac cycle Repeated refer: Aug 2006, Feb 2005

II) Short notes:

1. Neuromuscular junction. Repeated refer: Aug 2008

2. Compare REM and non REM sleep Repeated refer:

3. Triple response. Repeated refer: Feb 2006, Feb 2010

4. Formation, functions and circulation of CSF Repeated refer: April 01, Feb 10

5. Functions of vestibular apparatus.

- Semicircular canals – Stimulated by rotational movements - Saccule and utricle – stimulated by gravity and forward, backward acceleration. - It maintains the position of trunk and limbs to that of the head. - Helps in recongnizing the position of head and movements of head through cranial nerve nuclei. - For positioning the eye and fixing it to moving object. - Plays a role in regulation of posture and equllibrium - Orientation of body in space.

6. Dark adaptation. Repeated refer: Aug 2008, Nov 2001

7. Organ of corti. Repeated refer: March 2002

8. Decompression sickness. Repeated refer: Feb 2005, 08

9. Chemical control of respiration. Repeated refer: Nov 2001, Aug 2005

10. Myasthenia gravis. Repeated refer: Paper III Feb 2005

III. Short answer questions.

1. Astigmatism. Repeated refer: Feb 07, 08

2. Arterial pulse. Repeated refer: Feb 2010

3. Taste pathway. Repeated refer: April 01, March 02, Feb 05, 11, Aug 11

4. Rigor mortis.

- Several hours after death, all the muscles of the body go into a state of contracture called ―rigor mortis‖; that is, the muscles contract and become rigid, even without action potentials. - This rigidity results from loss of all the ATP, which is required to cause separation of the crossbridges from the actin filaments during the relaxation process. - The muscles remain in rigor until the muscle proteins deteriorate about 15 to 25 hours later, which presumably results from autolysis caused by enzymes released from lysosomes

5. Phantom limb.

- The patient usually experiences intolerable pain and proprioceptive sensations in the limb that is no longer present and this is called phantom limb.

6. Oxygen dept.

- During recovery phase of the exercise the extra amount of oxygen form because of ATP primarily produced by anaerobic mechanisms.

7. Bohr’s effect.

- When pCO2 is more in ECF or increased pO2 in blood there will be shift of oxygen dissociation curve to the right causing release of O2 into the tissues this effect is called Bohr‘s effect.

8. ECG. Repeated refer: March 2002, Sept 2002

9. Refractory period.

- A brief period during which a second successive stimulus will not prove any response in the muscle. o Absolute refractory period – maximal stimulus also will not provoke response o Relative refractory period – maximal stimulus will provoke little response.

10. Chronaxie, Rheobase and Utilization time Repeated refer Aug 2009

Paper IV August 2009 Sub code: 4054

I) Essay:

1) Ascending tracts and pain pathway Refer:

2) Neural regulation of respiration.

The nervous system normally adjusts the rate of alveolar ventilation almost exactly to the demands of the body so that the oxygen pressure (Po2) and carbon dioxide pressure (Pco2) in the arterial blood.

Respiratory Center

The respiratory center is composed of several groups of neurons located bilaterally in the medulla oblongata and pons of the brain stem. It is divided into three major collections of neurons: (1) a dorsal respiratory group, located in the dorsal portion of the medulla, which mainly causes inspiration; (2) a ventral respiratory group, located in the ventrolateral part of the medulla, which mainly causes expiration; and (3) the pneumotaxic center, located dorsally in the superior portion of the pons, which mainly controls rate and depth of breathing.

Dorsal Respiratory Group of Neurons—Its Control of Inspiration and of Respiratory Rhythm The dorsal respiratory group of neurons extends most of the length of the medulla. Most of its neurons are located within the nucleus of the tractus solitaries

Rhythmical Inspiratory Discharges from the Dorsal Respiratory Group. The basic rhythm of respiration is generated mainly in the dorsal respiratory group of neurons. This group of neurons still emits repetitive bursts of inspiratory neuronal action potentials.

Inspiratory ―Ramp‖ Signal. The nervous signal that is transmitted to the inspiratory muscles, mainly the diaphragm, is not an instantaneous burst of action potentials.

There are two qualities of the inspiratory ramp that are controlled, as follows: 1. Control of the rate of increase of the ramp signal 2. Control of the limiting point at which the ramp suddenly ceases

A Pneumotaxic Center A pneumotaxic center, located dorsally in the nucleus parabrachialis of the upper pons, transmits signals to the inspiratory area. The primary effect of this center is to control the ―switch-off‖ point of the inspiratory ramp, thus controlling the duration of the filling phase of the lung cycle.

Ventral Respiratory Group of Neurons Located in each side of the medulla, about 5 millimeters anterior and lateral to the dorsal respiratory group of neurons, is the ventral respiratory group of neurons, found in the nucleus ambiguus rostrally and the nucleus retroambiguus caudally. The neurons of the ventral respiratory group remain almost totally inactive during normal quiet respiration.

Afferent impulses to Respiratory centers: - Cerebral cortex - Limbic system - Pulmonary stretch receptors - Hering breuer reflex - J Receptors - Proprioceptors - Baroreceptors.

Periodic breathing:

Abnormality of respiration called periodic breathing occurs in a number of disease conditions. (i) Chyne stoke‘s breathing is characterized by slowly waxing and waning respiration occurring (ii) Biot‘s breathing.

II) Short Notes:

1. Compliance of lungs.

The extent to which the lungs will expand for each unit increase in transpulmonary pressure is called the lung compliance.

The total compliance of both lungs together in the normal adult human being averages about 200 milliliters of air per centimeter of water transpulmonary pressure. That is, every time the transpulmonary pressure increases 1 centimeter of water, the lung volume, after 10 to 20 seconds, will expand 200 milliliters. The two curves are called, respectively, the inspiratory compliance curve and the expiratory compliance curve, and the entire diagram is called the compliance diagram of the lungs The characteristics of the compliance diagram are determined by the elastic forces of the lungs. These can be divided into two parts: (1) elastic forces of the lung tissue itself and (2) elastic forces caused by surface tension of the fluid that lines the inside walls of the alveoli and other lung air spaces.

2. Brown sequard syndrome. Refer:

3. Blood Brain barrier.

- Blood brain barrier is made of foot process of astrocytes enclosing the blood vessels and tight endothelium of the capillaries. - The concentrations of several important constituents of cerebrospinal fluid are not the same as in extracellular fluid elsewhere in the body. - Furthermore, many large molecular substances hardly pass at all from the blood into the cerebrospinal fluid or into the interstitial fluids of the brain even though these same substances pass readily into the usual interstitial fluids of the body. - Therefore, it is said that barriers, called the blood–cerebrospinal fluid barrier and the blood-brain barrier, exist between the blood and the cerebrospinal fluid and brain fluid, respectively. - Barriers exist both at the choroid plexus and at the tissue capillary membranes in essentially all areas of the brain parenchyma except in some areas of the hypothalamus,pineal gland, and area postrema, where substances diffuse with greater ease into the tissue spaces. - The ease of diffusion in these areas is important because they have sensory receptors that respond to specific changes in the body fluids, such as changes in osmolality and in glucose concentration. Functions: - Protects the sensitivity of cortical neurons - Protects the brain from exogenous and endogenous toxins - Prevents the escape of neurotransmitters into general circulation.

4. Surfactant Refer: august 2008

5. Chronaxie and Rheobase.

The relationship between strength of stimulating current and the duration it must be applied to produce a response called Strenght duration curve.

Rheobase: The weakest current strength which can excite a tissue if allowed to flow through it for adequate duration of time.

Chronaxie: The length of time for which a current of twice a rheobase intensity must be applied to produce a response is called chronaxie.

6. Pupillary light reflexes.

- When light is shone into the eyes, the pupils constrict, a reaction called the pupillary light reflex. - The neuronal pathway for this reflex is demonstrated by the upper two black traces . - When light impinges on the retina, a few of the resulting impulses pass from the optic nerves to the pretectal nuclei. - From here, secondary impulses pass to the Edinger-Westphal nucleus and, finally, back through parasympathetic nerves to constrict the sphincter of the iris. - Conversely, in darkness, the reflex becomes inhibited, which results in dilation of the pupil. - The function of the light reflex is to help the eye adapt extremely rapidly to changing light conditions.

7. Pacemaker potentials. Refer: Aug 2008

8. Atrial natriuretic peptide.

- Group of polypeptides produced by atrial muscle cells that increases the urinary excretion of sodium. - ANP is secreted when NaCl intake is increased or increase in ECFV. - Increase ECFV stimulates atrial stretch receptors in the right atrium - Release of ANP. Efferent arteriolar constriction----Increased GFR------Natriuresis Afferent arteriolar relaxation Decreases aldosterone ------Natriuresis.

9. Optic pathway Refer: Aug 2004, feb 2011

10. Peculiarities of pulmonary circulation.

- Pulmonary artery is 5 cm long and divides into right and left pulmonary artery. - Pulmonary arterioles is divided into network of capillaries. - Network of pulmonary capillaries surrounds the alveoli and increase the surface area for diffusion of gases. - Pulmonary venules and veins receives oxygenated blood from the capillaries. - At rest 1L of blood is present in thorax. - Pulmonary system is a low pressure system it is much less than the systemic arterial pressure. Mean pulmonary arterial pressure is 10 – 15 mm Hg - Pulmonary capillary flow at rest is pulsatile in nature. - Pulmonary vascular reflexes – Baroreceptor reflexes, Bain bridge reflex.

III) Short answer questions:

1) Wernicke’s aphasia.

- It is also known as sensory aphasia or fluent aphasia. - Patient talks excessively with no sense. - Patient can understand the meaning of spoken or written words.

2) Acetylcholine.

- Ach is synthesised in mitochondria from choline in presence of acetylcholine esterase. - It is a excitatory neurotransmitters released from the cholinergic nerve endings. - It has two types of receptors muscuranic and nicotinic.

3) Parkinsonism features.

- Loss of associated movements. - Static tremor. - Festinant gait. - Rigidity. - Expressionless face.

4) REM sleep.

- EEG shows desynchronized pattern - Characterised by burst of saccadic eye movements. - Skeletal muscle tone reduced. - Dreaming is associated with this sleep.

5) Anti – G suit.

- Specific procedures and apparatus have been developed to protect aviators against the circulatory collapse that might occur during positive G. - Special ―anti-G‖ suits have been devised to prevent pooling of blood in the lower abdomen and legs. - The simplest of these applies positive pressure to the legs and abdomen by inflating compression bags as the G increases.

6) Clinical significance of EEG.

- Localisation of pathological conditions like sub dural hematoma. - Diagnosis of epilepsy. Grandmal epilepsy Petitmal epilepsy Psychomotor epilepsy.

7) Chloride shift: Repeated; refer; feb 2005, august 2008

8) Jugular venous pulse. Repeated refer : feb 2009

9) Contents of middle ear.

- Bones: Malleus, Incus and Stapes

- Muscles: Stapedius and tensor tymphani.

10) Functions of placenta.

- Hormonal synthesis – HCG,HCS,HCT and progesterone, oestrogen - Placenta for the foetus combines the work of alimentary tract, kidneys and lungs. - It supplies maternal blood flow to the foetus. - Placenta is responsible for gaseous transport and exchange to the foetus.

Paper IV February 2010 Sub code: 4054

I) Essay

1) Types of muscular exercise and physiological changes during and after exercise:

Classification : a) Based on Oxygen requirement:

- Aerobic exercise eg. jogging - Aneorobic exercise eg. weight lifting b) Based on severity of exercises (MET‘s)

- Mild exercise less < 3 MET‘s - Moderate exercise 3 – 4.5 MET‘s - Severe exercise 4.5 – 7 MET‘s - Very heavy exercise > 7 MET‘s

Cardiovascular changes to exercise:

(i) Heart rate: During exercise max HR attained can be 220 – age.

Due to - neurogenic – psychic stimuli - peripheral feedback - chemical changes

(ii) Stroke volume:

Increases to twice during exercise.

(iii) Cardiac output:

Increases to 5 – 6 times Due to increase in SV and HR.

(iv) Blood pressure:

Systolic BP increases with exercise Diastolic BP no change with mild and moderate exercise

(v) Blood volume:

Decreases by 15% due to hemoconcentration.

Respiratory changes to exercise:

(i) Pulmonary ventilation: (PV)

- During moderate exercise it increases to 15 – 18 times ie) 70 – 80 lit/min. - PV increases in parallel with the increase in O2 consumption (VO2 max). Mechanism: - Psychic stimulus - Afferent stimuli from propriceptors - Stimulation of carotid bodies - Accumulation of lactic acids

(ii) Pulmonary diffusion of O2:

- Increased by 3 times: o Increased blood perfusion o Opening of more capillaries.

(iii) oxygen consumption:

- Increases by 12 – 15 times o Increase in cardiac output o Increase in alveolar ventilation o Increase in capillary density.

2. How low pressure vibrations in the air are perceived as sound:

Role of middle ear: - Pinna collects the sound waves and to localize the sounds. - helps in transmitting the sound waves into tymphanic membrane.

Role of middle ear:

(i) Tymphanic membrane - Sound receiver - resonator.

(ii) Ear ossicles: - It acts as a level system - Impedence matching o Size of handle of malleus is less than incus o surface area of tymphanic membrane larger than stapes foot process

(iii) Tymphanic or attenuation reflex

Role of inner ear

Vibration of basilar membrane

movement of foot plate

vibration set up in perilymph

Basilar membrane dipped into Scala tymphani

basilar and tectorial membrane attached to limbus

So when the basilar membrane moves it disturbs the tectorial membrane and it bends the hair cells

action potential in auditory nerve

Mechanism of pitch determination: - Place theory / van Bekesy travelling place wave theory

- Volley principle

II) 1. Kirchoff’s law and Einthoven’s law

Kirchoff‘s law:

It states that in a closed circuit sum of current flow is equal to zero. ie) i1 + i2 + i3 – i4 = 0

In ECG,

lead I – lead II + lead III = 0

lead II = lead I + lead III

Einthoven‘s law:

At any given instant (movement) the sum of the potential in lead I and lead II equals the potential in lead II ie) lead II = lead I + lead III

2. Excitation contraction coupling in cardiac muscle:

- Cardiac muscle fiber is excitable - The duration of action potential is 250 msec

Phase: 0 from RMP of – 90 mV rapid depolarisation to + 20 mV to + 35 mV

Phase : 1 after rapid fall (depolarisation )

Phase : 2 steady plateau phase due to influx of Ca+ ions which compensate for the K + efflux.

Phase : 3 after closure of Ca+ channels, K+ efflux causes re-polarisation

This action potential spread along the T tubules of sacroplasmic reticulum and takes the impulse into cardiac muscle fiber.

- large amount of Ca+ enters from ECF - Ca+ ions initiate the contraction process. - they bind with troponin C - this exposes the active sites of actin by moving the tropomyosin - myosin head binds and power stroke causes contraction

Cardiac muscle acts as a syncitium and all fibers contract together.

3. Triple Response:

Skin scratched with a partially pointed edge.

- produces 3 response - Postulated by Lewis 1927

(i) Red reaction or red line: - reddening at the site - approx appears by 10 min - Chemically mediated by release of histamine and bradykinin

(ii) Flare: - Dialation of arterioles - erythematous area spreads out - mediated by axon reflex – antodromic conduction

(iii) Wheal: - blister like appearance and edematous swelling - Due to release of histamine and other chemicals.

4. Physiological dead space:

Volume of air in anatomical dead space plus the volume of air in alveoli that does not involve in gaseous exchange.

- alveoli when no pulmonary blood flow - alveoli over ventilated

Clinically anatomical and physiological dead space are the same.

Measurement: By bohr‘s equation:

Dead space volume = Expired air volume x (pCO2 alveolar – pCO2 in expired air)

pCO2 in alveolar

5. Dysbarism

Refer: Feb 2005, 08

6. Causes of muscle tone:

- it depends upon the strech reflex - muscle spindles innervated by gamma motor neurons are responsible. - Gamma motor neuron is controlled by higher centers

Facilitatory centers: - facilitatory reticular formation - vestibular apparatus

Inhibitory centers: - Basal ganglia - Inhibitory reticular formation - Cerebellum.

7. Functions of paleostriatum;

Refer: Nov 2001, Aug 2005

8. Climbing , Mossy and parallel fibers

Cerebellum has 3 layers: - Outer molecular layer, - Middle purkinje cell layer and - Inner granule cell layer.

a) Climbing fibers:

the afferent fibers from inferior olivary nucleus ascend as climbing fibers and form synapses with denrites purkinje cells. b) Parallel fibers:

Basket cells posses a sparse dentritic tree which receives input from parallel fibers. Each cell axon ascends to the outer molecular layer and bifurcates to form T and are called parallel fibers. c) Mossy fibers:

These are axons of spinocerebellar, vestibulocerebellar and cortico ponto cerebellar tracts.

9. Control of appetite:

- It is determined by balance between caloric intake and energy expenditure. - Two hypothalamic centers concerned with hunger and feeding: o Satiety center – ventero medial nuclei o Feeding center – lateral hypothalamic area

Mechanism:

Satiety center is the primary center that controls the food intake.

Glucostats:

The cells of venteromedial nuclei act as satiety center due to they function as gluco receptors.

Inhibited by (-) Facilitated by (+)

- Increased blood glucose level - increased palatability - Increased plasma food intake - exercise - Fever - cold environment - hunger contractions

10. Induction of sleep.

Genesis of NREM (or slow wave sleep):

- Inhibitoin of RAS inputs by the descending pathways arising from the pre-optic area and diagonal band of broca. - Stimulation of sleep promoting mechanism o Diancephalic sleep zone o Medullary synchronizing zone

Genesis of REM sleep:

- discharge of nor-epinephrine from pontine reticular formation - PGO spikes are due to discharge of cholinergic neurons.

III) 1. Tracing of arterial pulse:

Two limbs

- Anacrotic limb (upstroke) – due to systole of heart (ejection phase) - Catacrotic limb (downstroke) – relaxation diastole of heart

Dicrotic notch

- closure of semilinar valves and rebound of blood into aorta.

2. Reynold’s number:

Refer: Feb 2002

3. Pre load and after load of heart:

Pre – load: Load acting on heart befor onset of contraction Eg: end diastolic volume

Aftre load: Load against which heart has to pump the blood. Eg. Peripheral resistance

4. Sneezing reflex: - protective reflex - stimulation of nasal mucosa, nasopharynx - Stimulates respiratory neurons

Response: Forcefull expiratory effort with closure of glottis

5. Denervation hypersensitivity:

When motor nerves to skeletal muscle is cut and allowed to degenerate the muscle gradually becomes extremely sensitive to ‗Ach‘

Reason: Reduction in neurotransmitters causes increase in active receptors

6. Reciprocal inhibition: In a stretch reflex, activity in the afferent fibers from the muscle spindles excites the motor neurons supplying the muscles from which the impulses come and inhibits the group of antagonists.

7. Consolidation of memory:

- Consolidation or encoding process involves hippocampus and neighbouring cortex viz. entorrhinal, perihinnal and parahippocampal areas. - Connections are formed containing cell bodies and fibers of cholinergic system. - Protein synthesis and activation of genes are involved in memory process.

8. Formation of CSF: - 50% from chroid plexus in ventricles. - 40 % from blood vessels of meningeal and ependymal lining of ventricles. - 10 % by blood vessels of brain an dspinal cord.

9. Gustatory receptors:

- They are chemoreceptos - They are 3 types of papillae o Fungiform papillae o Filliform papillae o Circumvallate papillae o Foliate papillae

10. Dark adaptation:

Refer : Aug 2008

Paper IV August 2010 Sub code: 4054

I)

1. Short term and long term regulation of arterial blood pressure.

Repeated refer: March 2002 & Sept 2002

2. Auditory pathway and conductive deafness:

The ear converts the sound waves in the external environment into action potentials in the auditory (VIII) nerve

The sound waves are changed greatly by the tympanic membrane and ear ossicles into movements of the foot plate of the stapes. These movements set up waves in the fluid present in the inner ear.

The action of waves in the organ of corti (hair cells) generates action potentials in the nerve fibers.

1. The axons of the spiral ganglion that innervate the hair cells form the cochlear (auditory) division of VIII nerve. The auditory nerve enters the medulla and ends in ventral and dorsal cochlear nuclei, the site of first synapse. 2. Second order neurons form the cochlear nuclei end in superior olive and trapezoid body on both sides of the brain stem from where third order neurons take origin. 3. Third order neurons pass up via variety of pathways in the lateral lemniscus to the inferior colliculi of both sides. Some of these fibers also send collaterals to the reticular formation and medial geniculate bodies in the thalamus. 4. From the inferior colliculi many fibers project and relay in the medial geniculate bodies ; medial geniculate bodie neurons finally project to the primary auditory cortex (area 41).Nerve impulses are perceived as sound 5. Auditory association areas : area22,21 and20 Area 22: Wernicke’s area concerned with the processing of auditory signals related to speech (spoken or written). Area 21 and20 concerned with interpretation and integration of auditory impulses. Lesions of these areas impair auditory short term memory without impairing visual memory.

Conductive deafness:

It is due to sound transmission defect either in the external or middle ear. Therefore, it is characterized by partial loss of hearing. The hearing loss is fairly uniform throughout the frequency range but it is never complete. It is because of skull bones themselves conduct sound to the cochlea (bone conduction) and the basilar membrane can be set into vibration. Causes:

(i) Wax or foreign bodies in the external ear (ii) Thickening of the tympanic membrane due to repeated infections, therefore, its vibrations decrease. (iii) Otitis media i.e. middle ear inflammatory disorders which damage the tympanic membrane and/ or the ear ossicles. (iv) Otosclerosis (ear ossicles sclerosis) i.e. pathological fixation of footplate of stapes in the oval window. (v) Blockage of the Eustachian tube.

II)

1. Theories of Hearing Repeated refer: Nov 2001 , Feb 2008,12 2. Anterior Spino thalamic tract: Also called as ventral spinothalamic tract,

Origin: from the axons of1 st order neurons in the posterior root ganglia.

Situation, extent and termination:

(i) After entering the spinal cord the fibers end round the cells which are situated at the median part in the dorsal horn( 1 st relay station), from where 2 nd order neuron arises. (ii) Most of the 2 nd order neurons cross in anterior commissure obliquely to opposite side of the same segment, and ascend in anterior column of spinal cord to end in the ventoposterior nucleus of thalamus. (iii) While ascending upwards anterior spinothalamic tract runs in parallel with the lateral spinothalamic tract and together they constitute the spinal lemniscus or anterolateral system of ascending fibers. (iv) In thalamus, 3 rd order neuron starts and axons of this neuron via posterior limb of internal capsule end in the sensory cortex (postcentral gyrus i.e. area 3, 1, 2). (v) The sensory pathways from somatic receptors on the left side of the body go to the somatosensory cortex on the right cerebral hemisphere, and vicevrersa.

Function- it conveys:

Crude touch sensations i.e. touch with high threshold.

3. Postural reflexes:

Definition: The muscles that maintain comfortable upright posture i.e. support the body’s weight against gravity. It is controlled by the brain and by reflex mechanisms that are passed into the neural networks of the brainstem and spinal cord. They are concerned with maintaining upright static posture and that of maintaining balance.

The maintenance of posture and balance is accomplished by means of complex interacting postural reflexes. It has 3 major components:

(i) The afferent pathways of the reflex arc come from the eyes, the vestibular apparatus and the proprioceptors. (ii) The efferent pathways are the α- motor neurons to the skeletal muscles; and (iii) The integrating centers are neuronal networks in the brainstem and spinal cord.

The postural reflexes not only maintain the body in an upright balanced position but also provide the constant adjustments necessary to maintain a stable possible background for voluntary activity.

These adjustments include:

(i) Static reflexes which involve sustained contraction of the musculature; and (ii) Phasic reflexes which involve transient movements.

A major factor in control of posture is variation in the threshold of the spinal stretch reflexes. This in turn caused by:

I. Changes in the excitability of the motor neurons; and II. Changes in the rate of discharge in the γ – motor neurons to muscle spindles.

The postural reflexes are integrated at various levels in the spinal cord to the cerebral cortex.

Ex… medulla, midbrain, thalamus, hypothalamus etc…

The part played by different regions of the nervous system in the regulation of posture can be obtained by a study of animals in which parts of neural axis has been removed.

4. Aqueous humor: Repeated refer: Feb 2006 5. Taste pathway: Repeated refer: March 2002, Feb 2005, Aug 2008 6. Cerebral circulation: Repeated refer: Sep 2002 7. Color vision: Repeated refer: Aug 2011

8. Carbon dioxide transport

Tissue activity produces CO2 which enters the blood due to:

(1) Difference in p CO2 between arterial blood and tissues. Arterial blood p CO2 is 40 mm Hg and tissue pCo2 is 46 mm Hg.

(2) CO2 has high diffusion coefficient, 20 times more than that of O2; therefore, even this small

pressure gradient of 6 mm Hg is sufficient for CO2 transport.

(3) Decrease in O2 content, shifts “CO2 dissociation” curve to left, causing further loading of CO2 from the tissues to the blood.

Transport of blood in the blood

(1) CO2 content of arterial blood is 48 ml % and that of venous blood is 52 ml%. Therefore, each 100

ml of arterial blood which passes through tissues picks up 4 ml of CO2.

(2) As a rule, CO2 first gets accommodated in plasma; when plasma becomes fully saturated, then it

is accommodated in the RBCs. thus, of the total 4 ml% of CO2 transported in the bolod, 60% (2.4 ml%) is transported in plasma and remaining40% (1.6ml%) within the RBCs.

(3) CO2 is carried in the plasma and RBCs in 3 forms: (i) In dissolved form (0.3 ml %) (ii) As cabamino compounds (0.7 ml %) (iii) As bicarbonate (3 ml %)

In dissolved form (0.3 ml %)

(a) In plasma

CO2 as it enters he plasma,

(1) a part goes to solution as CO2, and

(2) remaining in small amounts with water forms carbonic acid (H2 CO2).

CO2 +H2O ―――→ H2 CO3 This is a slow reaction because of absence of enzyme carbonic anhydrase (CA) in plasma and

only 0.2 ml % of CO2 is transported in plasma in dissolved form. (b) In RBCs

Here, CO2 gets rapidly hydrated to form H2 CO3 due to presence of enzyme CA in the RBCs.

However , only0.1 ml % of CO2 is transported in the RBCs in dissolved form.

As cabamino compounds (0.7 ml %)

(a) In plasma

CO2 combines directly with plasma proteins to form carbamino protein. It is a slow reaction so,

only 0.1 ml % of CO2 is transported this way.

CO2 +Pr NH2 → PrNHCOOH (b) In RBCs CO2 with amino group of haemoglobin forms carbamino haemoglobin; comparatively, a fast

reaction and 0.6 ml % of CO2 is transported in this way.

CO2 +HbNH2 →HbNHCOOH

As bicarbonate (3 ml %)

(a) In plasma

CO2 is carried in plasma s sodium bicarbonate (NaHCO3) - HCO3 and proteins both act as acid and complete for the base. During this process, proteins get + - reduced and some Na from proteins shifts to HCO3 forming NaHCO3. (b) In RBCs RBCs are rich in enzyme carbonic anhydrase (CA) , therefore, irreversible reaction takes place within 1-2 secs. - + - CO2 + H2O→ H2CO3 → H + HCO3

9. Chemo Receptors:

Repeated refer: Nov 2001, Aug 2005

10. Endothelins:

 Endothelin — A Powerful Vasoconstrictor in Damaged Blood Vessels.  Still another vasoconstrictor substance that ranks along with angiotensin and vasopressin in its vasoconstrictor capability is a large 21 amino acid peptide called endothelin, which requires only nanogram quantities to cause powerful vasoconstriction.  This substance is present in the endothelial cells of all or most blood vessels.  The usual stimulus for release is damage to the endothelium, such as that caused by crushing the tissues or injecting a traumatizing chemical into the blood vessel  After severe blood vessel damage, release of local endothelin and subsequent vasoconstriction helps to prevent extensive bleeding from arteries as large as 5 millimeters in diameter that might have been torn open by crushing injury.

Feb 2011 sub code 4054

Paper IV

I)

1.Cardiac output. Repeated

2. Visual pathway.

Repeated refer : Aug 2004, Aug 2007,08,09.

II)

1. ECG in lead II

Repeated refer: March 2002, Sep 2002

2. Regualtion of coronary blood flow

Repeated refer : March 2002 , Aug 2008

3. Compliance of lung

Repeated refer: Aug 2009

4. CO2 transport.

Repeated refer: Aug 2010

5. Dysbarism.

Repeated refer: Feb 2005,08,09,10

6. Functions of Thalamus.

Repeated refer: Aug 2008

7. REM sleep.

Repeated refer:

8. Decerebrate rigidity

Repeated refer: 9. Taste pathway.

Repeated refer:

10. Theories of hearing.

Repeated refer:

III)

1. Frank-starlings law of heart.

2. Short term regulation of BP.

Repeated refer: March 2002,Sep 2002

3. Intrapleural pressure.

- Pleural pressure is the pressure of the fluid in the thin space between the lung pleura and the chest wall pleura. - As noted earlier, this is normally a slight suction, which means a slightly negative pressure. - The normal pleural pressure at the beginning of inspiration is about –5 centimeters of water, which is the amount of suction required to hold the lungs open to their resting level. - Then, during normal inspiration, expansion of the chest cage pulls outward on the lungs with greater force and creates more negative pressure, to an average of about –7.5 centimeters of water. - These relationships between pleural pressure and changing lung volume - showing in the lower panel the increasing negativity of the pleural pressure from –5 to –7.5 during inspiration and in the upper panel an increase in lung volume of 0.5 liter.

- Then, during expiration, the events are essentially reversed.

4. Dead space

Some of the air a person breathes never reaches the gas exchange areas but simply fills respiratory passages where gas exchange does not occur, such as the nose, pharynx, and trachea.This air is called dead space air because it is not useful for gas exchange. On expiration, the air in the dead space is expired first, before any of the air from the alveoli reaches the atmosphere. Therefore, the dead space is very disadvantageous for removing the expiratory gases from the lungs.

5. Histotoxic hypoxia

Repeated refer: April 2001

6. Bell megendie law.

All the motor fibers in spinal cord will arise from anterior grey horn and the sensory fibers will arise from posterior grey horn.

7. Functions of RAS.

Sleep Wake cycle and Alertness.

8. Functions of prefrontal lobe.

Higher intellectual functions,

Memory, analytical skills reasoning etc.

9. Endocochlear potentials.

Endo cochlear presentation is the positive voltage of 80-100mV seen in the cochlear endolymphatic spaces.Within the cochlea the EP varies in the magnitude all along its length. When a sound is presented, the endocochlear potential changes either positive or negative in the endolymph, depending on the stimulus

10. Delta waves in EEG.

Repeated refer: Feb 2008, Aug 2006

Paper IV August 2011 Sub code : 4054

I) Essay

1) Functional divisions of cerebellum:

(i) Vestibulocerebellum:

- flocculo nodular lobe

(ii) spinocerebellum:

- Lobus simplex, pyramis, uvula and para floccule

(iii) cortico or neocerebellum;

Remaining part of the posterior lobe.

Structure, connections and functions:

- Cerebellar cortex consist of o Outer molecular layer o Middle purkinje cell layer o Inner granule cell layer

- Nuclei of cerebellum o Emboliformis o Fastigus nuclei o Globosus o Dentate nucleus

Molecular, purkinje and granular layer has climbing, mossy and parallel fibers.

Connection and functions:

(i) Afferent connections: a. Dorsal spinocerebellar tract b. Ventral spinocerebellar tract c. Olivo cerebellar tract d. Vestibule cerebellar tract e. Cuneo cerebellar tract f. Cortico – ponto – cerebellar tract.

(ii) Efferent connections: a. Dento thalamic tract b. Dento rubral tract c. Festigo bulbar tract

Functions of cerebellum: (ii) control of body posture and equilibrium (iii) control of muscle tone & stretchy reflexes (iv) Control of co – ordinated movement of the body (v) Control of voluntary fine movements a. Servo mechanism b. Comparator function c. Damping action Two signs of cerebellar lesions: - Pendular knee jerk - Ataxic gait - Intentional tremor 2. Structure & function of conducting system

SA node ( pace maker of the heart ) 0.05 m / s

Internodal fibers 1.0 m/ s

Wenchebach Bachman Thorel

AV node 0.05 m / s

Bundle of His 1.0 m / s

Right Bundle Left Bundle branch 4.0 m /s

Purkinjee fibers

Then the impulses spread into the ventricular muscles.

Functions:

- SA node is the pace maker of the heart - Normally it can produce impulse at a rate of 60 to 80 / min - SA node has an unstable RMP if – 55 mV, so it has the property of ‗ autorhythicity‘.

AV nodal delay:

- the rate of transmission of impulse from atrium to ventricles via AV node is 0.05 mt / sec - there is a delay of about 0.1 sec Significance: - somplete emptying of atrium into ventricles - ventricles contract after the atrium

Properties of Cardiac muscles; - Excitability - Autorhymicity - Conductivity - Contractability.

II) 1. Non respiratory functions of respiratory tract:

- Nasal mucosa form the receptors for olfaction - Humidification of atmospheric air - Filtering of dust particles below 10 microns in diameter - Protective reflexes – sneezing reflex - Defence mechanism – pulmonary alveolar macrophages - Pulmonary circulation acts as a reservoir for left ventricle - Synthesis of surfactant to prevent the alveolar collapse - Lungs secrete angiotensin converting enzyme.

2. Functional residual capacity:

It is the volume of air contained in the lung at the end of expiration.

FRC = TV + ERV = 2.5 L Measurement:

b) Open circuit - nitrogen washout method c) Closed circuit – helium dilution technique

Clinical significance:

- FRC maintains RV constant. - If no FRC then during inspiration gaseous exchange is maximum and during expiration it is nil. - Hence FRC acts as a buffer. - It prevents drastic change in composition of alveolar air.

3. Artificial respiration

Repeated refer: Aug 2004, 08

4. Referred pain

Repeated refer: Aug 2006

5. Special features of coronary circulation

Repeated refer: Aug 2010

6. Colour vision

Vision is of 2 types: - Achromatic – sensation of white vision - Chromatic - spectral colour vision The 3 primary colours are: Red, Green and blue

Theories of colour vision: (i) Thomas young & von helmholtz‘s theory

Basis of three colours – based on 3 cone receptors – different photosensitive pigments

(ii) Muller‘s doctrine of specific nerve energies

Specific nerve fibers with specific ganglion cells to three primary colours

(iii) Granit‘s theory:

Range of wavelength of light to visual mechanism 395 – 700 nm Some cones wide spectrum of sensitivity and are dominator receptors & some cone to narrow range are modulator receptors.

7. Taste pathway:

Repeated refer: April 01, March 02

8. Dark adaptation

Repeated refer: Aug 08, Nov 01

9. Myasthenia gravis

Repeated refer: Feb 2005

10. Brown sequard syndrome:

Repeated refer: Aug 2008

III) 1) Diagram of alveocapillary membrane:

2) SCUBA - self contained underwater breathing apparatus - consist of cylinder with compressed air with valve system.

3) J receptors & significance; - AS paintal 1955 discovered it - They are sensitive to content of interstitial fluid ie) pulmonary congestion and edema - It produces reflex apnea followed by tachypnea, hypotension & bradycardia

4) Otolith organs: Refer; Aug 05, April 2001

5) Alpha block: Refer: Aug 2008

6) Frank starling‘s law:

Force of contraction is directly proportional to initial length of muscle fiber under physiological limits.

7) Monro kille doctrine law:

Intra cranial pressure is regulated by three components - CSF pressure - Brain tissue and - ECF and blood

Any of the component compromise to maintain the ICP constant.

8) Stereognosis:

Ability of an individual to recognize the known objects with eyes closed by use of touch & pressure sensation Center parietal lobe area 3, 1, 2

9) Functions of frontal lobe;

Pre frontal lobe: Higher intellectual functions Memory Reasoning Analytical sklll Premotor cortex: Voluntary motor activites Fine precise activities.

10) Mechanoreceptors: These are receptors which respond to mechanical changes. Eg. Pressure changes They convert the pressure changes into electronic potentials Eg. Baroreceptors

11) Summation: Subminimal stimulus cannot provoke an action potential but when repeated sub minimal stimulus of low threshold is given repeatedly because of summation they produce response. Types: Temporal summation Spatial summation

12) Cholinergic receptors; Receptors that respond to Ach Muscuranic receptors Nicotinic receptors

Adrenergic receptors: Receptors that respond to adrenaline and nor adrenaline Alpha 1 and Alpha 2 Beta I and Beta 2

13) Rods and Cones:

14) Spasticity Rigidity

(i) Pyramidal lesions (i) Extrapyramidal lesions

(ii) affects one group of muscles (ii) Both the groups of muscles involed

Eg. Stroke Eg. Parkinson‘s disese

15) Histotoxic hypoxia:

Refer: Feb 2007, Aug 2008