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Home , Epineurium, Gray ramus communicans, Ramus communicans, White ramus communicans

LECTURE OUTLINE CHAPTER 13 Marieb The : The Brain and Spinal Cord Lecture Outline

BRAIN

I. Introduction to the Organization of the Brain

This pattern can be generalized further to say that the lowest (most inferior) parts control the bare necessities for life - regulation of heartbeat, digestion, etc. The next levels up are the location for primal drives and emotions - rage, fear, sex drive, hunger, etc. The most superior level, top of the brain, is intellectual thought, imagination, perception, interpretation, and appreciation of sensations, and control and modulation of emotions. An infant apparently starts out using mostly the lowest, then the next, and finally the upper parts of its brain. (The terrible twos, threes and beyond evidence the emotional part over which parents attempt to help the child establish third level control - a veneer of civilization)

II. Major Regions of the Brain A. Cerebrum (telencephalon) 1. two hemispheres separated by longitudinal fissure 2. gyrus separated by sulcus 3. gray surface with white tracts internally a. commissure – connect corresponding gyri of the two hemispheres 1) corpus callosum b. projection tracts – connect more or less vertically c. association tracts – connect one gyrus to another in the same hemisphere 4. lobes – named for covering bones a. frontal b. parietal c. temporal d. occipital e. insula - hidden deep to temporal lobe B. Diencephalon 1. epithalamus ( pineal gland) 2. thalamus 3. hypothalamus C. Cerebellum (metencephalon) 1. two hemispheres, gray surface 2. folia – ridges on surface separated by sulci 3. arbor vita – white tracts D. Brainstem ( (myelencephalon)

1 1. medulla oblongata a. pyramids - decussation or crossing over 2. pons 3. midbrain III. Overall Organization A. Portions closely attached to spinal cord are white on the outside with gray material internally. Less conscious awareness of activity occurs there B. Ventricles – cavities 1. make / contain cerebrospinal fluid (CSF) a. choroid plexus with b. ependymal cells line the ventricles 2. two lateral ventricles either side of thalamus, drains by interventricular foramen into- 3. third ventricle which drains by cerebral aqueduct to - 4. fourth ventricle 5. CSF circulates in sub arachnoid space and is reabsorbed 6. into superior sagittal sinus by arachnoid villi (granulations) C.. (See previous chapter) 1. - strong, "tough mother" a. falx cerebri - between cerebral hemispheres b. falx cerebelli - between cerebellar hemispheres c. tentorum cerebelli - between cerebrum and cerebellum 2. arachnoid - spidery, holds blood vessels 3. pia mater - "delicate mother" D. Cerebrospinal fluid (CSF) 1. functions a. “floats” the brain; shock- absorbing, cushioning b. transports nutrients, wastes, other chemicals 2. formation a. choroid plexus - network of capillaries and b. ependymal cells - which selectively take blood components to form CSF 3. Reabsorption through arachnoid granulations E. Cerebral cortex --Lobes named according to overlying skull bones 1. gray, final processing region for input 2. many regions - exact regions are imprecise a. visual area b. visual association area c. auditory area d. auditory association area e. precentral ( primary motor ) cortex f. postcentral (primary sensory) cortex g. premotor cortex h. prefrontal cortex F. White tracts internally

2 1. commissure – connect corresponding gyri of the two hemispheres a. corpus callosum 2. projection tracts – connect more or less vertically, form internal capsule 3. association tracts – connect one gyrus to another in the same hemisphere G. Cerebral nuclei - gray matter internal to the cerebral cortex, part of the extrapyramidal system 1. caudate nucleus - deep to lateral ventricles, maintains the pattern and rhythm of a movement 2. amygdaloid nucelus - almond shaped, near tail of caudate nucleus, part of limbic system (emotional brain) 3. claustrum - between insula and diencephalon, focuses visual attention 4. lentiform nucleus - bean shaped made up of - a. putamen - with claustrum b. globus pallidus - with claustrum and putamen, controls and adjusts muscle tone 5. corpus striatum -encloses both lentiform and caudate nuclei H. Functional brain systems 1. limbic system a. functions– emotional brain, links conscious and unconscious functions b. components - limbic lobe made up of - cingualte gyrus, dentate gyrus, parahippocampal gyrus, hippocampus, fornix, mamillary bodies, and anterior nucleus 2. RAS –reticular activating system – determines levels of alertness, composed of mesencephalon and network of nuclei IV. Diencephalon A. Epithalamus 1. pineal gland - produces melatonin, sets diurnal cycles B. Thalamus 1. structure - a. two lobes - third ventricle between these b. massa intermedia - connecting strand 2. functions a. anterior nuclei - part of limbic system, information relay b. medial nuclei - conscious awareness of emotional state, integrate sensory information, relay to frontal lobes c. ventral nuclei - relay information to and from central nuclei and cerebral cortex i. ventral posterior - relays sensory information ii. ventral lateral - relays somatic information to and from primary motor cortex d. posterior nuclei -

3 i. pulvinar - integrates sensory information to association areas ii. lateral geniculate - relays visual information iii. medial geniculate - relay auditory information to association areas e. lateral nuclei - feedback, integrates emotional with sensory information C. Hypothalamus 1. structure a. just superior to optic chiasma b. infundibulum - connects to pituitary gland c. tuber cinereum - between infundibulum and mamillary bodies, gray matter, controls pituitary d. median eminence - part of tuber cinereum 2. functions a. control of involuntary somatic motor activites, expressions of emotional states b. control of c. coordination of nervous and endocrine systems d. secretion of hormones - ADH (from supraoptic nuclei) and oxytocin (from paraventricular nuclei) e. produces emotional and basic drives - hunger, thirst, sex, anger, etc. f. coordinates voluntary and autonomic activity g. regulates body temperature h. controls diurnal rhythms V. Mesencephalon - midbrain A. Structure and functions 1. corpora quadrigemina a. superior colliculus - processes visual information b. inferior colliculus - relays auditory information to thalamus 2. tectum - roof of fourth ventricle 3. red nucleus - involuntary muscle activity for posture, etc 4. substantia nigra -regulates motor output 5.cerebral peduncles - ascending and descending tracts to thalamus VI. Pons A. Sensory and motor nuclei for 4 cranial (V, VI, VII, and VIII) B. Nuclei for Involuntary control of respiration 1. apneustic center 2. pneumotaxic center - together regulate lung inflation and breathing rhythms C. Nuclei which relay cerebellar information through cerebral peduncles D. Tracts - ascending, descending and transverse - permits communication between cerebellar hemispheres VII. Cerebellum

4 A. Structure 1. hemispheres, separated by vermis 2. lobes - 2 each hemisphere, separated by primary fissure a. anterior b. posterior c. small flocculomotor - anterior and inferior to major lobes 3. cortex -gray surface with a. folia - fine ridges b. sulcus - grooves between the ridges c. Purkinje cells , of which become- 4. arbor vitae () in center 5. cerebellar nuclei - synapsing of sensory information for motion 6. superior cerebellar peduncles - link tocerebrum, diencephalon and mesencephalon 7. middle cerebellar peduncles - connect to motor and sensory centers of pons 8. inferior cerebellar peduncles - link to medulla, carry ascending and descending tracts B. Functions 1. postural muscles control ( by way of red nucleus) 2. fine control and coordination of voluntary and involuntary movements VIII. Medulla Oblongata continuous with spinal cord A. Structure 1. gray matter a. nucleus gracilis - relay sensory information to thalamus b. nucleus cuneatus - as above c. olivary nuclei - relay to cerebellum from all other regions d. nuclei of cranial nerves numbers VIII, IX, X, XI, and XII e. reflex centers - autonomic system i. cardiovascular center - includes cardiac and vasomotor centers - regulate rate, pressure, etc. ii. respiratory rhythmicity center - self explanatory 2. white matter a. ascending tracts - sensory information b. descending tracts - motor information

SPINAL CORD

I. Spinal cord A. longitudinal organization 1. bilateral symmetry 2. cervical and lumbar enlargements - associated with more cell bodies for motor control of limbs 3. anterior fissures 4. posterior sulcus

5 5. central canal, containing CSF 6. superficial white (myelinated) tracts/columns a. anterior and lateral descending b. posterior and lateral ascending 7. interior gray horns a. cell bodies, and 8. 31 pairs of spinal nerves – named after the inferior vertebra a. 8 cervical b. 12 thoracic c. 5 lumbar d. 5 sacral 9. conus medullaris - inferior end of spinal cord proper 10. cauda equina - individual spinal nerves within 11. filum terminale - filamentous end of meninges, "tie-down" B. Coverings - meninges 1. dura mater - "tough mother", strong 2. sub dural space 3. arachnoid meninx - spidery looking, carries blood vessels, etc. 4. subarachnoid space 5. pia mater - "delicate mother", adheres tightly to surface of spinal cord C. Organization of cross section of cord 1. Gray matter - interior horns a. posterior - somatic and visceral sensory nuclei b. anterior gray horns - somatic motor control c. lateral gray horns - visceral motor control d. gray commissures - axons carrying information from side to side 2. White matter - tracts or columns a. positions i. posterior white column - ii. anterior white column iii. lateral white column iv. anterior white commissure b. functions i. ascending tracts - sensory toward brain ii. descending tracts - motor from brain E. Nerves - definition – bundles of axons , AKA tracts in CNS F. Organization 1. coverings – similar to muscles a - wraps entire b. - wraps fascicles of tracts c. - wraps individual axons 2. function a. sensory - afferent b. motor - efferent

6 c. mixed - contains axons of both G. Dermatomes Sensory innervation by specific spinal nerves H. . Organization of each 1. root – inside vertebral canal a. dorsal sensory root with a b. ventral motor 2. mixed spinal nerve 3. rami a. dorsal mixed b. ventral mixed “spinal nerve” c. white motor ANS d. motor ANS I. Plexus – braid of ventral rami of cervical, thoracic, lumbar or sacral spinal nerves 1. cervical a. phrenic nerve - innervates diaphragm 2. brachial a. trunks - superior, middle, and inferior b. cords - lateral, medial, and posterior i. musculocutaneous nerve - innervates biceps and brachialis muscles ii. median nerve - innervates lateral flexors iii. ulnar nerve - innervates medial flexors iv. axillary nerve - innervates deltoid muscle v. radial nerve - innervates forearm extensors 3. lumbar a. genitofemoral nerve b. lateral femoral cutaneous nerve c. femoral nerve 4. sacral a. lumbosacral trunk i. sciatic nerve ii. pudendal nerve iii. common peroneal nerve iv. tibial nerve J. Reflexes – fast, stereotypical, inborn, protective actions 1. occur at spinal cord or brainstem levels 2. do NOT require cerebral processing but can be modified by cerebral control 3. may be either monosynaptic or polysynaptic but either is relatively simple 4. may be either somatic or visceral 5. all require - a. stimulus at receptor b. sensory information relay

7 c. processing at CNS level d. activation of motor response e. response of peripheral effector 6. examples a. patellar b. stretch reflex

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