Physiology of the

Motor division of the CNS

Reflex General function of the nervous system (NS)

Nervous system -communication network of neurons that allows the organism to interact with the environment (external, internal)

• main function: regulation of body functions

• purpose: adaptation to changes - maintenance http://www.alz.org/braintour/images/neuron_forest.jpg of homeostasis and survival

1. Peripheral NS 2. Central nervous system Levels of the CNS

• - conducts sensory information to the brain  - conducts motor information to the effector organs  - serves as a simple regulatory centre () - damage of the spinal cord breaks down the connection between periphery and higher centres – serious consequences

• Brain - subcortical level - control of involuntary and subconscious functions

- brain cortex - control of voluntary functions - control of lower levels of CNS - site of cognitive (higher) functions: memory, learning, thinking Peripheral nervous system (PNS)

- transmits information from periphery to the central nervous system and vice versa

Includes - – originate in brain (I – XII) - spinal nerves - originate in spinal cord (C1, C2...Th,..L, S..)

Components A. afferent (sensory) nervous system (incoming to CNS) B. efferent (motor) nervous system (outgoing from CNS)

a. somatic nervous system (transmit impulses to ) b. autonomic nervous system (transmit impulses to smooth muscles, cardiac muscle and glands)

I. sympathetic division (fight or flight) II. parasympathetic division (rest and repair) Motor functions and their regulation

Spinal reflexes - simple movements – movements

Brainstem – posture control, hand and eye movements

Cerebellum - making movements „smooth“ - precisely regulates the sequence and duration of the elementary movements of each of these segments

Basal ganglia - regulation of well co-ordinated voluntary movements - cognitive control of voluntary movements (e.g. running away from a dangerous animal)

Brain cortex – motor areas (primary, premotor, supple- mentary motor) decision about voluntary movements

Knee jerk – the

- tap on the tendon of m. quadriceps femoris - the leg makes a „kick“ (extension in knee joint occurs) Reflex

• definition: predictable, quick, stereotyped and involuntary response to stimulus • action that results from passing a nerve impulse over a • „lowest level“ of regulation of motor functions

Reflex arc – the basic circuit that underlies a reflex: 1. sensory receptor – gathers stimuli 2. afferent nervous fibre – signal transduction into CNS 3. reflex (integration) centre – processes information 4. efferent nerve fibre – transduction of response 5. effector (muscle, gland)– performance, response to the stimulus

Spinal reflex arc Classification of reflexes – with respect to: A/ Count of synapses: 1. Monosynaptic - 1 synapse in the reflex arc

2. Polysynaptic = 2 or more synapses in reflex arc

https://s-media-cache-ak0.pinimg.com/originals/a6/41/3f/a6413f649558834e5541fb7e03124f54.jpg Classification of reflexes – with respect to:

B/ Type of sensory receptor Exteroceptive – receptor in the reflex arc is an exteroceptor (gathers stimuli from external environment) Proprioceptive – receptor in the reflex arc is an proprioceptor (gathers stimuli about position of the body) Interoceptive – receptor in the reflex arc is an proprioceptor (gather stimuli from internal environment)

C/ Integration (reflex) centre Cranial – centre in nuclei of the cranial nerves Spinal – centre in the spinal cord Extracentral – integration centre in autonomic ganglia

D/ Effector Somatic – effector: skeletal muscle Autonomic (visceral) – effector: cardiac muscle, smooth muscle, gland

E/ Origin Inborn – related to locomotion, defence, food intake, sexual behaviour Acquired – develop during life Spinal reflexes

Spinal reflexes include - the muscle - the Golgi - the - the Muscle stretch reflexes (myotatic)

• monosynaptic • spinal reflexes – refelex centre in the spinal cord • example: knee jerk • involved in regulation of movement, muscle tone and posture – • in part conscious • to major extent - subconscious reflex or automatic action – includes spinal reflexes

• both receptor and effector are in the same muscle

• types of sensory receptors involved in spinal reflexes: – a – Golgi tendon organs The muscle spindle

•a stretch receptor in a muscle •a bundle of modified muscle fibres encased in a capsule

Polar parts of the muscle spindle - composed of intrafusal fibres that are contractile (can respond to a stimulation by contraction)

Central part of the muscle spindle - fibres non contractile – does not respond to stimulation by a contraction - can be passively stretched - a is wrapped around the fibres

• adequate stimulus for the muscle spindle: muscle stretch

- potential is transmitted via the sensory nerve muscle stretch to the reflex centre c • response – contraction of the extrafusal c

muscle fibres of the same muscle

Muscle stretch reflexes – reflex arc • tapping on the muscle tendon (of different muscles)  passive prolongation of the muscle and also of the muscle spidle = stimulation(1) • is transmitted by afferent fibre (2) • afferent fibre enters spinal cord through posterior roots c c • afferent fibre synapses with efferent fibre (a – motoneuron) • synapse = integration centre (3) (information is processed) • action potential is transmitted by efferent fibre (a – motoneuron) Tap the tendon, also the muscle and muscle into muscles (via the motor endplate) (4) spindle is prolonged • muscle contraction occurs (5-response) - this is seen as movement (muscle contraction)

• a proprioceptive sensory receptor • located at the insertion of skeletal muscle fibers into the tendons of skeletal muscle • made up of strands of collagen connected at one end to the muscle and at the other with the tendon • when the muscle contracts, the collagen fibrils are pulled tight, and this activates the Golgi tendon organ afferent • it detects tension of the muscle The (inverse myotatic reflex, polysynaptic)

- receptor: Golgi tendon organ (can be stimulated by very strong contraction or stretching)

- signal transmitted via afferent nerve fibre and by (inhibitory) in spinal cord to alpha motorneurons

- efferent fibre: alpha motoneuron – it gets inhibited !!!

- response: muscle relaxation (the same muscle where the receptor is located)

- function: protection against rupture of the muscle

https://acewebcontent.azureedge.net/blogs/blog-examprep-031615-2.png Withdrawal reflex (polysynaptic)

-stimulus causes response in both flexors and extensors of the same side: 1. activation of alpha motoneurons of the ipsilateral flexor muscles, 2. at the same time inhibits alpha motoneurons that supply antagonistic extensor muscles - example: when touching a hot object – contraction of flexors and relaxation of extensors causes removing the hand Crossed extension reflex – polysynaptic

- a stimulus causes response on both sides in bots extensors and flexors: 1.activation of alpha motoneurons of the ipsilateral flexor muscles 2.inhibits alpha motoneurons that supply antagonistic extensor muscles

- the opposite pattern occurs on contralateral side 3.flexors are inhibited 4.extensors are stimulated

- example: when a person steps on a nail, the leg that is stepping on the nail pulls away, while the other leg takes the weight of the whole body- reflex enhances postural support - example: locomotor pattern generator Spinal cord

• segmental organization • segments (levels) of the spinal cord contain regulatory circuits involved in control of the movements of a particular region of the body • muscle stretch reflexes have their inegration centres in different segments of the spinal cord

Muscles in axial parts of the body limbs (a motoneurons medial part) (a motoneurons -lateral part) = somatotopic organization Examination of reflexes in a human

• basic examination in neurology • indicates the function of reflex arc (and all its components) • reflex - stereotypic reaction = predicted response • normoreflexia – normal reflex response on a stimulus

• abnormal response indicates disorder in a part of reflex arc

Types of abnormal results: • hyperreflexia (or clonus) – hyperactive reflex • hyporeflexia – diminished reflex • areflexia – absence of response • abnormal reflex – the response on the stimulation is abnormal Task: Examination of reflexes in a human

Principle • sensory receptors are stimulated • the reflex response on stimulation is observed and evaluated

Procedure • the patient is in sitting or lying position (depends on the reflex)

• sensory receptors are stimulated by a reflex hammer, cotton, light, needle (depends on the reflex that we want to examine)

• examine following reflexes (see next slides)

Reflex examination video https://www.youtube.com/watch?v=eqOpNQH09pA Proprioceptive (deep tendon) reflexes - sensory receptor – in muscle, tendon

• Masseter reflex (n V) S: tap on a spatula put on the lower jaw (mouth is moderately open) R: closing the mouth

• Naso-palpebral reflex (n V,VII) S: tap on the nasal base R: closing of eyelids

• (C5) S: tap on lacerus fibrosus m. bic. brachii R: flexion of the forearm

• (C7) S: tap on olecranon ulnae R: extension of the forearm • Styloradial (brachioradial)reflex (C7) S: tap on proc. styloideus radii R: flexion of forearm

• Patellar reflex (knee jerk, L 2-4) S: tap on the tendon of m. quadriceps femoris R: extension in knee joint - the patient is sitting, and the examined limb is put over the knee of the other - if no response occurs, do the Jendrassik manoeuver (abduce one hand from another)

• Achilles tendon reflex (ankle jerk, L5-S2) S: tap on Achilles tendon R: extension of the foot - the patient may lie or kneel

Achilles tendon reflex measurement

Principle: - thyroid hormones (thyroxin, triiodthyronine) influence the activity of the central nervous system - examination of Achilles tendon reflex is an indirect indicator of thyroid activity (Ankle jerk) - reflex time (stimulation – response) depends directly on the level of thyroid hormones

- normal reflex response – euthyrosis - weak response – hypothyrosis - excessive response – hyperthyrosis

Exteroceptive reflexes - sensory receptors in skin or mucosa

Corneal reflex (n V, VII) S: touching the cornea with a piece of cotton R: blinking (used in surgery-depth of anaesthesia, is the last to disappear in deepening anesthesia)

Abdominal reflexes (Th 5 – Th 11)

• epigastric • mesogastric • hypogastric

S: drawing of the abdominal wall with a needle R: muscle contraction (lying position) (L5-S2) S: stimulation of external side of planta pedis with a needle (from heel to little finger and other fingers) R: plantar flexion or the toe (or all fingers)

- if pyramidal pathway is impaired the response in plantar reflex is abnormal (this is called Babinski phenomenon) R: extension of the toe - normal in babies up to 6-8 months, later a sign of disorder - indicates abnormalities in pyramidal tract Autonomic (vegetative) reflexes - response – transmitted by autonomic fibres

• Pupilary light reflex S: illumination of an eye (use battery) R: miosis – diameter of the pupil becomes narrow - consensual reaction – if one eye is illuminated, miosis occur bilaterally

• Oculocardial reflex S: moderate pressure on the eyeball R: decrease in pulse frequency (by 5-10 beats per minute) • Orthostatic reflex S: sudden change position from lying to sitting R: increase in pulse frequency • Solar reflex S: pressure against solar plexus R: drop in pulse frequency

– all reflexes- measure heart rate only 15´´, then multiply by 4 (rate per min) Neurons of the spinal grey matter

 a motor neurons - their leave via ventral roots (and cranial nerves) and terminate in muscles (on the motor end-plate) - discharge of a a-motor neurons causes a skeletal muscle contraction - synapse with sensory neurons, interneurons, neurons descending from brain (pyramidal pathway)

 g motor neurons - innervate muscle fibres of the muscle spindles (intrafusal muscle fibres)

- control of muscle tone pyramidal extrapyramidal - receive input from decending neurons of extrapyramidal pathways

 interneurons

 propriospinal neurons - short fibres, - synapse within the spinal cord - vertical connections

Alpha-gamma co - activation

• gamma motor neurons – adjust the Gamma fibre sensitivity of the muscle spindle • gamma – fibres – terminate in the polar parts of muscle spindle

• the stimulation by gamma fibres causes Gamma contraction of muscle fibres in the polar region fibre (periphery) of the muscle spindle Receptor potential of a muscle spindle can be • the fibres in the centre (equatorial region) elicited by: become prolonged 1/A passive stretch (e.g. tapping with the reflex hammer) – passive prolongation of the central part = stimulus – elicits a muscle stretch reflex that rest results in contraction of the muscle

• response - muscle contraction 2. Active stretch - intrafusal muscle contraction • In this way the muscle tone is regulated caused by gamma innervation – prolongation of the central part (muscle tone = partial contraction of the muscle) Alpha-gamma co - activation

• a loop for regulation of the muscle tone

• extrapyramidal pathways terminate on the - gamma motor neurons in the spinal cord gamma motor Gamma • axons of gamma motor neurons terminate in neuron - fibre the polar parts of muscle spindle • the stimulation by gamma motor neurons causes contraction of muscle fibres in the polar region (periphery) of the muscle spindle • the fibres in the centre (equatorial region) become prolonged = stimulus – that elicits a muscle stretch reflex that results in contraction of the muscle

• response - muscle contraction • In this way the muscle tone is regulated Monosynaptic reflex arc

Autonomic reflex arc (efferent pathway – 2 neurons – connected in ganglia)

The cerebellum is important in balance and in planning and executing voluntary movement.

Cerebellum • an important control center for motor function – rate, range, force and direction of the movements • contains as many neurons as the rest of the brain

1. vestibulocerebellum (archicerebellum) - regulates balance and eye movements 2. spinocerebellum (paleocerebellum) - regulates synergy of the body and limb movements + is able to elaborate proprioceptive input in order to anticipate the future position of the body 3. cerebrocerebellum (neocerebellum) involved in planning and initiation of movements Examination of the cerebellum

Scanning speech • Scanning speech refers to slow, slurred, monotonous, and irregular speech that is associated with dysarthria due to oral motor ataxia. Causes enunciation of individual syllables. • Test: Ask the patient to say: “the British parliament”. In case of scanning speech it becomes “the Brit-tish Par-la-ment.”

Nystagmus • Ocular findings are generally less prominent, but ipsilateral gaze- evoked nystagmus are is seen with fast phase toward side of cerebellar lesion. • Test: Ask the patient to follow your finger and observe presence of nystagmus.

http://stanfordmedicine25.stanford.edu/the25/cerebellar.html Dysmetria (Finger to nose & finger to finger test) • Limb ataxia is usually seen clinically as difficulty with coordinated tasks. • Test: Ask patient to fully extend arm then touch nose or ask them to touch their nose then fully extend to touch your finger. You increase the difficulty of this test by adding resistance to the patient's movements or move your finger to different locations. Abnormality of this is called dysmetria.

Rebound phenomenon • If the patient pulls on your hand and when you slip your hand out of their grasp, normally the antagonist muscles will contract and stop their arm from moving in the desired direction. • In cerebellar disease this response is completely absent causing to limb to continue moving in the desired direction. • Test: Have the patient pull on your hand and when they do, slip your hand out of their grasp. Observe the presence of rebound phenomenon. (Be careful that you protect the patient from the unarrested movement causing them to strike themselves.)

Rapid alternating movements • Common finding in cerebellar disease is dysdiadochokinesia (incoordination when performing rapid alternating movements). • Test: Ask patient to place one hand over the next and have them flip one hand back and forth (pronate and supinate) as fast as possible (alternatively you can ask the patient to quickly tap their foot on the floor as fast as possible).

Hypotonia • Low muscle tone may be present in cerebellar diesases. • Test: Perform the examination of the patellar reflex (knee jerk). “Pendular” knee jerk, leg keeps swinging after knee jerk more than 4 times (4 or less is normal).

Gait • Test: Ask the patient to walk straight forward • In cerebellar disorders – the gait is commonly wide based and staggering. They may fall to the side of the lesion.

Romberg’s test • Whilst Rombergs test does not directly test for cerebellar ataxia, it helps to differentiate cerebellar ataxia from sensory ataxia. In cerebellar ataxia the patient is likely to be unsteady on their feet even with the eyes open.

• Test: Perform Romberg’s test by asking the patient to stand unaided with their eyes closed and heels together. • If the patient sways (titubation) or loses balance then this test is positive. Stand near the patient in case they fall. Regulation of the motor functions – Brain cortex

• Primary motor cortex - precentral gyrus in the frontal lobe – Large neurons (pyramidal cells) allow conscious control of movement of individual skeletal muscles – The pyramidal cells' long axons form pyramidal (corticospinal) tracts – Motor areas have been spatially mapped = somatotropy (motor homunculus)

• Premotor cortex - anterior to the precentral gyrus in the frontal lobe – Regions controls learned motor skills that are repeated or patterned – Also coordinates the movements of several muscles simultaneously and\or sequentially by sending activating impulses to the primary motor cortex • Broca's area - anterior to the premotor area – Involved in directing motor speech

• Frontal eye field - anterior to the premotor cortex and superior to Broca's area – Controls voluntary movement of eyes.

Volunary movement

• Multiple association areas of the cerebral cortex - motivation, ideas to produce motor activity

• Supplementary and premotor cortex – development of a motor plan – Identification of the specific muscles that need to contract and their sequence

• Primary cortex cortex - upper motorneurons

• Spinal cord • Lower motorneurons

Motor homunculus

At the primary motor cortex, motor representation of the body is arranged in an orderly manner. The amount of cortex devoted to any given body region is proportional to how richly innervated that region is (not to the body region's physical size). Areas of the body with greater or more complex motor connections are represented as larger in the homunculus, the resulting image is that of a distorted human body, with disproportionately huge hands, lips, and face. Lateralization of brain functions

Old concept -Left hemisphere is dominant because it controls the dominant hand

Current concept - generally, each hemisphere's structure is mirrored by the other side - despite strong similarities, the functions of each hemisphere differ Left hemisphere functions - verbal functions: speech, reading, writing - langue – grammar, spelling - mathematics – analytical thinking, counting and measurement - logical thinking - complex voluntary motor functions - sequential approach

Right hemisphere functions - complex sensory perception (music, dance) - site of spatial abilities - fantasy, art - visual memory - face recognition Males - language – intonation, accentuation – exhibit more lateralization - simultaneous, holistic approach Females – more bilateral

Task: Assessment of motor handedness

• handedness - the preference of one hand over the other

• usually one hand is considered dominant

• most people are right-handed (90% of population)

• some individuals exhibit the ability to use both hands equally (ambidexterity)

• preference for one hand is most likely the effect of brain lateralization

• handedness has a genetic basis, it is also influenced by socio-cultural pressures

http://www.well.ox.ac.uk/_asset/image/nov-10-handedness-and-language.jpeg/fit/460/768 - read the inventory questions and respond to each by filling a number into the box

Please mark the box that best describes which hand you use for the activity in question

Always Usually No Usually Always Left (-50) Left (-25) Preference (0) Right (25) Right (50) Writing (a letter)

Throwing (a ball)

Scissors

Toothbrush

Knife (without fork)

Spoon

Match (when striking)

Computer mouse Result: - by making a sum of all numbers you get a score of Laterality Quotient (LQ)

- evaluation: righthanded LQ: +400 to +200 lefthanded LQ: -400 to -200, mixed handedness LQ: -200 to +200.

Conclusion: Comment on your motor hand preference:

No Always Usually Usually Always Preference Left (-50) Left (-25) Right (25) Right (50) (0) Writing (a letter) Throwing (a ball) Scissors Toothbrush Knife (without fork) Spoon Match (when striking) Computer mouse