Nervous System ( 5% )

Question 1

Visual pathways

• Have P cells that are associated with colour.
• Utilize the primary colours red, yellow and blue.
• Have simple cells which respond to all light stimuli
• Pass through the medial geniculate body.
• Have a temporal path for motion.

Answer 1

Have P cells that are associated with colour.

(aka parvocellular cells, located in the Lateral Geniculate Nucleus. involved in colour transmission)

• Utilise the primary colours red, green, and blue
• Have multiple cell-types, each responding to a different type of stimuli (rods and cones etc)
  
  • ​Rods respond to lower light intensities (night / scotopic vision) but distinguish higher intensities poorly, hence contribute less to visual acuity. Cones are the opposite
• Pass through the lateral geniculate body
• Have a temporal path for recognition of forms and faces. Output from V1 can go to the parietal lobe (motion) or temporal.

Question 2

parasympathetic stimulation causes

• sweat secretion
• salivary secretion
• inhibition of peristalsis
• increase in HR
• vasoconstriction of abdominal viscera

Answer 2

salivary secretion

Sympathetic = fight or flight

Parasympathetic = eat and secrete

= rest and digest

= feed and breed

Question 3

A sense organ for pain is

• Merkel’s disc.
• Kranse end bulb
• Naked nerve endings
• Meissner’s corpuscle
• Encapsulated endings

Answer 3

Naked nerve endings

• Merkel’s disc. - touch (sustained pressure)
• Meissner’s corpuscle - touch (tap, flutter)
• Ruffini endings - touch (skin stretch, vibration)

Question 4

Pain transmission

• Is by peripheral B fibres.
• Involves cholinergic transmission.
• Is produced by over-stimulation of other receptor types.
• Can be gated by presynaptic inhibition.
• Is via fast C pain fibres.

Answer 4

Can be gated by presynaptic inhibition.

Opioids act on pre- and post-synaptic receptors to inhibit transmission across the synapse in the dorsal horn. Presynaptic decreases calcium influx, inhibiting NT release. Post-synaptic increases K conductance, hyperpolarising the cell. Descending modulatory pathways also act on pre and post-synaptic receptors

• Is by peripheral A delta (thin, myelinated, release glutamate, fast aspect to pain that allows localisation) or C fibres (wide, unmyelinated, glutamate and substance P for slow, dull, intense pain)
• Involves Glutamate and substance P. Descending modulatory pathways use serotonin (nerves from NRM) and catecholamines (nerves from RVM)
• Is produced by specific nociceptors (mechanical, thermal, chemical) that are distinct from other somatosensory receptors
• Is via slow C pain fibres. (all c fibres are slow - unmyelinated)

Question 5

Co-transmitters released with NA include

• VIP and DA
• ATP and neuropeptide Y
• DA and neuropeptide Y
• Tyrosine and ATP
• ACh and VIP

Answer 5

ATP and neuropeptide Y

Question 6

The size of the action potential is decreased by

• Decreasing intracellular Ca
• Increasing external Na
• Decreasing the external Na
• Decreasing the internal K
• Increasing the internal K

Answer 6

Decreasing the external Na

Na is involved in magnitude of AP

K is involved in RMP

Ca is involved in degree of neurotransmitter release and muscle contraction

Cl is inhibitory

Question 7

all of the following ascending sensory pathways are located in the dorsal column except

• pain
• touch
• pressure
• vibration
• proprioception

Answer 7

Pain

Dorsal = light touch, vibration, proprioception, pressure

Ventrolateral spinothalamic = pain, temperature, crude touch

Question 8

concerning the visual pathway

• macular sparing occurs due to the arrangement of fibres in the optic tract
• Brodmann’s area is located in the temporal lobe.
• The optic tract ends in the medial geniculate body.
• The optic disc lies 3mm medial to and slightly above the posterior pole of the globe
• a pituitary tumour often causes a homonymous hemianopia.

Answer 8

The optic disc lies 3mm medial to and slightly above the posterior pole of the globe

macular sparing occurs because macular representation is seperate from that of the peripheral fields and relatively very large.

Brodmanns area is a classification of areas in the brain, not an area itself

The optic tract ends in the lateral geniculate body

a pituitary tumour often causes a bitemporal hemianopia (by compressing the nasal nerve fibres in the optic chiasm).

Question 9

within the sympathetic nervous system

• sweat glands are supplied by β2 receptors.
• activation promotes gluconeogenesis.
• bronchial glandular secretion is inhibited by β2 receptor stimulation
• at the post ganglionic neuron, DA is responsible for the slow excitatory post synaptic potential
• the preganglionic neurons leave the spinal cord in the ventral roots of the thoracolumbar spine

Answer 9

the preganglionic neurons leave the spinal cord in the ventral roots of the thoracolumbar spine

• sweat glands are supplied by alpha 1 receptors.
• activation promotes Glycogenolysis (need to burn fuels)

Need to confirm below

• bronchial glandular secretion is inhibited by β2 receptor stimulation
• at the post ganglionic neuron, DA is responsible for the slow excitatory post synaptic potential

Question 10

In the visual pathway

• Axons of the ganglion cells pass in the optic nerve and optic tract and end in the medial geniculate body of the hypothalamus.
• Fibres of each temporal hemi-retina decussate in the optic chiasm.
• The primary visual receiving area is Brodmann’s area 17
• The fovea contains no cones.
• 80% of input to the geniculate nucleus comes from the retina, the other input is from brain regions involved in feedback regulation.

Answer 10

The primary visual receiving area is Brodmann’s area 17

• Axons of the ganglion cells pass in the optic nerve and optic tract and end in the lateral geniculate body of the hypothalamus.
• Fibres of each nasal hemi-retina decussate in the optic chiasm (but supply the temoral visual fields)
• The fovea contains no rods - very sensitive to colour and acuity, but poor light perception (in the dark, periphary is more able to pick up dim light sources)
• 10-20% of input to the geniculate nucleus comes from the retina, the other input is from brain regions involved in feedback regulation

Question 11

Regarding reflexes

• The reaction time for knee jerk is 0.1s
• Jendrassik’s manoeuvre enhances the knee jerk reflex
• Spindles are located in muscle tendons.
• Afferent neurons carry the impulse to the muscle.
• Muscle spindle fibres are innervated by Ib type nerve.

Answer 11

Jendrassik’s manoeuvre enhances the knee jerk reflex

• The reaction time for knee jerk is 0.015-0.03s (15-30ms)
• Spindles are located in Muscle bellies
• Efferent neurons carry the impulse to the muscle
• Muscle spindle fibres are innervated by Ia type nerve. Golgi tendon organs are innervated by 1b

Question 12

Which of the following is false

• Unilateral transection of the left optic tract causes a right sided homonymous hemianopia
• The fovea contains only cones
• Dark adaption is maximal at around 20 minutes
• Optic nerve fibres from the upper retinal quadrants terminate in the medial half of the lateral geniculate body
• Na channels in rods and cones are open in response to light.

Answer 12

Na channels in rods and cones are Open in absence of light, close in the presence

Photoreceptor cells (rods and cones) produce a stimulus at baseline, in the dark. cGMP-gated Na channels are open in the dark, allowing Na influx into the outer segment. NaKATPase in the inner segment drives this flow. In the light, cGMP breaks down and so the ion channels close, hyperpolarising the cell, and reducing glutamate relase. This reduction in glutamate release is what produces a signal in the bipolar cells.

Question 13

Which is false

• The alpha rhythm is the dominant rhythm seen on EEG of adults
• Corticospinal and corticobulbar system is the primary pathway for the initiation of skilled voluntary movement
• Basal ganglion is composed of the putamen, globus pallidus and substantia nigra
• Flocculonodular lobe is concerned with equilibrium
• Cold receptors respond from 10-38 degrees Celsius

Answer 13

Basal ganglion is composed of the putamen, globus pallidus and substantia nigra - as well as caudate nucleus and subthalamic nucleus

• The alpha rhythm is the dominant rhythm seen on EEG of adults - when awake, resting, eyes closed, at rest. Not when aroused or focussed (then it is gamma oscillations)
• Corticospinal and corticobulbar system is the primary pathway for the initiation of skilled voluntary movement
• Flocculonodular lobe is concerned with equilibrium
• Cold receptors increase firing from 40-24 degrees Celsius, then reduce to nothing at 10c (so do respond from 10-38 degrees)

Question 14

Characteristics of the brain, CSF and cerebral circulation include

• CSF volume of 150mL at a lumbar pressure of 0-100 mm CSF
• CSF/plasma protein ratio of 1, glucose of 0.6
• Weight of 1.4 kg suspended in CSF from the dura mater by arachnoid trabeculae
• Susceptibility to convulsions at normal BSLs in diabetics
• Oxygen consumption of 25mL/min ie 10% total body consumption

Answer 14

Susceptibility to convulsions at normal BSLs in diabetics

Question 15

Regarding the ANS

• Does not have a reflex arc like somatic nervous system.
• Has DA as the main neurotransmitter.
• Has cholinergic division which increases activity of intestinal musculature and increases gastric secretion
• Neurotransmitter NA is metabolized by pseudocholinesterase.
• Is not involved in visceral sensation.

Answer 15

Has cholinergic division which increases activity of intestinal musculature and increases gastric secretion

• Can have a reflex arc like somatic nervous system eg Pupillary reflex
• Has ACh and Na as the main neurotransmitters
• Neurotransmitter NA is metabolized by COMT and MAO
• Carries most visceral sensation.

Question 16

which is not synthesised in postganglionic sympathetic neurons

• L-dopa
• DA
• NA
• A
• ACh

Answer 16

Adrenaline

Question 17

In the ANS β agonism results in

• Constriction of the renal vasculature
• Decreased velocity of conduction in the AV node
• Decreased velocity of conduction in the His/Pukinje system
• Decreased ventricular contractility
• Increased insulin and glucagons secetion

Answer 17

Increased insulin and glucagons secetion

• Dilation of the renal vasculature
• Increased velocity of conduction in the AV node
• Increased velocity of conduction in the His/Pukinje system
• Increased ventricular contractility

ie Beta agonism does the opposite of what beta blockers do

Question 18

The reticular activating system

• Has depressed conduction during anaesthesia
• Is located in the pons
• Is a simple collection of parallel nerve fibres
• Has no input from cranial nerves
• Is electrically isolated from the cortex

Answer 18

Has depressed conduction during anaesthesia

• Is located in medulla and midbrain*
• is a complex polysynaptic network*
• Has converging inputs from sensory and cranial nerves*
• Increases cortical electrical activity*

Question 19

the most sensitive part of the eye is the

• optic disc
• fovea centralis
• area with maximal rods

Answer 19

Fovea

As it has the highest concentration of cones which all synapse on a single bipolar cell which then go to a single ganglion cell. (Each foveal cell is individually mapped in the visual cortex - I’m pretty sure)

Is thin because it has pushed all its inner cell layer and shit to the side to give greater VA with less stuff blocking the lights path

The optic disk is the optic nerve / blindspot

Rods give light sensitivity but no acuity

Question 20

regarding CSF

• composition is essentially the same as brain ECF
• CSF production ~ 150mL/d
• Higher concentration of K with respect to plasma
• Higher concentration of protein

Answer 20

No clear answer is correct

• CSF is produced in two steps. First, a transudate forms in the choroid plexus due to hydrostatic pressure. Then active transport of Na, K, and Cl through endothelial cells draws water and CO2 osmotically across the tight junctions.
• Production ~600-700ml/day, about 125ml present at any one time
• CSF has a higher concentration of Na and Cl than plasma, but less K, Ca, glucose, protein

Question 21

which penetrates the CSF fastest

• H2O, CO2, O2
• CO2, O2, N2O

Answer 21

H2O, CO2, O2

Question 22

anterolateral dissection of the spinal cord is associated with

• ipsilateral loss of pain
• ipsilateral loss of temperature
• ipsilateral hyperreflexia.
• contralateral vibration loss
• none of the above.

Answer 22

Nick believes c) but had originally been told none of the above

Anterolateral or ventrolateral spinothalamic tract carries pain, temperature, crude touch, tracts to cerebellum

These decussate immediately

Therefore dissection will cause contralateral pain and temperature loss

Will also damage ventral corticospinal tract (direct, has interneurons etc, 20% of fibres), tectospinal, recticulospinal, and vestibulospinal tracts.

Degree of damage would determine if lateral corticospinal tract was damaged, but this should give ipsilateral UMN lesion, ie involve hyperreflexia.

Dorsal column carries light touch, vibration, proprioception

These decussate in medulla

Even if cut in the question, would provide ipsilateral vibration loss

Question 23

The sensation for cold

• Is relayed by the thalamus
• Is transmitted by the dorsal columns. Anterolateral spinothalamic tract
• Is an uncrossed sensory modality
• Is mediated by substance P fibres
• Is mediated by A α fibres

Answer 23

Is relayed by the thalamus

Is transmitted by the anterolateral spinothalamic tract

Decussates immediately

Is mediated by A delta and C fibres

(warm is just C)

Substance P is involved in dull aching pain

Question 24

1 Regarding muscle spindles:

• a) are composed of extrafusal fibres
• b) receive δ efferents
• c) all subtypes send afferents via “flower spray” ended 1a nerves
• d) nuclear chain fibres show dynamic response
• e) afferent discharge decreased with muscle stretch

Answer 24

b) Receive delta efferents

Are composed of intrafusal fibres (extrafusal is all the other muscle cells in the muscle)

Afferent discharge is increased with muscle stretch

Question 25

2 Regarding the dorsal column: * a) carries ipsilateral pain and temperature * b) ascends to the nuclei gracillis and cuneate * c) receives efferents from contralateral stimuli * d) sacral efferents lie laterally * e) runs anteriorly in the cord

Answer 25

b) ascends to the nuclei gracillis and cuneate Dorsal column carries ipsilateral touch, proprioception, vibration, and thus receives efferent from ipsilateral stimuli. Arranged anatomically, so the sacral nerves are most medial, and cervical most lateral As its name suggests, it runs dorsally. *Anterolateral spinothalamic* carries contralateral pain and temperature

Question 26

3 Temperature sensation: * a) respond to compartitive temp gradient ??? skin * b) cold receptors predominate * c) warm receptors respond 30° - 100° * d) afferents carried via the dorsal column * e) warm and cold afferents carried via Adelta fibre

Answer 26

**Cold receptors predominate (4-10x as many as warm)** Afferents carried in anterolateral spinothalamic columns (along with pain) Warm receptors respond via C fibres from 30-46 degrees (after which nociceptors take over) (Cold receptors are carried via C and Adelta fibres, fire increasing from 40-24 degrees, then reduce to 10c)

Question 27

4 Regarding visual receptors: * a) rods predominate in the fovea * b) rhodopsin is the primary pigment of rods * c) lie anterior (superficial) to their neural pathway * d) colour blindness is an autosomal recessive gene * e) supplied by retinal vessels

Answer 27

**Rhodopsin is the primary pigment of rods** **(made up of retinal [Vit. A aldehyde] and opsin)** Rods and cones get their nutrient supply from the choroid plexus Lie *behind* their neural pathway (ie the light mist pass through the bipolar cells and nerve fibres before it gets to the photoreceptors) Colour blindness is autosomal *dominant* *Cones* predominate in the fovea

Question 28

5 Regarding sound and hearing: * a) high pitched sounds are detected at the apex of the cochlear * b) Hair cells are bathed in endolymph * c) detected by hair cells found within the tectorium membrane * d) 95% of afferent neurones → outer hair cells * e) ???????

Answer 28

**Apparently the answer is ‘e) ??????’** **I’m sure it is b). Gangongs is confusing, but seems to imply hair cells are bathed in endolymph, which is high in K+, and this helps to generate the K+ influx needed to generate a potential. Could be both, I don’t know.** High pitched sounds are detected at the base, low pitch sounds at the apex There are 20,000 outer hair cells, 3500 inner hair cells. 90-95% afferent neurons supply inner hair cells. On the other hand, most efferent nerves supply the outer hair cells. Tectorial membrane has the tips of outer hair cells embedded in it.

Question 29

6 Regarding noradrenergic stimulation: * a) miosis occurs * b) increases blood flow to the skin * c) increases thresholds in the reticular formation * d) causes erection in males * e) elevates free fatty acid levels

Answer 29

Answer listed as D) but this is wrong. I think it is e) elevates FFA levels. Norad = sympathetic B3 → lipolysis + A1/B2 → glycogenolysis (likely increases FFA) * Mydriasis* occurs (pupil dilation; cholinergics cause miosis) * Sympathetic ACh* release causes increased blood flow to skin/skeletal muscles (along with sweat glands are the two sympathetic ACh uses) Parasympathetic causes erection, sympathetic causes ejaculation Clarify if RAS activation or deactivation causes sleep

Question 30

7 Regarding cholinergic stimulation: * a) causes amylase secretion from salivary glands * b) decreases secretion from pancreatic acini cells * c) relaxes the gallbladder * d) has no effect on renal arterioles * e) relaxes bronchial smooth muscle

Answer 30

**d) has no effect on renal arterioles** Parasympathetic has no effect on any arteriole or vein (or skin for that matter) Causes *contraction* of the GB *Constricts* bronchial smooth muscle Causes a *profuse watery salivary secretion*, whereas a1 or B (sympathetic) causes a thick, viscous secretion with amylase Increases panceatic acini cell secretion (digestion), but has no effect on Islet cells (insulin - this is mediated by a2 and B2)

Question 31

The emotional component to pain is due to activation of: * a) post central gyrus * b) sylvian fissure * c) hippocampus * d) cingulated cortex * e) calcavine fissure

Answer 31

a) post central gyrus

Question 32

The chemical agent that initiates impulses in pain fibres is: * a) ATP * b) substanceP * c) Ca2+ * d) H+ * e) K+

Answer 32

b) substance P Along with glutamate

Question 33

Regarding thermoceptors: * a) there are more warm receptors than cold receptors * b) cold receptors respond to 10-38°C * c) afferents for cold receptors are C fibres only * d) afferents found in the ventral spinothalamic tract * e) respond to the temperature gradient across the skin

Answer 33

**b) cold receptors respond to 10-38°C** * ~40→ 10c, increase firing then they decrease towards 10* * 4-10x as many cold as warm* * Warm respond 25→45* Afferents for cold are C and Adelta (warm is C only) Afferents are in the Lateral spinothalamic tract (crude touch and pressure are ventral)

Question 34

Regarding body temperature: * a) humans are poikilothermic * b) oral temperature is usually higher than rectal temperature * c) it is usually lowest at 6am * d) children have more precise temperature regulation * e) emotion has no effect on core temperature

Answer 34

* c) it is usually lowest at 6am (and highest in the evenings) * Poikilothermic = cold blooded. Humans are homeothermic * Oral temp ~0.5c lower than rectal * Temp control is less precise in children, they often run 0.5c hotter than adults. * Rises slightly during emotional excitement (likely due to unconscious tensing of muscles)

Question 35

Regarding the hypothalamus: * a) it has neural connections with the anterior pituitary gland * b) it integrates the vomiting reflex * c) the anterior hypothalamus responds to cold * d) it controls circadian rhythms via the supraoptic nuclei * e) it has osmoreceptors in the anterior hypothalamus to stimulate thirst and vasopressin release

Answer 35

Answer given as b) vomiting reflex, but this is in the Medulla Unsure if C or E Anterior hypothalamus does have temperature receptors, but the posterior hypothalamus is involved in systemic response to cold, anterior to heat. Regarding osmoreceptors: *Osmoreceptors in the anterior hypothalamus stimulate thirst, and vasopressin is released from the posterior pituitary in response to osmoreceptors which may or may not be the same as those involved in thirst. Also notes multiple other locations it can be secreted from. (This answer could also be correct)* It has neural connections with the posterior pituitary, but only a portal blood supply to the anterior Circadian rhythm seems to be controlled by the pineal gland and thalamus

Question 36

26 When a visual stimulus falls on a given point in the retina for a long time: * a) the image becomes more clearly focused * b) there is adaptation in the visual cortex * c) the discharge rate in the bipolar cells increases * d) the pupils constrict * e) the image fades and disappears

Answer 36

They think A) image becomes more focussed. Lateral inhibition (inhibition of nearby neural units if one is activated) helps sharpen the edges of an object (or any sensation). It is not clear that this occurs only if the stimulus is there for a long time or any time. I can’t find anything else in Ganongs to point me further.

Question 37

Regarding the vomiting reflex, which is INCORRECT? * a) it is integrated by the medulla * b) breath is held in expiration * c) the glottis closes * d) it involves salivation * e) there are afferents from vestibular nuclei

Answer 37

b) breath is held in *mid-inspiration* Starts with salivation and nausea, reverse peristalsis moves small intestine contents → stomach, glottis closes, breath held. Abdominal muscles contract and sphincters loosen. Integrated by the medulla. Motion/vertigo → labyrinth→ cerebellum→ vomiting centre (also pain, sights, anticipation, pharyngeal stimuatlion, gastric irritants, drugs acting on vomiting centre itself eg opioids or chemotherapy)

Question 38

Herring bodies are: * a) nuclei of the hypothalamus * b) secretory granules in the posterior pituitary * c) circumventricular organs * d) neurons connecting vestibular nuclei with the vomiting centre * e) vesicles containing ACTH, TSH, GH, FSH, CH and PRL

Answer 38

b) secretory granules in the posterior pituitary Herring bodies or neurosecretory bodies are structures found in the posterior pituitary. They represent the terminal end of the axons from the hypothalamus, and hormones are temporarily stored in these locations. They are neurosecretory terminals. (they thought c); most answers they give in this section are wrong)

Question 39

15 The neurotransmitter secreted by primary afferent fibres for severe pain is: * a) glutamate * b) acetylcholine * c) substance P * d) opioid peptides * e) noradrenaline

Answer 39

Answer given is d) opioid receptors but this is clearly wrong (endogenous opioids modulate pain response - are not involved in the primary afferent). I would guess the answer is A (but C partially correct too) Acute pain is transmitted by Adelta fibres and uses glutamate as its transmitter for speed. Substance P is used in C fibres (along with glutamate) to transmit deep, visceral pain (which Ganongs notes can be severe).

Question 40

Regarding rods and cones: * a) Na+ channels are closed in the dark * b) light striking the outer segments results in a depolarising receptor potential * c) the receptor potentials are all-or-nothing * d) rhodopsin is a serpentine receptor * e) acetylcholine is released from the synaptic terminal

Answer 40

b) Light striking the *outer* segment causes a depolarising receptor potential (as in towards the outside of the eye, cf inner which are closer to the inside; remember the backwards arrangement of neurons in the eye) Na channels are open in the dark, inhibited by light. Rods and cones give varying degrees of EPSP/IPSP - not all or nothing Rhodopsin is a photosensitive pigment in rods Synaptic transmitter is Glutamate (not ACh)

Question 41

17 The visual cortex is situated at the: * a) parieto-occipital sulcus * b) cuneus * c) calcarine fissure * d) lateral geniculate body * e) angulargyrus

Answer 41

Primary visual cortex (aka Brodmanns area 17) is located in the occipital lobe around the calcarine fissure (C is the answer) Lateral geniculate body in the thalamus is the end of the ganglion cells/optic nerve/optic tract. Tract between LGB and PVC is called the geniculocalcarine tract (as an aside, the answer given here was d) - whoever wrote this section is a dipshit, most answers are wrong)

Question 42

18 In the visual pathway: * a) the lateral geniculate bodies are made up of t layers * b) fibres for reflex pupillary constriction leave the optic nerve at the optic chiasm * c) pituitary tumours can cause homonymous hemianopia * d) macular sparing may or may not occur with lesions in the geniculocalcanine tract * e) binasal visual field fibres decussate at the opticchiasm

Answer 42

D) macular sparing may occur - *the macular fibres separate from the peripheral fibres in the LGB and run a seperate tract, and are located in a seperate area on the visual cortex. The macula also occupies relatively much more of the neurons and primary visual cortex, thus an injury must cover a very large area to knock it all out.* LGB is made up of 6 layers (1-2=magnocellular, 3-6=parvocellular). Don’t know where the fuck T came from. Reflex pupillary constriction is a reflex arc - afferents come from the optic nerve (II), efferents come from the Occulomotor nerve (III) Pituitary tumours can cause a bitemporal hemianopia. Lesions in optic tract cause a homonymous hemianopia Bitemporal visual fields decussate at the optic chiasm (received by the nasal regions of the retina though)

Question 43

19 When a normal innervated skeletal muscle is stretched, the initial response is contraction, but with increasing stretch, the muscle suddenly relaxes because: * a) with strong stretch, the efferent discharge is decreased * b) with strong stretch, the discharge from the annulospiral endings of afferent nerve fibres is inhibited * c) with strong stretch, there is decreased activity in the afferent nerve fibres from the Golgi tendon organs * d) with strong stretch, there is increased activity in the afferent nerve fibres from the Golgi tendon organs * e) because of reciprocal innervation, there is increased discharge in the afferent nerve fibres from the antagonists to the stretched muscle

Answer 43

d) with strong stretch, there is *increased activity* in the afferent nerve fibres from the *Golgi tendon organs* * Inverse Stretch reflex:* Golgi tendon organs mediate contraction strength of a muscle, much as muscle spindles mediate muscle length. Have an inhibitory response on muscle contraction. They are in series with muscle (unlike spindles which are in parallel); the muscle takes up most passive stretch as it is more elastic, but if it is stretched too much, they will fire and relaxation occurs.

Question 44

20 With regard to spinal tracts, which is INCORRECT? * a) lateral corticospinal fibres decussate in the pyramids of the medulla * b) ventral corticospinal fibres decussate at the level of synapse in spinal cord * c) dorsal column fibres synapse in gracile and cuneate nuclei with decussating * d) lateral spinothalamic tract carries pain and temperature fibres * e) ventral spinothalamic tract decussates at the medial lemniscus

Answer 44

e) ventral spinothalamic tract decussates at the medial lemniscus * Both spinothalmaic tracts decussate in the spinal cord in the anterior white commissure.* * Lateral spinothalamic carries pain and temp* * Ventral spinothalamic carries crude touch and pressure* Dorsal column fibres synapse in gracile and cuneate nuclei of medulla, before decussating and ascending the medial lemniscus

Question 45

In a polysynaptic reflex, which of the following happen when the strength of the adequate stimulus is increased? * a) the amplitude of the motor response is increased * b) the motor response spreads to include other muscles and even other limbs * c) there is increased inhibition of stretch reflexes * d) the duration of the motor response increases * e) all of the above are true

Answer 45

They thought A, I reckon E) all of the above. The withdrawal reflex is an example of a polysynaptic reflex. Weak noxious stimuli produce a weak flexion response (eg lifting a foot). Stronger stimuli produce a larger response (lift the foot higher), more prolonged response, stretch reflex is inhibited (eg the knee is flexed in withdrawal - the extension of the patellar reflex is inhibited), and can also spread to other muscle groups as part of the crossed extensor response which ensures you don’t fall over when this happens.

Question 46

22 A tumour causing external compression to the anterior cervical spinal cord would be expected to: * a) impair pressure and pain sensation mostly from sacral and lumbar areas * b) impair fine touch and vibration mostly from sacral and lumbar areas * c) impair pain only from cervical areas * d) impair vibration sense only from cervical areas * e) impair joint position from sacral areas only

Answer 46

They thought D, I think: * c) impair pain only from cervical areas The spinothalamic tracts decussate in the anterior white commissure and so would be vulnerable at the level they decussate - ie cervical spinothalamic tracts. Pain and pressure - lateral spinothalamic tract Fine touch, vibration, proprioception - dorsal columns None of these fibres run anteriorly (crude touch and pressure in the ventral spinothalamic tract is the only sensory column that could be affected (Motorwise the ventral corticospinal runs anteriorly [carries 20% of motor efferents]; also the tectospinal, vestibulospinal, and various other specialised motor tracts).

Question 47

23 Which of the following need to be intact for normal stereognosis: * a) dorsal columns * b) parietal lobe * c) pressure pathways * d) all of the above * e) noneoftheabove

Answer 47

Stereognosis is the ability to perceive the form and nature of an object without looking at it (eg keys or a nice hat). This requires intact touch and pressure sensation, and thus an intact dorsal column. Answer is all of the above, as it needs a dorsal column and pressure pathway, as well as an intact primary sensory cortex. Tactile agnosia is the absence of this, and can be due to damage to dorsal column, cerebral cortex, or primary sensory cortex.

Question 48

24 Bitemporal hemianopia is most likely to be caused by a lesion at the: * a) optic nerve * b) optic chiasm * c) optic tract * d) optic radiation * e) visual cortex

Answer 48

Optic chasm

Question 49

25 Regarding temperature regulation, which is NOT true? * a) the anterior hypothalamus contains temperature sensitive cells * b) shivering is activated by the posterior hypothalamus * c) the anterior hypothalamus controls mechanisms activated by heat * d) horripilation acts to increase heat production * e) fever is produced by the action of cytokines on the hypothalmus

Answer 49

e) fever is produced by the action of cytokines on the hypothalamus. **Bacterial toxins → make macrocytes, monophages, and Kupffer cells to produce cytokines that act as endogenous pyrogens** **Eg IL-1B, IL-6, TNF-a, IFN** **However these cytokines are too large to cross the BBB, so act indirectly on the hypothalamus via OVLT.** Anterior hypothalamus itself has temp sensitive cells, along with inputs (primarily cold receptors) from skin, spinal cord, deep tissue, and extra thalamic portions of the brain. Responses to cold are mediated by the posterior hypothalamus, responses to heat by the anterior hypothalamus.

Question 50

27 Which of the following affect visual activity? * a) cataracts * b) vitamin A deficiency * c) astigmatism * d) contrast between stimulus and background * e) all of the above

Answer 50

e) all of the above

Question 51

28 The ‘tympanic reflex’: * a) is activated by foreign bodies in the external auditory canal * b) results in vertigo * c) is activated by high-pitched sounds only * d) results in the decreased transmission of sound * e) noneoftheabove

Answer 51

d) results in the decreased transmission of sound Tympanic reflex = contraction of tensor tympani and stapedius, which causes reduced sound transmission to prevent strong sound waves excessively stimulating the auditory receptors.

Question 52

29 If one leg is immersed in ice water, the subject’s immediate response(s) include: * a) generalised vasoconstriction * b) increased secretion of adrenaline * c) shivering * d) all of the above * e) noneoftheabove

Answer 52

They think ‘?’ Cold causes shivering and catecholamine release, and localised cutaneous vasoconstriction. ‘Generalised vasoconstriction’ seems to be wrong Shivering and adrenaline release can occur in cold, but unsure if these happen ‘immediately’, or if just the one leg is placed in water. If generalised vasoconstriction does not occur, I don’t know which of the other two, if either, occurs first or immediately.

Question 53

30 Regarding pain transmission, which is NOT true? * a) ‘fast pain’ fibres are Aδ fibres * b) ‘slow pain’ fibres are C fibres * c) substance P is the central transmitter * d) all impulses pass through the central horn * e) pain sensation results from over-stimulation of other sensory modalities

Answer 53

e) pain sensation results from stimulation of specific nociceptors (generally naked nerve endings)

Question 54

31 Which is NOT a part of the basal ganglia? * a) caudate nucleus * b) cuneate nucleus * c) substantia nigra * d) putamen * e) globus pallidum

Answer 54

b) → the old cunt eater nucleus. But seriously the answer is B. Basal ganglia are the caudate nucleus, putamen, substantia nigra, globus pallidum, and subthalamic nucleus Caudate nucleus + putamen = striatum Globus palladus + putamen = lenticular nucleus

Question 55

32 With regard to pain pathways, all the following are true EXCEPT: * a) peripheral afferents are transmitted along A (delta) and C fibres * b) an intact cerebral cortex is necessary for pain sensation * c) the synaptic transmitter released by primary afferent fibres subserving pain is substance P * d) afferent fibres subserving pain sensation from viscera reach the CNS by both sympathetic and parasympathetic pathways * e) the sensory organs for pain are marked nerve endings

Answer 55

a, d, e are all correct. c) both *glutamate* and substance P I believe are released by primary pain afferents. b) - they think this is right (as in incorrect), I cannot find the answer to this, but Ganongs references the pain pathway being somatic and visceral pain fibres converging on the same second order neuron in dorsal horn → thalamus → somatosensory cortex (under referred pain section) So c) could be right because both are released not just substance P Or b) if they mean pain sensation can occur without a cortex, but it cannot be interpreted. In an exam, I would put c. Correct me if you have more information.

Question 56

33 Cerebellar disease in humans causes all of the following EXCEPT: * a) dysmetria * b) scanning speech * c) lead pipe rigidity * d) rebound phenomenon * e) dysdiadockokinesia

Answer 56

Scanning speech = slurred speech Rebound phenomenon = inability to check forearm flexion if resistance is suddenly removed (eg the arm will go flying backwards). Occurs as they are not able to stop the limb movement. This also ties into dyskiadokinesis. Dyskiadokinesis = inability to perform rapidly alternating movementes Dysmetria = past pointing (and the overcorrection is intention tremor) Lead pipe rigidity occurs in Parkinsons (as can cogwheel rigidity - cf give-way spasticity seen in UMN lesions)

Question 57

The righting reflex is pronounced after sectioning of the neural axis above which level: * a) spinal cord * b) medulla * c) mid-brain * d) subcortical nuclei * e) all above intact but decerebellate

Answer 57

Aka labyrinth righting reflex They think c) midbrain This is a brainstem reflex so must be high up - either medulla, mid-brain, or subcortical nuclei. Ganongs 23rd states ‘a series of responses integrated for the most part in the nuclei of the midbrain’, this is left out of the 26th ed. No mention of the pathology of them though. Not sure what they mean by ‘pronounced’. Exaggerated in a lesion?

Question 58

35 Regarding muscle spindles, which is NOT true? * a) they contain nuclear bag and nuclear chain fibres * b) they receive a motor supply via Aγ fibres * c) they discharge more upon stretching of the muscle * d) they are responsible for the inverse stretch reflex * e) they relay information to the cord via Ia fibres

Answer 58

d) they are responsible for the inverse stretch reflex This is mediated by Golgi tendon organs.

Question 59

1 The action potential of a neuron (influx): * a) is initiated by efflux of Na+ * b) is terminated by efflux of K+ * c) declines in amplitude as it moves along the axon * d) results in transient reversal of the concentration gradient of Na+ * across the cell membrane * e) is not associated with any net movement of Na+ of K+ across the cell membrane

Answer 59

b) is terminated by efflux of K+ They think e) * a) is initiated by *influx* of Na+ * c) declines in amplitude as it moves along the axon *- pretty sure this does not occur* * d) results in transient reversal of the *electrical gradient* of Na+ across the cell membrane *(but not concentration)* * e) is definitely associated with net movement of Na+ of K+ across the cell membrane (both in terms of concentration and electrical gradients)

Question 60

2 The functions of tropomyosin in skeletal muscle include: * a) releasing Ca2+ after an action potential * b) sliding on actin to produce shortening * c) binding to myosin during contraction * d) acting as a “relaxing protein” at rest by covering up the sites where myosin binds to actin * e) generating ATP which passes to the contractile mechanism

Answer 60

d) acting as a “relaxing protein” at rest by covering up the sites where myosin binds to actin - along with Troponin I * a) releasing Ca2+ after an action potential - Troponin C * b) sliding on actin to produce shortening - Myosin * c) binding to myosin during contraction - ATP or myosin * e) generating ATP which passes to the contractile mechanism - heads of Myosin

Question 61

3 Regarding the autonomic nervous system: * a) it does not have a reflex arch like the somatic nervous system * b) it has dopamine as the main transmitter * c) it has cholinergic division which increases activity of the intestinal musculature and increases gastric excretion * d) neurotransmitter noradrenaline is metabolised by pseudocholinesterase * e) it is not involved with visceral sensation

Answer 61

c) it has a cholinergic division… Acts on muscarinic receptors. GPCRs, 5 subtypes. Found in autonomic receptors of parasympathetic activity ( SA node, AV node, smooth muscle) and also in autonomic ganglia where it produces slow EPSP (in contrast to the fast EPSPs produced by Nn receptors). M2+3 are the ones on most target autonomic organs. Compare to nicotinic receptors: Nn is found in autonomic ganglia (receptors on post-ganglionic cells, ACh released by preganglionic; Nm is found at the NMJ) Noradrenaline is metabolised by COMT and MAO

Question 62

4 Which of the following does NOT act via an intracellular receptor? * a) atrial natriuretic peptide * b) cortisol * c) thyroxine * d) aldosterone * e) retinoic acid

Answer 62

Intracellular receptors are generally acted on by steroid derivatives (lipid-derived so can cross cell membranes). Cortiasol, thyroxine, aldosterone are all steroid-derived. Retinoic acid mediates Vit A action by binding to DNA receptors ANP is mediated by cell-surface receptors

Question 63

5 Which of the following phosphate compounds is MOST important in the production of energy? * a) AMP (adenosinemonophosphate) * b) ADP(adenosinediphosphate) * c) ATP (adenosine triphosphate) * d) GTP(guanosinetriphosphate) * e) CTP(cytidinetriphosphate)

Answer 63

Absolute gimme of a question. Not even going to bother putting the answer here. You know you got it right.

Question 64

6 Steps involved in skeletal muscle contraction include all of the following EXCEPT: * a) binding of acetylcholine to nicotinic receptors * b) increased Na+ and K+ conductance in end plate membrane * c) spread of depolarisation along T tubules * d) binding of calcium to troponin T, with uncovering of its actin-myosin binding site

Answer 64

d) binding of calcium to troponin T, with uncovering of its actin-myosin binding site Binds to Troponin C Easy way to remember - Troponin **C = Calcium** binding Troponin **I = Inhibits** myosin binding (by covering the actin site) Troponin **T = Tropomyosin** binding

Question 65

7 Regarding the resting membrane potential in peripheral nerves: * a) membrane permeability of potassium ions via K+ leak channels produces the resting potential * b) a decrease in extracellular Ca2+ decreases excitability * c) decreasing external Na+ concentration lowers the resting membrane potential * d) changing the external Na+ concentration has no effect on the action potential * e) decreasing the external K+ concentration increases the resting membrane potential

Answer 65

a) membrane permeability of potassium ions via K+ leak channels produces the resting potential Increasing extracellular Ca reduces excitability (its why we give it in hyperkalaemia as a membrane stabiliser) Na does not affect the RMP, only the magnitude of the AP Reducing external K+ reduces the RMP, hyperpolarising the cell and making it less excitable (flat t-waves in hypokalaemia on ECG as T waves correspond to repolarisation)

Question 66

8 Regarding excitation-contraction coupling in skeletal muscle, which statement is INCORRECT? * a) calcium ions bind to troponin T * b) troponin I – tropomyosin complex constitutes a “relaxing protein” * c) each cycle of attachment and detachment shortens muscle length by about 1% * d) ATP is the immediate source of energy * e) globular head of myosin – II possesses actin binding site

Answer 66

a) calcium ions bind to troponin T Troponin C bind Ca

Question 67

9 Microglia: * a) are involved with myelin production * b) are scavenger cells * c) are performed in the brain * d) are important in GABA uptake * e) induce capillaries to form tight junctions and thus the blood brain barrier

Answer 67

b) are scavenger cells They resemble macrophages Macroglia have 3 types: Oligodendrocytes - involved in myelin production in CNS Schwann cells - myelin in PNS Astrocytes - 2 types, both induce capillaries to form the tight junctions for the BBB

Question 68

10 The action potential: * a) is always monophasic * b) has an absolute refractory period lasting to the start of the after depolarisation * c) has a relative refractory period lasting until repolarisation is complete * d) requires opening of voltage gated Na+ channels * e) results in ↓ K+ conductance

Answer 68

d) requires opening of voltage gated Na+ channels The answer so simple its off-putting

Question 69

11 Which of the following nerve fibre types is MOST sensitive to hypoxia? * a) A-alpha * b) A-beta * c) A-delta * d) B * e) C

Answer 69

d) B cells C fibres are most sensitive to local anaesthetics Larger diameter fibres are most sensitive to pressure, so Aa \> Ab \> Ay \> Ad \> B \> C

Question 70

12 Regarding smooth muscle contractility, which statement is INCORRECT? * a) increased by acetylcholine * b) decreased by activation of phospholipase C * c) increased by cold * d) decreased by cAMP * e) increased by stretch

Answer 70

b) is incorrect. Phospholipase C *increases* contractility ACh → PLC → IP3 → increased Ca → increased contractility. Cold and stretch also increase it. cAMP seems to often be associated with adrenergic receptors, and these decrease smooth muscle contractility

Question 71

13 Regarding smooth muscle, which statement is INCORRECT? * a) multi-unit smooth muscle is present in the jejunum * b) may exhibit pacemaker potentials * c) mechanical response is much slower than striated muscle * d) the membrane potential is unstable * e) functions as a syncytium in viscera

Answer 71

a) multi-unit smooth muscle is found in things like the iris muscles that require fine control

Question 72

14 A sarcomere: * a) contains two separate halves of an A-band and an I-band * b) is the space between two A-bands * c) is between two Z-lines * d) has the T-system of the sarcotubular system at sarcomere junctions * e) contracts when the troponin molecule binds to the myosin head

Answer 72

c) is between two Z-lines

Question 73

15 Type I muscle fibres: * a) have fast glycolytic rates * b) have low oxidative capacity * c) are more commonly found in muscle that performs explosive work * d) do not have a very high glycolytic capacity * e) are not abundant in endurance athletes

Answer 73

d) do not have a very high glycolytic capacity Type I = slow oxidative (red) IIa = fast oxidative glycolytic (red) IIb = fast glycolytic (white) Type I is not good for explosive work, but due to high oxidative capacity it has good endurance. IIb is able to quickly access energy stores so is good for explosive movements, but has a low oxidative metabolism so needs to rest and recuperate to keep working once its energy stores are used.

Question 74

16 Regarding cardiac muscle, which statement is INCORRECT? * a) resting membrane potential is about -90mV * b) energy source at rest is mainly fat * c) mechanical response lasts about twice as long as electrical response * d) tetanus cannot occur * e) it has an all-or-nothing contractile response

Answer 74

c) mechanical response lasts about 1.5x as long as electrical response

Question 75

17 Regarding denervation: * a) it causes skeletal muscle hypertrophy * b) does not lead to fibrillation * c) causes hyposensitivity to acetylcholine in skeletal muscle * d) smooth muscle is able to contract if it occurs in vivo * e) causes fasciculations

Answer 75

d) smooth muscle is able to contract if it occurs in vivo Tonus of SM means it shows continuous, irregular contractions independent of its nerve supply Denervation will cause atrophy and ACh hypersensitivity to circulating ACh in skeletal muscle, which causes fibrillations (this hypersensitivity is classic of LMN lesions; NOT fasciculations)

Question 76

18 Which of the following nerve fibre types is MOST sensitive to pressure? * a) A-beta * b) A-gamma * c) A-delta * d) B * e) C

Answer 76

a) A-beta C fibres are most sensitive to local anaesthetics Larger diameter fibres are most sensitive to pressure, so Aa \> Ab \> Ay \> Ad \> B \> C B cells are most sensitive to hypoxia

Question 77

19 Regarding decerebration: * a) decerebration produces spinal shock * b) decerebrate rigidity is spasticity due to diffuse facilitation of stretch reflex * c) there is increased rate of discharge in the α afferent neurons * d) spasticity produced by decerebration is more marked in flexor muscles * e) most commonly produces upper limb flexion and lower limb extension

Answer 77

b) decerebrate rigidity is spasticity due to diffuse facilitation of stretch reflex Decerebrate = extension upper and lower limbs (excl. wrists and fingers) Decorticate = upper limb flexion, lower limb extension

Question 78

20 Which of the following nerve fibre types has the LARGEST diameter? * a) C * b) A-alpha * c) B * d) A-gamma * e) A-beta

Answer 78

b) A-alpha

Question 79

21 The following are NOT energy sources of muscle: * a) phosphorylcreatine * b) fattyacids * c) glucose * d) glycogen * e) creatine

Answer 79

e) creatine Creatine is phosphorylated to produce phosphorylcreatine, which is an energy source. Creatine is to phosphorylcreatine what ADP is to ATP

Question 80

22 Regarding sensory organ stimulation, which statement is INCORRECT? * a) adaptation occurs over the temperature range 20-40°C * b) pain is sensed by naked nerve endings * c) pacinian corpuscles are rapidly adapting touch-pressure receptors * d) naked nerve endings can detect all four cutaneous sensory modalities * e) any given nerve ending can signal more than one sensory modality

Answer 80

e) any given nerve ending can signal more than one sensory modality They are specialised for one purpose (or at least signal to the brain one type of stimuli)

Question 81

23 Regarding neurotransmitters, which of the following is INCORRECT? * a) glutamate is excitatory * b) GABA is inhibitory at presynaptic neurons * c) glycine is excitatory at postsynaptic neurons * d) GHB (gamma hydroxybutyrate) is inhibitory * e) aspartate is excitatory

Answer 81

c) glycine is excitatory at postsynaptic neurons GABA and glycine are inhibitory towards post-synaptic neurons.

Question 82

24 The stretch reflex: * a) is classically initiated by tapping on the quadriceps muscle * b) is initiated by stretch of the muscle * c) involves impulses being conducted from the muscle spindle to the motor cortex * d) involves extrafusal fibres stimulating annulospiral and flowerspray sensory fibres * e) involves gamma afferents of leksell

Answer 82

b) is initiated by stretch of the muscle Hence the name.

Question 83

25 Which of the following is NOT present in smooth muscle cells? * a) actin * b) myosin-II * c) tropomyosin * d) almodulin * e) troponin

Answer 83

e) troponin Utilise a ?calmodulin- myosin light chain kinase complex instead

Question 84

26 Regarding the structure of cardiac muscle, which statement is INCORRECT? * a) T-system lies at Z-lines * b) functions as a syncytium due to the presence of tight junctions * c) intercalated discs occur at Z-lines * d) contains large numbers of elongated mitochondria * e) thin filaments include troponin T, C and I

Answer 84

b) functions as a syncytium due to the presence of *gap junctions*

Question 85

27 Regarding the cardiac muscle action potential, which statement is INCORRECT? * a) sodium ions enter via “fast” channels in phase 0 * b) chloride ions may enter cell during phase 1 * c) sodium ions enter via “slow” channels in phase 2 * d) relative refractory period ends in phase 3 * e) class I anti-arrhythmics reduce the slope of phase 4

Answer 85

**d) relative refractory period ends in phase *4*** * ARP ends in phase 3, RRP ends in phase 4* * Older texts seem to have mentioned chloride fluxes in APs, however current Ganongs does not mention these at all - just Na, K, and Ca.* * Phase 0 = rapid Na influx* * Phase 1 = closure of fast Na channels* * Phase 2 = plateau, calcium influx + K efflux* * Phase 3 = repolarisation = K efflux* * Phase 4 = RMP* Class I anti-arrhythmics are Na-channel blockers (eg procainamide, lidocain, phenytoin, flecainide) and they affect phase 0 (Na influx)

Question 86

28 Which of the following nerve fibre types represents the efferent limb of the muscle spindle reflex arc? * a) A-alph * b) A-beta * c) A-gamma * d) A-delta * e) B

Answer 86

c) A-gamma (motor to muscle spindles) A-alpha is somatic motor and proprioception A-beta is touch and pressure A-delta is pain, cold, touch B is pre-ganglionic autonomic C is either post-ganglionic sympathetic, or pain, Temp, some mechano-receptors

Question 87

29 Regarding neuromuscular transmission, which statement is INCORRECT? * a) smooth muscle cells possess synapses en passant * b) about 10 times as much acetylcholine as is required is released at skeletal muscle neuromuscular junctions * c) antibodies can develop to calcium channels in nerve endings at neuromuscular junctions * d) more than one nerve fibre ends on each end-plate in skeletal muscle * e) acetylcholine is released by exocytosis

Answer 87

d) *One nerve fibre ends on one NMJ end-plate* Multiunit smooth muscle has synapses en passant Unitary smooth muscle acts as a syncytium with gap junctions

Question 88

30 Regarding the structure of skeletal muscle, which statement is INCORRECT? * a) thick filaments consist of myosin * b) actin forms a doublehelix * c) thin filaments include tropomyosin * d) troponin-I inhibits interaction between actin and myosin * e) T-system lies at Z-lines

Answer 88

e) T-system lies at Z-lines T-system is at Z-lines in cardiac muscle Junction A and I bands in skeletal muscle

Question 89

31 Which of the following nerve fibre types has the fastest conduction velocity? * a) B * b) A-delta * c) A-beta * d) A-gamma * e) C

Answer 89

c) A-beta

Question 90

32 Regarding the nerve fibre action potential, which statement is INCORRECT? * a) does not involve calcium ions * b) after-depolarisation commences when depolarisation is 70% complete * c) total number of ions involved is minute compared to the total number present * d) spike potential peaks at sodium equilibrium potential * e) firing level (threshold) is at about -55mV

Answer 90

d) spike potential peaks at sodium equilibrium potential Starts to reach it, but the electrical gradient switches, slowing outflow, and Na channels close quickly

Question 91

33 Which of the following nerve fibre types is MOST sensitive to local anaesthetic blockade? * a) A-alpha * b) A-gamma * c) A-delta * d) B * e) C

Answer 91

e) C C fibres are most sensitive to local anaesthetics Larger diameter fibres are most sensitive to pressure, so Aa \> Ab \> Ay \> Ad \> B \> C B cells are most sensitive to hypoxia

Question 92

34 Regarding neurotoxins, which statement is INCORRECT? * a) tetrodotoxin is a sodium channel blocker * b) tetraethylammonium is a potassium channel blocker * c) tetanospasmin interferes with GABA release * d) botulinum toxin blocks release of acetylcholine * e) latrotoxin causes explosive release of acetylcholine

Answer 92

All appear to be right. Tetanus toxin is uptaken by pre-synaptic membrane of NMJ → cell body and is then picked up by presynaptic membrane of inhibitory interneurons where it blocks release of GABA and glycine. This causes a decrease in inhibition, and thus a spastic paralysis (tetani) Botulinum inhibits proteins that are necessary for synaptic vesicles to fuse with the cell membrane, thus preventing ACh release and causing a flaccid paralysis Tetrodotoxin is a Na blocket TEA is a K+ blocker Latrotoxin inserts pores into the cell membrane causing rapid influx of oins including Ca, which leads to massive ACh release.

Question 93

35 Regarding conduction of nerve impulses, which statement is INCORRECT? * a) it is an active, self-propagating process * b) salutatory conduction occurs in unmyelinated neurons * c) axons can conduct impulses in either direction * d) conduction velocity is proportional to nerve fibre diameter * e) “current sink” occurs in neuronal cell membrane ahead of impulse

Answer 93

b) salutatory conduction occurs in *myelinated* neurons ## Footnote This is the process of the AP jumping from one node of ranvier to the next.

Question 94

36 B nerve fibres transmit impulses of which modality? * a) proprioception * b) preganglionic autonomic * c) temperature * d) postganglionic sympathetic * e) somaticmotor

Answer 94

* b) preganglionic autonomic A-alpha is somatic motor and proprioception A-beta is touch and pressure A-gamma is motor to muscle spindles A-delta is pain, cold, touch B is pre-ganglionic autonomic C is either post-ganglionic sympathetic, or pain, Temp, some mechano-receptors

Question 95

37 Regarding nerve fibres, which statement is INCORRECT? * a) resting membrane potential is about -90mV * b) action potentials are generated at the initial segment in spinal motor neurons * c) myelin produces up to 50 times faster conduction of impulses * d) membrane is more permeable to potassium than sodium at rest * e) sodium channels are highly concentrated at the nodes of ranvier

Answer 95

a) resting membrane potential is about *-70mV* Cardiac and skeletal muscle has a RMP of -90mV

Question 96

38 Regarding skeletal muscle, which statement is INCORRECT? * a) resting membrane potential is about -90mV * b) resting length is the length at which active tension in the muscle is maximal * c) total glycogen stored is about 0.4kg * d) energy source at rest is mainly glucose * e) resting heat production is due to basal metabolic processes

Answer 96

d) energy source at rest is mainly lipids, mostly FFAs At exercise carbohydrate is primarily used. This can be glucose from the blood stream, or glycogen. These are broken down into pyruvate. If adequate O2 is availble, they enter the citric acid cycle and generate ATP by being converted to CO2 + H20 (aerobic metabolism). If inadequate O2 is available, pyruvate is broken down into lactate and ATP (anaeorbic metabolism). Aerobic metabolism produces about 10x as much ATP per unit of glucose than anaerobic (40 ATP per glucose or glycogen vs 4 ATP)

Question 97

39 Which of the following nerve fibre types has the LEAST myelin? * a) A-alpha * b) A-beta * c) A-gamma * d) B * e) C

Answer 97

e) C (unmyelinated)

Question 98

40 A-alpha nerve fibres transmit impulses of which modality? * a) proprioception * b) pain * c) pressure * d) touch * e) motor to muscle spindles

Answer 98

a) proprioception A-alpha is somatic motor and proprioception A-beta is touch and pressure A-gamma is motor to muscle spindles A-delta is pain, cold, touch B is pre-ganglionic autonomic C is either post-ganglionic sympathetic, or pain, Temp, some mechano-receptors

Question 99

41 Unmyelinated neurons: * a) do not have Schwann cells associated with them * b) display salutatory conduction * c) constitute most of the cell population in the human central nervous system * d) do not occur in humans * e) none of the above are true

Answer 99

They think e) none of the above. Schwann cells make myelin in the PNS. Nonmyelinating Schwann cells are involved in maintenance of axons and are crucial for neuronal survival

Question 100

42 In skeletal muscle: * a) thick filaments which are made up of myosin and tropomyosin are lined up to form A bands * b) the dark A band has a light H band in its centre which in turn has an M line in its middle * c) thick filaments are made up of actin, tropomyosin and troponin and form the H band * d) Z lines are connected to the thick filaments * e) during contraction, the width of the A band reduces

Answer 100

b) the dark A band has a light H band in its centre which in turn has an M line in its middle * a) thick filaments which are made up of *just myosin* are lined up to form A bands * c) *thin* filaments are made up of actin, tropomyosin and troponin and form the I band (although there is no specific band correlating just to the thin filament) * d) Z lines are connected to the *thin* filaments * e) during contraction, the width of the A band *remains the same*

Question 101

43 Dorsal root (type C) fibres: * a) conduct proprioception * b) are amongst the largest of the nerve fibres * c) are the fibres most susceptible to hypoxia * d) administration of lignocaine suppresses transmission in C fibres before affecting A fibres * e) are myelinated

Answer 101

d) administration of lignocaine suppresses transmission in C fibres before affecting A fibres

Question 102

44 Saltatory conduction: * a) only occurs in myelinated neurons * b) is slower than non-saltatory conduction * c) is unaffected by local anaesthetics * d) does not occur with anti-dromic conduction * e) is directly proportional in rate to the size of the action potential

Answer 102

a) only occurs in myelinated neurons

Question 103

45 A motor unit is made up of: * a) a flexor muscle and an extensor muscle * b) a single skeletal muscle and all the motor neurons that supply it * c) a single motor neuron and all the muscle fibres it innervates * d) a large bundle of muscle fibres * e) all the motor neurons in which responses are observed after maximal stimulation of a single sensory nerve

Answer 103

c) a single motor neuron and all the muscle fibres it innervates

Question 104

46 The role of calcium in excitation/contraction couple in skeletal muscle is: * a) by binding troponin C it uncovers the binding site of actin to interact with the myosin head * b) by binding troponin I, it uncovers the binding site of actin to interact with the myosin head * c) by binding to tropomyosin, it allows troponic to bind to myosin * d) by binding to troponin C, it allows the myosin head to disengage resulting in relaxation * e) it causes depolarisation to spread along the tubules

Answer 104

a) by binding troponin C it uncovers the binding site of actin to interact with the myosin head

Question 105

47 A decrease in extracellular K+: * a) makes the resting membrane more negative in nerve cells * b) causes a similar effect in nerve cells as a decrease in extracellular Na+ * c) has little effect in nerve cell membrane potential * d) may decrease nerve cell action potential size * e) cause a similar effect in nerve cells as an increase in extracellular Ca++

Answer 105

e) cause a similar effect in nerve cells as an increase in extracellular Ca++

Question 106

48 Tetanic contraction of skeletal muscle: * a) occurs because of the short refractory period of skeletal muscle * b) is due to increased calcium available for binding to troponin C * c) enables a tension development of approximately four times that of individual twitch contraction * d) occurs only with isometric contractions * e) has the same mechanism of that of cardiac muscle

Answer 106

c) enables a tension development of approximately four times that of individual twitch contraction Occurs due to a high-frequency of motor neuron APs, and can happed with muscle lengthening, shortening, or isometric contractions Cardiac muscle cannot undergo tetanus

Question 107

49 With respect to nerve fibre types: * a) the speed on conduction is inversely proportional to the diameter of the fibre * b) C fibres are more susceptible to local anaesthetics than A fibres * c) Aδ fibres are concerned primarily with somatic motor function * d) pain may be relayed by all fibre types * e) Aδ fibres are efferent only

Answer 107

b) C fibres are more susceptible to local anaesthetics than A fibres

Question 108

50 In visceral smooth muscle * a) Ca2+ for contraction is released from sarcoplasmic reticulum * b) membrane potential has a resting value of -90mV * c) the excitation contraction coupling time is rapid (\<10ms) * d) muscle contracts when stretched in absence of innervation * e) binding of acetylcholine to nicotine receptors increases Ca2+ influx

Answer 108

d) muscle contracts when stretched in absence of innervation binding of acetylcholine to *muscarinic* receptors increases Ca2+ influx Unstable RMP Ca comes from multiple sources but SR is much smaller/less important than other muscles

Question 109

51 Inhibitory post synaptic potentials involve: * a) localised increase in membrane permeability to Na+ * b) localised decrease in membrane permeability to Cl- * c) localised increase in membrane permeability to PO4 * d) localised increase in membrane permeability to Cl- * e) localiseddecreaseinmembranepermeabilitytoK+

Answer 109

d) localised increase in membrane permeability to Cl-

Question 110

52 In skeletal muscle relaxation * a) there is a spread of depolarisation along T tubules * b) Ca2+ is released from troponin * c) there is increase Na+ and K+ conduction in the end plate membranes * d) a resting membrane potential of -65mV is finally reached * e) Mg2+ has a crucial role

Answer 110

b) Ca2+ is released from troponin

Question 111

53 Regarding synapses: * a) the synaptic cleft is 30-50mm wide * b) transmitters are released from synaptic knobs secondary to Na+ triggers * c) the amount of transmitter released is proportionate to Ca2+ efflux * d) acetylcholine is present in granulated vesicles in synaptic knob * e) the EPSP is caused by Na+ influx

Answer 111

e) the EPSP is caused by Na+ influx ACh is in small and clear vesicles Transmitters are released in response to Ca triggers Cleft is much smaller than 3-5cm (20-40nm)

Question 112

54 Which of the following is inhibitory neurotransmitter? * a) gallamine * b) acetylcholine * c) glutamate * d) glycine * e) aspartate

Answer 112

d) glycine

Question 113

55 Which of the following nerves is NOT of fibre type A? * a) proprioception * b) touch * c) motor to muscle spindles * d) somatic motor * e) dorsal root pain and temperature

Answer 113

e) dorsal root pain and temperature This is mediated by C fibres

Question 114

56 Which nerve fibre is MOST susceptible to local anaesthetics? * a) proprioception * b) touch * c) motor to muscle spindles * d) somaticmotor * e) dorsal root pain and temperature

Answer 114

e) dorsal root pain and temperature | (C fibres)

Question 115

57 Which nerves have the biggest diameter and faster conduction velocity? * a) groupAalpha * b) groupAbeta * c) group A gamma * d) groupAdelta * e) groupC

Answer 115

a) groupAalpha

Question 116

58 In excitation-contraction of skeletal muscle, calcium binds to: * a) tropomyosin * b) myosin * c) troponin I * d) troponinC * e) troponinT

Answer 116

d) troponinC

Question 117

59 Myosin binding sites on actin are normally covered by: * a) troponinI * b) troponinC * c) troponin T * d) tropomyosin * e) ryanodinemolecule

Answer 117

a) troponin I

Question 118

60 With regard to skeletal muscle, which is INCORRECT? * a) the terminal cisterns of sarcoplasmic reticulum lie in contact with T tubules * b) the T tubules surround the muscle at its Z lines * c) the Z line lies within the I band * d) the M line is due to a central bulge in each of the thick filaments * e) the area between two adjacent Z lines is called a sarcomere

Answer 118

b) the T tubules surround the muscle at its Z lines (between A and I band in skeletal muscle) At the z-line in *cardiac muscle*

Question 119

61 Noradrenaline: * a) is the main neurotransmitter of the parasympathetic nervous system * b) acts at sympathetic neuromuscular junctions in skeletal muscle and vascular smooth muscle * c) is secreted by the adrenal medulla * d) causes pupillary constriction * e) reduces blood pressure

Answer 119

c) is secreted by the adrenal medulla

Question 120

62 Acetylcholine: * a) is a major neurotransmitter in the spinal cord * b) is degraded within the neuromuscular end-plate by dehydration * c) is important in the stimulation of pancreatic function * d) is the neurotransmitter involved in vagal stimulation of the heart * e) is antagonised by neostigmine

Answer 120

c) is important in the stimulation of pancreatic function

Question 121

63 The action potential of a neuron: * a) is initiated by efflux of Na+ * b) is terminated by efflux of K+ * c) declines in amplitude as it moves along the axon * d) results in transient reversal of the concentration gradient of Na+ across the cell membrane * e) is not associated with any net movement of Na+ or K+ across the cell membrane

Answer 121

b) is terminated by efflux of K+

Question 122

64 The functions of tropomyosin in skeletal muscle include: * a) releasing Ca2+ after an action potential * b) sliding on actin to produce shortening * c) binding to myosin during contraction * d) acting as a “releasing protein” at rest by covering up the sites where myosin binds to actin * e) generating ATP which passes to the contractile mechanism

Answer 122

d) acting as a “releasing protein” at rest by covering up the sites where myosin binds to actin

Question 123

65 Membrane potential: * a) is only found in nervous tissue * b) is not contributed to by the Na+ /K+ pump * c) magnitude does not change from tissue to tissue * d) is negative inside in relation to the outside * e) is mainly caused by leaking Na+ / K+ channels

Answer 123

d) is negative inside in relation to the outside

Question 124

66 Gamma amino butyric acid: * a) is an excitatory mediator in the brain * b) is formed by decarboxylation of glutamate * c) acts at three different classes of GABA receptors * d) is mostly secreted unchanged in the urine * e) is the main mediator in glutamate

Answer 124

b) is formed by decarboxylation of glutamate

Question 125

67 Substance P: * a) is a carbohydrate * b) is a polypeptide found in the intestine and nervous tissue * c) is a β II amino acid residue mainly found in the liver * d) is not involved in the neuroendocrine system * e) is a lipid

Answer 125

b) is a polypeptide found in the intestine and nervous tissue

Question 126

68 Opioid peptides: * a) are not formed from precursors * b) include morphine as an example * c) form the opioid receptors in the brain * d) are mainly found in the brain and gastrointestinal tract * e) are almost always excreted unchanged

Answer 126

d) are mainly found in the brain and gastrointestinal tract

Question 127

69 Regarding the autonomic nervous system: * a) does not have a reflex arc like somatic nervous system * b) has dopamine as the main transmitter * c) has cholinergic division which increases activity of the intestinal musculature and increases gastric secretion * d) neurotransmitter noradrenaline is metabolised by pseudocholinesterase * e) is not involved with visceral sensation

Answer 127

c) has cholinergic division which increases activity of the intestinal musculature and increases gastric secretion * a) does have reflex arcs like somatic nervous system (eg pupillary constriction) * b) has *ACh + noradrenaline* as the main transmitter * d) neurotransmitter noradrenaline is metabolised by *COMT and MAO* * e) is not involved with visceral sensation

Question 128

70 Contraction of skeletal muscle is initiated by Ca++ binding to: * a) tropomyosin * b) myosin * c) actin * d) troponinC * e) troponinI

Answer 128

d) troponinC

Question 129

71 The stretch reflex in skeletal muscle: * a) is a feedback reflex aimed at maintaining muscle length * b) is a polysynaptic reflex * c) maintains muscle strength at various levels of muscle strength * d) is not elicited in the knee jerk which occurs after tapping * e) noneoftheabovearetrue

Answer 129

a) is a feedback reflex aimed at maintaining muscle length

Question 130

72 Excitary amino acids in the brain are: * a) glutamate and GABA * b) GABA and glycine * c) glutamate and glycine * d) glycine and aspartate * e) glutamate and aspartate

Answer 130

e) glutamate and aspartate

Question 131

73 The opioid δ receptor is involved in: * a) analgesia * b) respiratorydepression * c) miosis * d) dependence * e) all of the above

Answer 131

a) analgesia

Question 132

74 With regard to contraction and relaxation of skeletal muscle, all of the following are true EXCEPT: * a) contraction involves the release of K+ from the terminal cisterns * b) relaxation involves the release of Ca2+ from troponin * c) prior to contraction, increase Na+ and K+ conduction occurs in the end-plate membrane * d) relaxation involves cessation of the interaction between actin and myosin * e) contraction involves inward spread of depolarisation along T tubules

Answer 132

a) contraction involves the release of K+ from the terminal cisterns

Question 133

75 Regarding nerve fibres: * a) type C myelinated fibres in the dorsal root conduct impulses concerning pain and * temperature * b) type A α unmyelinated fibres conduct impulses concerning proprioception * c) type A β unmyelinated fibres conduct impulses concerning light touch * d) type A γ unmyelinated fibres conduct impulses to muscle spindles * e) type B myelinated fibres are located in preganglionic autonomic region

Answer 133

e) type B myelinated fibres are located in preganglionic autonomic region

Question 134

76 With regard to chemoreceptors, all of the following are true EXCEPT: * a) the medullary chemoreceptors respond to a change in blood pCO2 * b) the medullary chemoreceptors respond to blood (H+) * c) the predominant peripheral chemoreceptors are located in the carotid and aortic bodies * d) the peripheral chemoreceptors respond to pO2 * e) the peripheral chemoreceptors respond to blood (H+)

Answer 134

**b) the medullary chemoreceptors respond to blood (H+)** *Respond to CSF H+. CO2 can diffuse easily in from the blood (and be hydrated to HCO3 + H), whereas HCO3 and H+ do not readily cross the BBB.*

Question 135

77 In the autonomic nerve system, β antagonism results in: * a) constriction of the renal vasculature * b) decreased velocity of conduction in the atrioventricular node * c) decreased velocity of conduction in the HIS/Purkinje system * d) decreased ventricular contractility * e) increased insulin and glucagon secretion

Answer 135

Unsure if the question is right. B, C, D all seem right. They think e) increased insulin and glucagon secretion, but insulin is inhibited by alpha neurons (not beta) B *agonism* leads to increased AV + HIS/Purkinje conduction **and** ventricular contractility, so antagonism should reduce all this *a1 agonism* -\> renal arteriole vasoconstriction, beta-2 agonism -\> systemic vein dilation

Question 136

78 The reticular activating system: * a) has depressed conduction during anaesthesia * b) is located in the pons * c) is a simple collection of parallel nerve fibres * d) has no input from the cranial nerves * e) is electrically isolated from the cerebral cortex

Answer 136

a) has depressed conduction during anaesthesia