Veterinary Physiology Quiz 33 Quiz InstructionsThis quiz consists of 20 multiple-choice questions.You will be awarded 5 marks for each correct answer. Question 1: Which of the following correctly describes the ionic composition of endolymph within the vestibular organ?High Na+ concentration and low K+ concentrationHigh K+ concentration and low Na+ concentrationEqual concentrations of Na+ and K+High Ca2+ concentration and low K+ concentration Question 2: Which sensory receptor structure is specifically responsible for detecting angular acceleration and deceleration during rotational head movements?Macula of the utricleMacula of the sacculeCrista ampullarisOrgan of Corti Question 3: Purkinje cell projections from the flocculonodular lobe of the cerebellum influence the vestibular nuclei through which of the following mechanisms and anatomical pathways?Excitatory influence via the rostral cerebellar peduncleInhibitory influence via the caudal cerebellar peduncleInhibitory influence via the middle longitudinal fasciculusExcitatory influence via the ventral funiculus Question 4: Lower motor neurons innervating which muscle group are facilitated by descending signals traveling in the vestibulospinal tract within the ventral funiculus?Flexor muscles of the limbsSmooth muscles of the visceraExtensor muscles of the trunk and limbsExtraocular muscles exclusively Question 5: An animal suffering from a unilateral lesion of the right vestibular nerve is clinically expected to exhibit head tilt, circling, and falling toward which side?To the left sideTo the right sideAlternating between right and left sidesBackward only Question 6: The medial longitudinal fasciculus (MLF) carries vestibular signals to the motor nuclei of which set of cranial nerves to coordinate reflexive extraocular eye movements?Cranial nerves II, III, and IVCranial nerves III, IV, and VICranial nerves IV, V, and VICranial nerves III, V, and VII Question 7: How are the sensory hair cells oriented relative to the striola in the macula of the utricle compared to that of the saccule?Utricular kinocilia face away from the striola, whereas saccular kinocilia face toward the striola.Utricular kinocilia face toward the striola, whereas saccular kinocilia face away from the striola.Both utricular and saccular kinocilia face uniformly toward the striola.Both utricular and saccular kinocilia face uniformly away from the striola. Question 8: The statoconial membrane covering the maculae contains dense crystals of calcium carbonate (statoconia). How dense are these crystals relative to the surrounding endolymph?Approximately equal in density to endolymphAbout twice as dense as endolymphAbout three times as dense as endolymphAbout ten times as dense as endolymph Question 9: The basic rhythmic patterns of limb movement during locomotion are generated by central pattern generators located primarily in which region of the central nervous system?Cerebral motor cortexBasal nucleiCerebellumThoracolumbar spinal cord Question 10: Match the anatomical/functional structures of the inner ear (Column I) with their corresponding physiological characteristics (Column II):Column I:1. Crista ampullaris2. Macula of utricle3. Endolymph4. PerilymphColumn II:i. High K+ concentration, low Na+ concentrationii. Contains otoconia / calcium carbonate crystalsiii. Enclosed by a gelatinous cupula devoid of statoconiaiv. Resembles CSF with high Na+ concentrationWhich of the following represents the correct matching?1-iii, 2-ii, 3-i, 4-iv1-ii, 2-iii, 3-iv, 4-i1-iii, 2-i, 3-ii, 4-iv1-iv, 2-ii, 3-i, 4-iii Question 11: Match the semicircular duct (Column I) with the specific directional polarization of its sensory hair cells (Column II):Column I:1. Lateral semicircular duct2. Anterior semicircular duct3. Posterior semicircular ductColumn II:i. Kinocilia positioned on the side facing away from the utricleii. Kinocilia positioned on the side facing toward the utricleWhich of the following represents the correct matching?1-ii, 2-i, 3-i1-i, 2-ii, 3-ii1-ii, 2-ii, 3-i1-i, 2-i, 3-ii Question 12: Match the ionic movement or channel event (Column I) with its direct outcome on sensory hair cell potential (Column II):Column I:1. Deflection of stereocilia toward the kinocilium2. Opening of voltage-gated Ca2+ channels at the cell base3. Outflow of K+ through basolateral Ca2+-activated channels4. Deflection of stereocilia away from the kinociliumColumn II:i. Hyperpolarization and decreased neurotransmitter releaseii. Opening of tip-link mechanically gated K+ channels causing apical K+ influx and depolarizationiii. Triggers neurotransmitter vesicle fusion and release into synaptic cleftiv. Restores basolateral hyperpolarization to close Ca2+ channels during active cycleWhich matching option is correct?1-ii, 2-iii, 3-iv, 4-i1-i, 2-iv, 3-iii, 4-ii1-iii, 2-ii, 3-i, 4-iv1-ii, 2-i, 3-iv, 4-iii Question 13: Consider the following statements regarding vestibular physiology:I. The direction of nystagmus is clinically defined by the direction of its quick phase.II. Vestibular nerve fibers have zero spontaneous firing rate when the head is completely stationary.III. Excitatory burst neurons initiating the quick phase of nystagmus are located in the parabducent nucleus of the reticular formation.IV. Linear acceleration maximally stimulates the crista ampullaris rather than the macula.Which of the above statements are correct?I and III onlyII and IV onlyI, II, and III onlyIII and IV only Question 14: Evaluate the following statements regarding motor regulation of locomotion:I. Interruption of descending motor tracts prevents a cat from walking rhythmically on a supported treadmill.II. Lower motor neuron lesions result in muscle atrophy.III. Tapping a tendon stretches intrafusal fibers and leads to an increased firing rate in Ia primary sensory fibers.IV. Gamma motor neurons are larger in diameter than alpha motor neurons and innervate extrafusal muscle fibers.Which combination of statements is correct?I and IV onlyII and III onlyI, II, and III onlyII, III, and IV only Question 15: Which of the following statements concerning vestibular pathways are TRUE?I. The vestibulospinal tracts descend in the ventral funiculus of the spinal cord.II. Unilateral damage to the caudal cerebellar peduncle leads to loss of cerebellar inhibition on ipsilateral vestibular nuclei.III. The slow phase of nystagmus moves the eyes in the same direction as head rotation to establish a new visual field.IV. In cats, vestibular projections reach the cerebral cortex via the vestibulo-thalamo-cortical pathway.I, II, and IV onlyI and III onlyII, III, and IV onlyI, II, III, and IV Question 16: Given below are two statements: an Assertion (A) and a Reason (R).Assertion (A): Deflection of stereocilia toward the kinocilium causes K+ ions to flow into the sensory hair cell from the surrounding endolymph.Reason (R): The endolymph bathing the apical surface of sensory hair cells possesses an unusually high potassium ion concentration.Which of the following is correct?Both (A) and (R) are true, and (R) is the correct explanation of (A).Both (A) and (R) are true, but (R) is NOT the correct explanation of (A).(A) is true, but (R) is false.(A) is false, but (R) is true. Question 17: Given below are two statements: an Assertion (A) and a Reason (R).Assertion (A): A unilateral lesion of the caudal cerebellar peduncle causes hyper-reactivity or disinhibition of the vestibular nuclei on the side of the lesion.Reason (R): Purkinje cells of the flocculonodular lobe exert an inhibitory efferent influence on the vestibular nuclei via the caudal cerebellar peduncle.Which of the following is correct?Both (A) and (R) are true, and (R) is the correct explanation of (A).Both (A) and (R) are true, but (R) is NOT the correct explanation of (A).(A) is true, but (R) is false.(A) is false, but (R) is true. Question 18: Arrange the following physiological events of sensory hair cell activation in their correct sequential order during head rotation:I. Opening of mechanically gated K+ channels at stereocilia apical tipsII. Influx of Ca2+ through basolateral voltage-gated channelsIII. Mechanical deflection of stereocilia toward the kinocilium stretching tip linksIV. Depolarization of the hair cell membraneV. Exocytosis of neurotransmitters into the synaptic cleft, increasing firing rate of the vestibular nerveWhich sequence correctly represents this process?III -> I -> IV -> II -> VI -> III -> II -> IV -> VIII -> IV -> I -> II -> VI -> IV -> III -> V -> II Question 19: During a rapid counterclockwise horizontal rotation of the head, what happens to the sensory hair cells and nerve firing rates in the left versus right lateral semicircular ducts?Stereocilia in the left ampulla bend toward kinocilia (increasing firing rate), while stereocilia in the right ampulla bend away from kinocilia (decreasing firing rate).Stereocilia in the right ampulla bend toward kinocilia (increasing firing rate), while stereocilia in the left ampulla bend away from kinocilia (decreasing firing rate).Hair cells in both left and right lateral ducts are equally depolarized.Hair cells in both left and right lateral ducts are hyperpolarized due to fluid pressure on the cupula. Question 20: When an animal's head is completely stationary and motionless, what is the activity level of the primary vestibular nerve fibers?Completely silent with zero action potentialsFiring spontaneously at a baseline rate of about 90 spikes per secondIrregularly bursting only when eye movements occurInhibited continuously by cerebellar Purkinje cells to zero spikes per second
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