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Physio: 9# Equilibrium
Q21. The vestibular apparatus is located in which part of the temporal bone?
Squamous
Tympanic
Petrous
Mastoid
Explanation:
Vestibular labyrinth lies in the petrous temporal bone.
Q22. Which structure senses linear horizontal acceleration?
Saccule
Posterior semicircular canal
Anterior semicircular canal
Utricle
Explanation:
Utricle detects horizontal linear movement and upright position.
Q23. Calcium carbonate crystals in the macula are called:
Otoliths
Cupula
Cristae
Endolymph
Explanation:
Otoliths increase inertia during linear acceleration.
Q24. Bending of stereocilia away from the kinocilium causes:
Excitation
Inhibition
No response
Action potential in hair cell
Explanation:
Away from kinocilium closes K⁺ channels → inhibition.
Q25. Angular acceleration is detected by:
Utricle
Saccule
Semicircular canals
Macula
Explanation:
Semicircular canals detect rotational movements.
Q26. During constant speed rotation, firing rate of vestibular nerve fibers:
Remains high
Progressively increases
Becomes zero
Returns to basal level
Explanation:
Endolymph catches up → cupula returns to neutral.
Q27. Sudden stopping after prolonged rotation causes:
Inhibition of previously excited canal
No vestibular response
Excitation of both canals
Loss of vestibular reflexes
Explanation:
Endolymph continues moving, bending cupula opposite.
Q28. Cold water irrigation of right ear causes nystagmus toward:
Right
Upward
Left
Downward
Explanation:
COWS: Cold → Opposite, Warm → Same.
Q29. Direction of nystagmus is determined by:
Slow phase
Vestibular phase
Endolymph movement
Fast corrective phase
Explanation:
Nystagmus direction is named by fast phase.
Q30. Vertigo is best described as:
Loss of balance
False sensation of rotation
Visual disturbance
Muscle weakness
Explanation:
Vertigo is illusion of movement without actual motion.
Q31. Vestibulo-ocular reflex helps to:
Initiate eye movements
Stop eye movements
Stabilize retinal image
Generate nystagmus
Explanation:
VOR keeps visual target fixed during head movement.
Q32. Head rotation to the right causes eyes to move:
To the left
To the right
Upward
Downward
Explanation:
VOR produces opposite eye movement.
Q33. Which cranial nerve nucleus is stimulated during rightward head rotation?
Left CN III
Right CN VI
Right CN IV
Right CN III
Explanation:
Right CN III activates right medial rectus.
Q34. Semicircular canals are arranged to detect movement in:
Two planes
Three orthogonal planes
Horizontal plane only
Sagittal plane only
Explanation:
Orthogonal orientation allows 3D rotation detection.
Q35. Each semicircular canal opens into the:
Saccule
Cochlea
Utricle
Endolymphatic sac
Explanation:
Semicircular canals open into utricle.
Q36. The sensory organ in the ampulla is the:
Crista ampullaris
Macula
Cupula
Otolith
Explanation:
Crista ampullaris contains hair cells.
Q37. The vestibular nerve projects directly to all EXCEPT:
Cranial nerve nuclei III, IV, VI
Spinal cord
Cerebellum
Auditory cortex
Explanation:
Vestibular input does not project directly to auditory cortex.
Q38. Physiologic nystagmus occurs during:
Sudden head stop
Prolonged rotation
Standing still
Sleep
Explanation:
Occurs when eyes reach extreme position during rotation.
Q39. The slow phase of physiologic nystagmus is:
Toward direction of rotation
Random
Opposite to direction of rotation
Vertical
Explanation:
Slow phase reflects vestibular reflex.
Q40. One major function of vestibular system is to control:
Extra-ocular muscles
Facial expression
Speech muscles
Respiration
Explanation:
Vestibular system coordinates eye movements and posture.