IHS Anatomy and Physiology of Hearing 5 — Questions and Answers
Question 1: The tensor tympani muscle is innervated by which cranial nerve?
- Facial nerve (CN VII)
- Glossopharyngeal nerve (CN IX)
- Trigeminal nerve (CN V) (Correct answer)
- Vestibulocochlear nerve (CN VIII)
Correct answer: Trigeminal nerve (CN V)
The tensor tympani is innervated by the medial pterygoid nerve, a branch of the mandibular division (V3) of the trigeminal nerve (CN V).
Question 2: Which structure separates the scala media from the scala vestibuli?
- Basilar membrane
- Reissner's membrane (Correct answer)
- Tectorial membrane
- Spiral ligament
Correct answer: Reissner's membrane
Reissner's membrane (vestibular membrane) forms the thin boundary between the endolymph-filled scala media and the perilymph-filled scala vestibuli.
Question 3: Presbycusis caused by degeneration of the stria vascularis is classified as which type?
- Sensory presbycusis
- Neural presbycusis
- Strial (metabolic) presbycusis (Correct answer)
- Mechanical presbycusis
Correct answer: Strial (metabolic) presbycusis
Strial or metabolic presbycusis results from atrophy of the stria vascularis, reducing the endocochlear potential and causing a relatively flat audiometric configuration.
Question 4: The utricle detects which type of head movement or position?
- Rotational acceleration in the vertical plane
- Linear acceleration and static tilt in the horizontal plane (Correct answer)
- Angular velocity in the sagittal plane
- Vertical linear acceleration only
Correct answer: Linear acceleration and static tilt in the horizontal plane
The utricle's macula is oriented horizontally and responds to horizontal linear acceleration (such as moving forward) and head tilts relative to gravity.
Question 5: The number of inner hair cells in the human cochlea is approximately:
- 3,500 (Correct answer)
- 12,000
- 25,000
- 1,000
Correct answer: 3,500
There are approximately 3,500 inner hair cells arranged in a single row along the length of the cochlea, and they are the primary sensory cells sending signals to the auditory nerve.
Question 6: In the context of cochlear mechanics, 'phase locking' refers to:
- Hair cells firing only at the peak of the traveling wave location
- Auditory nerve fibers firing in synchrony with the phase of a stimulus frequency (Correct answer)
- The locking of the stapes footplate in otosclerosis
- Outer hair cells contracting at the same time as inner hair cells depolarize
Correct answer: Auditory nerve fibers firing in synchrony with the phase of a stimulus frequency
Phase locking means auditory nerve fibers fire at a preferred phase of each stimulus cycle, preserving temporal fine structure information especially for frequencies below ~4–5 kHz.
Question 7: Otoconia (otoliths) in the vestibular system are composed primarily of:
- Hydroxyapatite crystals
- Calcium carbonate (calcite) crystals (Correct answer)
- Sodium chloride crystals
- Calcium phosphate crystals
Correct answer: Calcium carbonate (calcite) crystals
Otoconia are tiny calcium carbonate crystals that rest on the gelatinous otolithic membrane of the utricle and saccule, adding inertia for detecting linear acceleration.
IHS Anatomy and Physiology of Hearing 5
The tensor tympani muscle is innervated by which cranial nerve?