IHS Anatomy and Physiology of Hearing 3 — Questions and Answers
Question 1: Which ossicle directly contacts the oval window of the cochlea?
- Malleus
- Incus
- Stapes (Correct answer)
- Lenticular process
Correct answer: Stapes
The stapes footplate fits into the oval window, transmitting vibrations from the ossicular chain directly into the perilymph of the inner ear.
Question 2: The impedance matching function of the middle ear is primarily achieved by:
- The resonance of the ear canal
- The ratio of tympanic membrane area to stapes footplate area (Correct answer)
- The elasticity of the round window membrane
- The tension of the tensor tympani muscle
Correct answer: The ratio of tympanic membrane area to stapes footplate area
The large tympanic membrane area (approximately 55 mm²) compared to the small stapes footplate (approximately 3.2 mm²) creates a pressure gain that matches air impedance to fluid impedance.
Question 3: The superior semicircular canal detects head movement in which plane?
- Horizontal (yaw)
- Sagittal (pitch) (Correct answer)
- Coronal (roll)
- All planes simultaneously
Correct answer: Sagittal (pitch)
The superior (anterior) semicircular canal is oriented to detect pitch movements (nodding the head forward and backward).
Question 4: What is the resting membrane potential of a healthy inner hair cell?
- Approximately +80 mV
- Approximately -60 mV (Correct answer)
- Approximately 0 mV
- Approximately -130 mV
Correct answer: Approximately -60 mV
Inner hair cells maintain a resting membrane potential of approximately -60 mV, which becomes less negative (depolarizes) when stereocilia deflect toward the tallest bundle.
Question 5: Which structure produces endolymph in the inner ear?
- Reissner's membrane
- Stria vascularis (Correct answer)
- Spiral ligament
- Basilar membrane
Correct answer: Stria vascularis
The stria vascularis, a highly vascularized tissue lining the lateral wall of the scala media, actively secretes endolymph and maintains its high K⁺ concentration.
Question 6: The acoustic reflex (stapedius reflex) serves primarily to:
- Enhance high-frequency hearing
- Protect the cochlea from loud, low-frequency sounds (Correct answer)
- Equalize pressure in the middle ear
- Increase sensitivity to soft sounds
Correct answer: Protect the cochlea from loud, low-frequency sounds
Contraction of the stapedius muscle stiffens the ossicular chain, attenuating the transmission of intense low-frequency sounds and offering some cochlear protection.
Question 7: Hair cell stereocilia are connected at their tips by structures called:
- Gap junctions
- Tip links (Correct answer)
- Tight junctions
- Lateral links
Correct answer: Tip links
Tip links are fine filaments connecting the tip of each shorter stereocilium to the side of the adjacent taller one, gating mechanosensitive ion channels upon deflection.
IHS Anatomy and Physiology of Hearing 3
Which ossicle directly contacts the oval window of the cochlea?