Anatomy and Physiology of Hearing Flashcards

Which ossicle directly contacts the oval window of the cochlea?

Answer: Stapes

The stapes footplate fits into the oval window, transmitting vibrations from the ossicular chain directly into the perilymph of the inner ear.

The impedance matching function of the middle ear is primarily achieved by:

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.

The superior semicircular canal detects head movement in which plane?

Answer: Sagittal (pitch)

The superior (anterior) semicircular canal is oriented to detect pitch movements (nodding the head forward and backward).

What is the resting membrane potential of a healthy inner hair cell?

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.

Which structure produces endolymph in the inner ear?

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.

The acoustic reflex (stapedius reflex) serves primarily to:

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.

Hair cell stereocilia are connected at their tips by structures called:

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.