Auditory Physiology

What causes firing of the lateral superior olivary nucleus to increase?

When the sound coming in from the ipsilateral ear is lound relative to the contralateral ear.

What is the ion (Na and K) content of Perilymph and Endolymph?

- Peri: high Na, low K - Endo: low Na, high K

The hair cells at the base of the Basilar membrane are (taller/shorter) and respond better to (higher/lower) frequencies.

- Shorter - Higher

Which nerves innervate the stapedius and the tensor tympani muscles?

- Stapedius: facial - Tensor: trigem

The hair cells at the apex of the Basilar membrane are (taller/shorter) and respond better to (higher/lower) frequencies.

- Taller - Lower

What are the main 3 crossing over points of the auditory pathway?

- Trapezoid body - Commisure between lateral lemnsci - Commisure between inferior colliculi

Of the type I and type II ganglion cells, which are more numerous? Which are more precisely tuned to frequency?

- Type I - Type I

Of the type I and type II ganglion cells, which synapse on 1-2 inner cells? Which synapse on >10 outer hair cells?

- Type I - Type II

Where do the scala vestibuli and scala tympani meet?

At the helicotrema

On which membrane is the Organ of Corti resting?

Basilar membrane

Which membrane separates scala tympani from scala media?

Basilar membrane

Where do medial olivocochlear efferent axons project to?

Bilaterally onto outer hair cells. - important in selectively tuning cochlea to important sounds.

Where is one location where auditory, visual and somesthetic information get integrated?

Deep layers of the superior colliculus.

Where do lateral olivocochlear efferent axons project to?

Ipsilateral inner hair cells.

Which membrane separates the scala vestibule from the scala media?

Reissner's membrane

Which compartment of the inner ear contains the Organ of Corti?

Scala media

True or False: Each hair cell is most responsive to a specific frequency.

TRUE WOW

What are the 3 main ways we determine loudness?

- Amplitue of Basilar membrane and hair cells increase. - High amplitude recruits hair cells from fringe regions of high amp region. - Outer hair cells become stimulated only when Basilar membrane reaches high intensity stimulus.

The Basilar membrane is more stiff at the (apex/base) and more flexible at the (apex/base).

- Base - Apex

What is the difference between Broca's and Wernicke's Aphasia?

- Broca: Speech is non-fluent - Wernicke: Comprehension is impaired.

What is the function of tip links?

- Connect the stereocilia - Pull channels open/closed with stereocilia movement.

When excitatory signals from both ears coincide in time, firing from the medial superior olivary nucleus (increases/decreases). As signals offset, firing (increases/decreases).

- Increase - Decrease - More firing when ipsi and contra signals are coming in at the same time.

How do the lateral and medial superior olivary nuclei aid in sound localization?

- Lateral: Compare intensity between ears. - Medial: Detects time lag between ears.

Where do low and high frequency sounds create the greatest amplitude of Basilar membrane movement?

- Low: apex - High: base