Hearing - Chapter 31

Question 1

Endolymph has a high concentration of which ion?

Answer 1

Potassium

Question 2

What structures are responsible for depolarizing hair cells in the ear?

Answer 2

Stereocilia and kinocilium

Question 3

What are the mechanisms that lead to the natural frequency oscillations in hair cells?

Answer 3

• The mechanical properties of each hair cell acts like a tuning fork in response to a pressure/rarefaction wave.
• The apex of the hair cell is bathed in potassium rich endolymph. When the hair is deflected and channels mechanically open K+ rushes into the cell having a depolarizing effect. This opens Voltage sensitive Ca2+ and K+ channels. The area around the base of the hair cell is K+ poor so K+ rushes out of the bottom to repolaraize the cell. In addition, the presence of Ca2+ opens Ca2+-gated K+ channels. This unique K+ gradient and combination of channels creates a natural frequency of voltage oscillations.