Question

22. How are hair cells in the inner ear depolarized? (A) Mechanically-gated K channels open. (B) Voltage-gated Na channels open. (C) Voltage-gated Cap channels open. (D) Cat-activated Cl channels open. 23. Phase locking is used for sound frequencies up to around 1000 Hz. At higher frequencies, tonotopy is used. The note "concert pitch A", or 440 Hz, is commonly used to tune instruments in an orchestra or musical ensemble. If an instrument is playing concert pitch A, how fast are action potential spikes in the auditory nerve? (A) 440 Hz (B) 1100 Hz (C) 1000 - 440 = 60 Hz (D) This is a trick question. Action potentials are all-or-none and therefore do not change frequencies. 24. (Continued from Q23) Let's say that the maximum firing rate for the auditory nerves that receive input from the hair cells is 1000 Hz. The maximum frequency range for human hearing is around 20 kHz (20,000 Hz). If a 20 kHz sound is played, how fast are action potential spikes in the auditory nerve? (A) 1000 Hz (B) 20 kHz (C) 20kHz - 1000 Hz = 19 kHz (D) This is a trick question. Action potentials are all-or-none and therefore do not change frequencies. 25. Interaural time delay is used for binaural location of sound. If a sound is played to the left of your head, you would expect: (A) a temporal summation in the left superior olive. (B) a temporal summation in the right superior olive. (C) a spatial summation in the left superior olive. (D) a spatial summation in the right superior olive.

Answer 1

QUESTION 22

The correct answer is Mechanically-gated K channels open.
The stereocilia of the sensory cells are the place of the mechano-electrical transduction. In brief words, the vibration of the sound (mechanical stimulus) is converted into the nervous message that can be interpreted by the brain.

Depolarization of hair cells is linked to the opening of cationic channels, probably located in the upper part of the stereocilia. The apical bridges that exist between the stereocilia allow the simultaneous opening of these channels that allow potassium (K+) to pass through. The K + gradient is due to the composition of the endolymph, which is very rich in this element.