Question

What specific event triggers activation of the stereocilia before they activate the auditory neuron?

A. The tectorial membrane vibrates and stretch-activated ion channels open on the stereocilia, polarizing the membrane.
B. Stretch-activated ion channels on the tectorial membrane open, both depolarizing and activating the stereocilia.
C. The stereocilia tilt when pushed against the tectorial membrane and stretch-activated ion channels open, releasing positive ions into the hair cell.
D. The basilar membrane vibrates and stretch-activated ion channels on stereocilia close, depolarizing the membrane.

Answer 1

The activation of stereocilia is triggered by their bending, due to pressure waves from sound causing the basilar membrane to move and the tectorial membrane to slide. This opens ion channels, depolarizing the hair cell membrane and sending signals down the cochlear nerve.

Step-by-step explanation:

The specific event that triggers activation of the stereocilia before they activate the auditory neuron occurs when pressure waves from sound move the basilar membrane in the cochlea. This movement causes the tectorial membrane to slide across the stereocilia, bending them. The bending of the stereocilia towards the tallest member of their array causes tension in protein tethers to open ion channels within the hair cells. This results in the depolarization of the hair cell membrane, subsequently sending nerve signals down the cochlear nerve.

When no sound is present, the stereocilia are upright with slight tension, keeping a small amount of depolarization at the membrane. The intensity of sound, or volume, is based on the quantity of hair cells that are stimulated at a specific location within the cochlea. Thus, the correct answer to what triggers the activation of stereocilia would be: C. The stereocilia tilt when pushed against the tectorial membrane and stretch-activated ion channels open, releasing positive ions into the hair cell.