Question

Increases in loudness are coded by:

A) the activation of more hair cells.
B) the activation of more bipolar cells.
C) an increased rate of firing in bipolar cells.
D) activation of loudness detectors in the medial geniculate nucleus.

Answer 1

Increases in loudness are encoded by the activation of more hair cells on the basilar membrane, with a greater number of hair cells stimulated corresponding to the perception of higher volume.

Step-by-step explanation:

Increases in loudness are coded by the activation of more hair cells. When the hair cells on the basilar membrane are stimulated by sound waves, they respond by bending and opening gated ion channels, leading to the depolarization of the cell membrane.

This results in a transmitted signal to the cochlear nerve. The intensity or volume of a sound is determined by how many hair cells are stimulated at a particular location. The more hair cells that are activated, the louder the sound is perceived. These hair cells are arranged in such a way that different regions of the basilar membrane and therefore, different hair cells, respond to different frequencies.

In this context, pitch perception and loudness are distinct; pitch is determined by the location along the cochlear duct that hair cells are stimulated, whereas loudness is determined by the number of hair cells stimulated.