What type of ion channel is opened by sound-induced vibrations in hair cells of the cochlea?

• A. A. Chemically gated
• B. B. Mechanically gated
• C. C. Electrically gated
• D. D. Synaptically gated

Answer: (B)

The correct answer is that the type of ion channel opened by sound-induced vibrations in hair cells of the cochlea is mechanically gated. Hair cells in the cochlea are sensitive to mechanical stimuli, such as sound vibrations, which cause the stereocilia (small hair-like projections) on the hair cells to bend. This mechanical deformation opens ion channels in the cell membrane.

When the stereocilia are displaced by sound waves, mechanosensitive ion channels, which are inherently designed to respond to mechanical changes, open. This influx of ions, predominantly potassium and calcium, leads to depolarization and synaptic signaling that transmits auditory information from hair cells to the auditory nerve fibers. This process is fundamental to the conversion of sound waves into electrical signals that the brain can interpret as sound.

Other types of channels, such as chemically gated, electrically gated, or synaptically gated channels, involve different mechanisms (such as action potentials initiated by neurotransmitter binding or changes in electric potential) and are not responsible for the initial response to sound vibrations.