What occurs after hair-cell depolarization?

What occurs after hair-cell depolarization?

• A. Neurotransmitter release onto auditory nerve fibers
• B. Hyperpolarization of hair cells
• C. Immediate action potentials within hair cells
• D. Synthesis of myelin around the auditory nerve

Answer: (A)

Depolarization of cochlear hair cells opens voltage-gated calcium channels at the base of the cell, causing calcium influx that triggers exocytosis of glutamate-filled vesicles. The released neurotransmitter then activates receptors on the adjacent auditory nerve fibers (spiral ganglion neurons), exciting them to fire action potentials that travel along the auditory nerve to the brain. Hair cells themselves do not generate action potentials in the cochlea; their signal is a graded receptor potential that modulates transmitter release. Hyperpolarization would come after repolarization or inhibition, not as the immediate result of depolarization, and myelin around the auditory nerve is produced by glial cells along the nerve, not by hair cells.

Depolarization of cochlear hair cells opens voltage-gated calcium channels at the base of the cell, causing calcium influx that triggers exocytosis of glutamate-filled vesicles. The released neurotransmitter then activates receptors on the adjacent auditory nerve fibers (spiral ganglion neurons), exciting them to fire action potentials that travel along the auditory nerve to the brain. Hair cells themselves do not generate action potentials in the cochlea; their signal is a graded receptor potential that modulates transmitter release. Hyperpolarization would come after repolarization or inhibition, not as the immediate result of depolarization, and myelin around the auditory nerve is produced by glial cells along the nerve, not by hair cells.