What occurs when outer hair cells of the spiral organ are stimulated by motor neurons from the pons?

• A. The outer hair cells release neurotransmitters to directly stimulate auditory nerve fibers.
• B. The outer hair cells secrete endolymph into the cochlear duct.
• C. The outer hair cells change length, amplifying the movement of the basilar membrane.
• D. The outer hair cells initiate action potentials that travel to the auditory cortex.

Answer: (C)

Verified step by step guidance

1. Understand the role of outer hair cells in the spiral organ (organ of Corti). Outer hair cells are specialized cells in the cochlea that primarily function to amplify sound vibrations rather than directly transmitting auditory signals.
2. Recognize that outer hair cells are stimulated by motor neurons originating from the pons. This stimulation causes the outer hair cells to change their length through a process called electromotility, which is driven by the motor protein prestin.
3. Electromotility of the outer hair cells enhances the movement of the basilar membrane. This amplification increases the sensitivity and frequency selectivity of the cochlea, allowing for more precise detection of sound waves.
4. Clarify that outer hair cells do not release neurotransmitters to directly stimulate auditory nerve fibers. Instead, inner hair cells are responsible for releasing neurotransmitters to activate auditory nerve fibers and initiate action potentials.
5. Note that outer hair cells do not secrete endolymph into the cochlear duct or directly initiate action potentials traveling to the auditory cortex. Their primary role is mechanical amplification of sound vibrations to assist inner hair cells in signal transduction.