Which statement best describes outer hair cells?

Which statement best describes outer hair cells?

• A. They secrete perilymph into the middle ear.
• B. They are the primary sensory receptors.
• C. Inner hair cells amplify motion.
• D. Outer hair cells amplify motion.

Answer: (D)

Outer hair cells provide active amplification in the cochlea. They contract and elongate in response to vibration due to the motor protein prestin, injecting energy back into the basilar membrane. This electromotility boosts tissue motion for small sounds, increasing sensitivity and sharpening frequency tuning—the essence of the cochlear amplifier. They are not the primary sensory receptors (that role belongs to inner hair cells, which transduce vibration into neural signals). They do not secrete perilymph; perilymph is the fluid in the cochlear scalae and isn’t produced by hair cells. So the statement that outer hair cells amplify motion best captures their function.

Outer hair cells provide active amplification in the cochlea. They contract and elongate in response to vibration due to the motor protein prestin, injecting energy back into the basilar membrane. This electromotility boosts tissue motion for small sounds, increasing sensitivity and sharpening frequency tuning—the essence of the cochlear amplifier. They are not the primary sensory receptors (that role belongs to inner hair cells, which transduce vibration into neural signals). They do not secrete perilymph; perilymph is the fluid in the cochlear scalae and isn’t produced by hair cells. So the statement that outer hair cells amplify motion best captures their function.