What does the basilar membrane in the cochlea do?

What does the basilar membrane in the cochlea do?

• A. It varies in width and stiffness, responding to different frequencies of sound.
• B. It amplifies sound pressure.
• C. It transduces energy into neural signals.
• D. It filters sounds by amplitude.

Answer: (A)

The basilar membrane acts as a mechanical frequency analyzer. Its width and stiffness vary along its length: it is narrow and stiff at the base and wider and more flexible at the apex. This gradient makes different parts of the membrane resonate to different frequencies, so high-frequency sounds peak near the base and low-frequency sounds peak toward the apex. The resulting traveling wave sets up maximal displacement at specific locations, which is how the cochlea encodes frequency. Hair cells at those locations then transduce the mechanical movement into neural signals. The membrane itself doesn’t amplify sound pressure, and transduction is done by hair cells, not the basilar membrane, so the key feature is its frequency-selective mechanical response determined by the width and stiffness gradient.

The basilar membrane acts as a mechanical frequency analyzer. Its width and stiffness vary along its length: it is narrow and stiff at the base and wider and more flexible at the apex. This gradient makes different parts of the membrane resonate to different frequencies, so high-frequency sounds peak near the base and low-frequency sounds peak toward the apex. The resulting traveling wave sets up maximal displacement at specific locations, which is how the cochlea encodes frequency. Hair cells at those locations then transduce the mechanical movement into neural signals. The membrane itself doesn’t amplify sound pressure, and transduction is done by hair cells, not the basilar membrane, so the key feature is its frequency-selective mechanical response determined by the width and stiffness gradient.