The region of the cochlea activated by low-frequency sounds is the?

• A. Apex
• B. Base
• C. Round window
• D. Middle

Answer: (A)

In the cochlea, different places along the basilar membrane respond to different frequencies—a pattern called tonotopy. The base of the cochlea is stiff and narrow, so it resonates best with high-frequency sounds. The apex is wider and more flexible, which allows it to be driven by longer wavelengths corresponding to low frequencies. When a low-frequency sound travels into the cochlea, the traveling wave travels farther along the membrane and peaks near the apex, where the hair cells transduce that mechanical movement into neural signals. The round window is simply a pressure release and isn’t a region of activation, and the base is tuned to high frequencies, not low. So the region activated by low-frequency sounds is the apex of the cochlea.