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

• A. Vestibule
• B. Base
• C. Scala media
• D. Apex

Answer: (B)

High-frequency sounds activate the base of the cochlea because the basilar membrane is stiff and narrow there, so it responds best to rapid cycles of vibration. The cochlea is organized so that different frequencies peak at different places along its length: high frequencies peak near the base, while low frequencies peak near the apex as the membrane becomes wider and more flexible. When a high-frequency sound enters the cochlea, the traveling wave reaches its maximum displacement near the base, stimulating the corresponding hair cells to transduce those vibrations into neural signals. The vestibule is part of the balance system and not involved in hearing, and the scala media is a fluid-filled duct within the cochlea—not the specific site of high-frequency activation.