What is the significance of the cochlear gradient?

• A. It allows for frequency-specific resonance along the basilar membrane
• B. It makes the ear respond equally to all frequencies
• C. It blocks low-frequency transmission
• D. It increases middle-ear impedance

Answer: (A)

The main idea tested is how the cochlea mechanically analyzes different frequencies along its length. The basilar membrane is graded in stiffness, width, and mass from base to apex, so each location has a preferred resonant frequency. When sound enters, a traveling wave forms on the basilar membrane and grows to a peak at a position determined by the frequency: high frequencies peak near the stiff, narrow base, while low frequencies peak toward the flexible, wide apex. This spatial distribution means different sets of hair cells are activated for different pitches, creating a tonotopic map that the auditory system reads as distinct frequencies. The gradient doesn’t make the ear respond equally to all frequencies, nor does it block low-frequency transmission or alter middle-ear impedance—the significance lies in creating frequency-specific resonance along the basilar membrane that underpins pitch discrimination.