Biological Systems MCAT Practice Exam

According to place theory, what determines pitch in hearing?

1. The amplitude of sound waves.

2. The rate of action potentials.

3. The regions of the basilar membrane that vibrate.

4. The size of the cochlea.

The correct answer is: The regions of the basilar membrane that vibrate.

Place theory suggests that the perception of pitch is determined by the specific location along the basilar membrane of the cochlea that vibrates in response to different frequencies of sound. According to this theory, different frequencies cause different parts of the basilar membrane to displace maximally; for instance, high-frequency sounds stimulate areas closer to the base of the cochlea, while low-frequency sounds stimulate areas closer to the apex. This spatial arrangement allows the auditory system to effectively discriminate between different pitches based on where the maximum vibration occurs. The other options do not accurately describe how pitch is determined according to place theory. While amplitude can influence volume rather than pitch, the rate of action potentials is more aligned with frequency theory, which relates to how often neurons fire in response to sounds rather than the location of the sound's peak vibration. Finally, the size of the cochlea is not a determining factor in pitch perception as described by place theory; rather, the functional characteristics and frequency response of the basilar membrane itself are what matter most.