Chapter 47, Problem 2TYK

In the human ear, how do different hair cells respond to different frequencies of sound?

a. Waves of pressure move through the fluid in the cochlea.

b. Hair cells are "sandwiched" between membranes.

c. Receptors in the stereocilia of each hair cell are different, each receptor protein responds to a certain range of frequencies.

d. Because the basilar membrane varies in stiffness, it vibrates m certain places in response to certain frequencies.

Summary Introduction

Introduction:

The human ear, is also involved in the maintenance of balance in the body, apart from performing the function of hearing. Cochlea is a part of inner ear that contains three different fluid filled chambers, lined by different membranes- Reissner’s membrane, tectorial membrane and basilar membrane. The hair cells are present on the basilar membrane, along with their projections known as stereocilia. These cells are covered by a thin tectorial membrane.

Answer to Problem 2TYK

Correct answer:

The difference in the stiffness of the basilar membrane at some places leads to its vibration at certain places in response to certain frequencies. A sound of particular frequency vibrates the particular region; thus, the hair cells of that area only will bend.

Explanation of Solution

Explanation/Justification for the correct answer:

Option (d) is given as the stiffness variation of the basilar membrane and the vibration of hair cells in response to certain frequencies. The basilar membrane varies in the stiffness, the narrow portion vibrates in response to high frequencies whereas the wide portion vibrates in response to low frequencies. The hair cells present in the particular region on the membrane respond to the sound of a particular frequency. Hence, option (d) is correct.

Explanation for incorrect answers:

Option (a) is given that the movement of the waves of pressure through fluid in the cochlea causes response of different hair cells in response to different sound frequencies. Waves of pressure that moves through endolymph and perilymph in cochlea does not produces specific vibration in different regions. So, it is a wrong answer.

Option (b) is given that the hair cells are sandwiched between the membranes. The hair cells are embedded in the tissue that sits atop the basilar membrane. In addition to this, the hair cells touch another small surface known as a tectorial membrane. However, it does not describe the response of the hair cells to different frequencies. So, it is a wrong answer.

Option (c) is given that each hair cells have different receptors in their stereocilia, and the generation of the response depends upon a certain range of frequencies. However, it is not the mechanism of response generation by the hair cells in order to aid hearing. So, it is a wrong answer.

Hence, options (a), (b), and (c) are incorrect.

Conclusion

Thus, it can be concluded that the hair cells, which are present in the basilar membrane, generate response to different frequencies as a result of variation in the stiffness of the basilar membrane. Furthermore, the vibration occurs only in response to certain frequencies.