Biology Forums - Study Force

1. Explain the results that might be obtained by performing the Rinne's and Weber's test on a patient with otosclerosis. How might these results compare with those obtained from a patient with sensory deafness?

2. How might the bending of hair cell processes lead to depolarization? Propose a general description of the function of hair cells in the animal kingdom.

3. Explain how different pitches of sound affect the basilar membrane and how this relates to the information sent to the brain.

1. A patient with otosclerosis has had “sclerotic bone” grow over their oval window and immobilize the foot plate of their stapes. These changes would impede the transmission of sound waves from the air to the cochlea of the inner ear. In Rine’s Test this patient would hear the vibrations being conducted through the mastoid process, because it is being conducted through bone and does not have to pass through the oval window. On the other hand, the patient would not hear the vibrations traveling through the air and into their external auditory meatus, because the bone growth has hindered the transmission of air to the cochlea. If you were to perform Weber’s Test on this patient the sound would seem louder in the affected ear, due to bone conduction.

In sensory deafness a patient will not be able to hear transmission of nerve impulses anywhere from the cochlea to the auditory cortex; this impairs the ability to hear some pitches more than others. Because there is no damage to the middle ear the patient would be able to hear the vibrations through the external auditory meatus. However, they would not hear the vibrations through the mastoid process because conduction would have to go through the inner ear. If you were to perform Weber’s Test on the patient the sound would seem louder in the normal ear.

2. When the hair cells are bent in the direction of the kinocilium, the cell membrane is pushed down and becomes depolarized. The hair cells then emit a synaptic transmitter which stimulates the dendrites of sensory neurons. When the hair cells are bent in the opposite direction, the membrane of the cell becomes hyperpolarized and release less synaptic transmitter.

3. Sounds of different pitches cause different parts of the basilar membrane to vibrate, exciting different sensory neurons in the cochlea. The sensory neurons then send their input to different regions of the auditory cortex.

Bio_man 8)