Chapter 11 review questions Flashcards
How is the conduction of sound to the cochlea facilitated by the ossicles of the middle ear?
The tympanic membrane is moved by the sound waves, and the ossicles by the tympanic membrane. The signal is amplified by the ossicles.
Why is the round window crucial for the function of the cochlea? What would happen to hearing if it suddenly didn’t exist?
It has a flexible membrane that bulges out when the stapes moves the perilymph. Without it, hearing wouldn’t work as well as the perilymph would not be able to move in the same way.
Why is it impossible to predict the frequency of a sound simply by looking at which portion of the basilar membrane is most deformed?
It does not contain neurons with very low characteristic frequencies, so the site of maximal activation could be the same for 50 Hz and 200 Hz tones.
Why would the transduction process in hair cells fail if the stereocilia as well as the hair cell bodies were surrounded by perilymph?
The perilymph has a low K+ concentration and the K+ gates would no longer transmit current and depolarize the hair cell.
If inner hair cells are primarily responsible for hearing, what is the function of outer hair cells?
They amplify the sounds received by the inner hair cells.
Why doesn’t unilateral damage to the inferior colliculus or MGN lead to deafness in one ear?
Because only the cochlear nucleus receives input from just one ear; all other auditory nuclei, including inferior colliculus and MGN, receive input from both ears.
What mechanisms function to localize sounds in the horizontal and vertical planes?
Horizontal: Interaural time delay, interaural interaural intensity difference.
Vertical: Reflections from the pinna.
What symptoms would you expect to see in a person who had recently had a stroke affecting A1 unilaterally? How does the severity of these symptoms compare with the effects of a unilateral stroke involving V1?
The patient would not be able to localize the sound nearly as well as normally. With V1, the patient would be blind in one hemifield.
What is the difference between nerve deafness and conduction deafness?
Nerve deafness: Loss of either neurons in the auditory nerve or hair cells in the cochlea.
Conduction deafness: Disturbance in the conduction of sound from the outer ear to the cochlea.
Each macula contains hair cells with kinocilia arranged in all directions. What is the advantage of this arrangement compared to an arrangement of all the cells in the same direction?
The hair cell is very direction-sensitive: with kinocilia pointing in all directions, the vestibular system can read all kinds of head movement since only part of the hair cells is activated.
With all kinocilia pointing in the same direction, all movement might excite the hair cells in the same way.
Imagine a semicircular canal rotating in two different ways: around its axis (like a rolling coin) or end over end (like a flipped coin). How well would its hair cells respond in each case, and why?
Around the axis: The cupula bends and does excite the vestibular axons.
End over end: The cupula is not moved, and it does not excite the axons.
How would you expect the functions of the otolith organs and the semicircular canals to change in the weightless environment of space?
Otolith organs: Gravity no longer pulls the otoconia so head tilting would not be sensed normally.
Semicircular canals: Continue to work, but lack of gravity may influence their accuracy.
