Hearing Science Quiz 10

Front 1

Auditory System

Back 1

very sensitive to sound pressure, and can distinguish small changes in frequency.

Transduction is non-linear.

Front 2

Cochlear Potentials

Back 2

cochlea contains endolymph and perilymph that create an 80 mv potential difference.

The hair cells and auditory nerve generate biochemical potentials based on sodium and potassium flow.

Front 3

Types of Electrical Potentials

Back 3

AC/DC

Alternating Current and Direct Current.

Front 4

Alternating Current

Back 4

potentials change as a function of tissue vibration within the cochlea.

Front 5

Direct Current

Back 5

baseline potential changes that do not vary once they occur.

Front 6

Potentials That Can Be Recorded From the Cochlea

Back 6

Resting Potentials
Summating Potentials
Cochlear Microphonics
Auditory Action Potentials

Front 7

Cochlear Microphonic

Back 7

AC potential difference appearing only during acoustic stimulus.

Reflects the intensity and frequency components of sound input.

Thought to originate at cilia bearing end of outer hair cells.

Front 8

Auditory Action Potential

Back 8

AC potential generated by the auditory nerve, rather than the cochlear structures.

Not a true cochlear potential.

Neurons near the base are stimulated before the apex.

Front 9

Auditory Action Potential Stimulation

Back 9

The differences in stimulation (base vs. apex) means that the neurons have timing differences.

Potentials can cancel each other out, or sum partially.

With a tone, the basal end is stimulated initially, with less synchronous firing from the apical portions.

Front 10

Auditory Action Potential Charge

Back 10

large potential is created by sum of synchronous discharges.

AP is usually negative, then positive, then later negative potential from central sources.

Reflects the neural output of the cochlea.

Front 11

Hair Cells

Back 11

Stimulate a neural response.

Remember that the basilar membrane and tectorial membrane move differently.

Front 12

Shearing

Back 12

different for inner and outer hair cells.

shearing is a particular type of bending where the tops of the stereocilia move more than the bottom.

Front 13

Shearing of Stereocilia

Back 13

mechanical energy is transduced into electrochemical energy.

the stereocilia need to be strong in order to resist breakage; otherwise they can get lost in the tectorial membrane.

Front 14

Outer Hair Cell Shearing

Back 14

stereocilia are attached to the tectorial membrane.

Front 15

Inner Hair Cell Shearing

Back 15

fluids trapped between stereocilia and tectorial membrane.

this fluid is theorized to help with the shearing action.

Front 16

Neural Transduction

Back 16

inner hair cells are neural transducers that start the neural process of hearing.

transduction in the inner hair cells takes place near the top of the hair cells (region of stereocilia).

Front 17

Tip Links

Back 17

act like a trap door by stretching and contracting; open like a gate and allow positive ion charge to enter hair cell.

Front 18

Outer Hair Cells

Back 18

acoustical pre-amplifiers.

feed energy back into the cochlea, and provide a cochlear amplifier for transducing small vibrations into neural impulses which can be "heard" by the brain.

Exhibit a type of active response; change in size due to acoustic stimulation. Prestin allows for a very fast motile response.

Front 19

Outer Hair Cell Motility

Back 19

changes in length and width, and the changes vary with the level of voltage.

changes affect the connection between the basilar membrane, and the tectorial membrane.

Changes in the biochemical vibratory pattern of the cochlea at the time of stimulation is due to the changes in the OHC length.

Changes allow for the high sensitivity of cochlear responses, ability to hear different sound frequencies, and non-linear cochlear function.

Front 20

depolarization

Back 20

length of the outer hair cell DECREASES with increasing voltage.

Front 21

hyperpolarization

Back 21

length of the outer hair cells INCREASES with decreasing voltage.

Front 22

Resting Potentials

Back 22

Direct current potentials that exist without acoustic stimulation.

there are three DC potentials that can be seen in the resting and responding cochlea.

The most significant is the EP; endocochlear or endolymphatic potential.

Front 23

Summating Potentials

Back 23

DC potentials occuring only when there is an acoustic stimulus.

Baseline shift when a stimulus is present.