Physio: Hearing Flashcards
What is impedence matching?
The ability of the auditory ossicles to convert sound waves in air into fluid waves in the perilymph.
What is the attenuation reflex in regards to hearing?
Contraction of the stapedius muscle during high intensity sounds in order to dampen the signal and thereby preventing injury to the auditory system.
Layer in the cochlea that lines the organ of corti and separates the endolymph from the perilymph.
Reticular Lamina
Structure that connects adjacent steriocilia to each other on hair cells.
Tip Links
Endolymph has a high postassium contain and contains a charge. What is the charge?
+80mV
What is the endocochlear potential?
The endolymph in the cochlear duct (scala media) has a resting potential of +80mV and the perilymph is neutral. The difference between these two electric potentials is the endocochlear potential.
What is the resting potential of a hair cell?
-70mV
(this creates a potential of 150mV allowing potassium to rush into and depolarize a cell once the stereocilia open the channels)
Describe the steps in hair cell depolarization and signal transmission to the auditory nerve.
- Sound wave/fluid wave displaces the basilar membrane.
- Hair cells are mobilized and the mechanosensitive K+ channels are opened depolarizing the hair cell.
- The hair cell depolarization opens voltage-gated Ca2+ channels.
- Increase in intracellular calcium causes NT vesicles containing glutamate to fuse and be released into the synapse.
- Opening of Ca2+ dependent K+ channels causes repolarization of the hair cell.
What is the function of Otoacoustic Emissions?
Tests the integrity of the inner ear.
sounds are sent into the ear and a recording device measures the waves sent back out thru the ROUND window
What is the best frequency?
Different for individual hair cells. It is the frequency of a sound that can be heard with the lowest intensity compared to sounds with other frequencies.
How is sound localization accomplished for low frequency sounds (20-2.2 Hz)?
Interaural Timing Disparities.
Low frequency sounds waves have a long wavelength and do not experience interference by the head. The brain analyzes the time difference from one ear detecting a sound vs. the second ear detecting a sound.
How is sound localization accomplished for high frequency sounds?
Interaural Intensity Disparities.
The high frequency sound waves have short wavelengths and the head interferes with the sound waves creating a difference in intensity between the two ears. The brain analyzes the difference and can locate the source of the sound.
What is the difference between conductive hearing loss and sensineural hearing loss?
Sensineural loss invovles both bone conduction and air conduction resulting in complete deafness. Conductive just deals with problems trasfering air waves to mechanical and fluid waves. Usually the ossicles are involved or there is some type of infection.
What is the Weber Test and how can it tell the difference between conductive hearing loss and sensineuronal hearing loss?
It tests the bony conduction using vibration with a tuning fork on the forehead.
Conductive hearing loss presents with a louder sound in the affected ear.
Sensineuronal hearing loss presents with louder sound in the normal ear.
Describe the Rinne Test.
Compares bone and air conduction. A tuning fork is placed on the mastoid process. Once the patient can no longer hear the sound from the fork, it is then moved by the ear to test air conduction. In a normal patient they should be able to hear the fork vibrating.
With conductive hearing loss the patient will be able to hear the fork when it is on the mastoid process but not when it is by the external auditory meatus.
