Auditory Senses Flashcards
What are the bones of the middle ear? And the correct sequence
Tympanic membrane before first ossicle
Malleus
Incus
Stapes
Last ossicle conects with the oval window
What are the muscles of the middle ear and their function?
Tensor tympani – inserts on the malleus and pulls handle of malleus inward
Stapedius – inserts on the stapes and pulls stapes outward
These muscles contract reflexiviely in response to loud sounds
What is impedance matching? What structures are responcible for it?
Amplification of vibrations on the typmanic membrane, through the ossicle system to cause vibration in the fluid of the cochlea (by 22X) - between air and fluid
Tympanic membrane and auditory ossicles
What are the major components of the cochlea?
Scala vestibuli
Scala media
Scala tympani
Reissner’s membrane
How do Reissner’s membrane and Basliar membrane relate to the tubes of the cochlea (scala media, scala vestibuli and scala tympani)?
Reissner’s membrane seperates the scala vestibuli from the scala media
Basliar membrane speerates the scala media from the scala tympani
-organ of corti sits on the basliar membrane
What is the function of Reissner’s membrane?
Seperates a special fluid within the scala media and away from the scala vestibuli
Basilar Fibers, what’s the pattern in the cochlea and how do they pick up different frequencies?
Length of the fibers/hairs increace from the oval window to the apex of the cochlea. Diameter decreases from oval window to apex
Stiff short fibers: near oval window -> high freqency
Long, limber fibers: near apex -> low frequency
What is the organ of corti? What are it’s sensory receptors?
It generates nerve impulses in response to vibration of the basilar membrane
Sensory receptors are hair cells
- single row of internal
- 3-4 rows of external
Endolymph and Perilymph, where are they found? What’s the difference between the two? What does this create?
Scala Media has endolymph
Scala tympani and scala vestibuli has perilymph
Endolymph has a high conc of K+ and a low conc of Na+, perilymph has the opposite
Create and endocochlear potential where theres +80mV difference between the two fluids
What is the place principle?
The nervous system detects sound frequencies by determining positions along the basilar membrane that are most stimulated
What is the mechanism which polarized hair cells on the organ of corti?
The inner and outer hair cells have stereocilia in the tectorial membrane
Hair cells are then attached to reticular lamina on the other side, which is supported by rods of corti and connected to the basilar fiber.
When the basilar fiber moves everything else moves and bends the hair cells
One direction polarizes them, other hyperpolarizes
What is a decibel
.sound energy measured in bel, 0.1 bel is a decibel
One decibel is an increase of 1.26 times
What are the components of the auditory transmission pathway?
.spiral organ of corti Dorsal and ventral cochlear nuclei Superior olivary nuceus Lateral lemniscus nucleus Medial geniculate nuleus in the thalamus Auditory cortex
Where does decussation occur in the auditory pathways (between left and righ)
decussation between the dorsal and ventral cochlear nucleus and the superiory olivary nucleus
What is the relationship of the auditory tracts and the RAS?
.many collateral auditory tracts go through the RAS and respond to sudden or loud noises
