Auditory Flashcards
(29 cards)
Human speech intensity
65dB
Frequency
10-20,000Hz
What occurs in the middle ear?
air pressure waves are converted to mechanical energy via tympanic membrane and ossicles
Tube responsible for connecting ear with nasopharynx
Eustachian tube (site of infections known as otitis media)
Function of tensor tympani
pressure regulator; stretched in loud environment (innervated by CN 5)
Function of stapedius
purely reflexive, contracts to dampen very loud sounds by pulling on neck of stapes to control amplitude of sound (innervated by 7)
What can you see past the tympanic membrane?
CN 7 and malleus
Two components of inner ear
cochlea and vestibular apparatus (semicircular canals, etc)
Perilymph
fluid in bony labyrinth
Endolymph
fluid in membranous labyrinth; has very little protein and very low sodium concentration; carries a charge of +80mV
Three routs of pressure wave transduction to inner ear
1) Air (poor)
2) Osseous (vibration of bone in skull - mastoid and petrous - still poor) called bone conduction
3) Ossicular (EFFICIENT) directly couples inner and outer ear; called air conduction
What makes up the cochlea?
scala vestibuli (connected to oval window), helicotrema (apex), and scala tympani (connected to round window)
What secretes endolymph?
stria vascularis
What is cochlea contained within?
the modiolus
What structure is between the scala vestibuli and scala tympani?
Cochlear duct (scala media)
Reisner’s membrane separates it from scala vestibuli from above
Basilar membrane separates it from scala tympani from below
Where is the basilar membrane the widest?
helicotrema (the apex)
low pitches heard here
Where is the basilar membrane the stiffest?
at the base
highest pitches are heard here
What is the Organ of Corti?
site of transduction of pressure waves on the hair cells - sits on the basilar membrane
Function of outer hair cells
- displacement sensitive
- used to modulate the tectorial membrane (ONLY receptors directly modified by CNS and can tune themselves to respond by becoming longer and shorter)
- 10 hair cells per bipolar cell
Function of inner hair cells
- velocity sensitive
- short and stiff and used to detect sound; NOT modified by CNS
- each are innervated by 10 bipolar cells
What does bending of the hair cells TOWARDS kinocilium do?
depolarizes and opens K+ ion channels
What does bending of hair cells AWAY from kinocilium do?
hyperpolarizes and closes K+ channels decreasing release of neurotransmitter
What is the “Tonotopic Map?”
map of basilar membrane where different frequencies resonate along it. Info is carried to CNS (like cochlear nuclei, inferior colliculus, medial geniculate, cerebral cortex, and Heschel’s gyrus)
Where is hearing bilateral?
past cochlear nuclei