Physiology Of Hearing Flashcards
Travelling speed of sounds?
340m/s
What is intensity measured in?
dB SPL
What is pain threshold?
140db spl
Frequency range for adult humans?
20 to 20,000
Over which level can you get permanent hearing damage?
Over 90 db
What are 3 bones inside middle ear cavity?
Incus, malleus, stapes
How much pressure is increased in middle ear?
X45
Otitis media?
Infection/ inflammation of middle ear, in children (upper respiratory tract infection), fills with fluid
Grommets?
Small tube placed in ear for drainage
Otosclerosis?
Fusion of stapes and oval window
Frequency at basal end?
High
Frequency apical end?
Low
Scala vestibule is connected to?
Oval window
Scala tympani is connected to?
Round window
Where do scala vestibule and tympani communicate?
Helicotrema at apex of cochlear
What do scala vestibule and tympani contain?
Perilymph high sodium low potassium
What does scala media contain?
Endolymph
Where is endolymph produced?
Stria vascularis
What does round window act as?
Pressure relief, bulges out so fluid doesn’t get compressed
What does organ of corti do?
Detects sound induced motions of basilar membrane
Hair cells are between?
Tectorial and basilar membrane
Apical membrane of hair cells is in?
Endolymph
Basolateral membrane is bathed in?
Perilymph
How many hair cells in human cochlea?
15,000
What causes mechano-electrical transducer channels to open?
Tips links pulls open in direction of excitation
When outer hair cells depolarise and hyperpolarise what happens?
Depolarise-shorten
Hyperpolarise-lengthen
Prestin in basolateral membrane, OHC motor, a modified anion exchanger
Inner hair cells are innervated by?
10-20 type 1 spinal neurons
Outer hair cells are innervated by?
Type 2 spinal neurons, painfully loud sound
Efferent fibres from medial olive innervated?
Outer hair cells
Efferent fibres from lateral olive synapse on?
Type 1 afferent fibres
Cochlear ganglion transmits afferent information via which nerve?
8th
Noise can cause what?
Glutamate excitotoxicity
Mitochondrial damage
Physical effects of hair bundle
How many people over 70 have significant hearing loss?
30%
Ototxic drugs?
CispLatin, loop diuretics,aminoglycoside antibiotics salicylate
Genetic mutation?
1 in 2000
How many deafness genes?
More than 50
Which genes are affected in congenital deafness?
50% in gap junction genes
Maximum channels in cochlear implants?
24
Central auditory system?
Can’t stop needing info, must proceed
Cochlear nucleus Superior Olivary complex Nucleus of lateral leminiscus Inferior colliculus Medial geniculate body Primary auditory cortex
What does superior olivary complex do?
Localise sound in space
Interaural level difference?
Sound intensity in lateral superior olive
Interaural time difference?
Medial superior olive- timing of arrival of sounds in left and right ears
Inferior colliculus?
Laminar organisation, isofrequency sheets.
Combine complex frequency and amplitude analysis of dorsal cochlear nucleus and sound localisation from superior olivary nucleus
Reflex centre
Lesions in auditory cortex cause?
Sound localisation, discrimination of temporal pattern, intelligibility of speech
What are the targets of deafness genes in the cochlea?
Tight junctions Transduction complex Gap junctions Afferent synapse Tectorial membrane Stria vascularis
What is motor aphasia?
Brocas
What is sensory aphasia?
Wernickes