Physiology of hearing Flashcards
What are some functions of hearing
alerting to dangers, localizing objects, recognition, and communicating via speech.
What is sound
Pressure waves that travel through the air at 340m/s.
list the components of the peripheral auditory system
the outer ear, middle ear, cochlea, and auditory nerve
outline the middle ear
known as the impedance matching device: increases pressure by around x45 and prevents sound from being reflected back from the fluid-filled cochlea.
What are some problems that can occur in the middle ear
otitis media: infection or inflammation of the middle ear, common in children (often from the upper resp tract infection), glue ear (may need draining).
otosclerosis: occurs from the fusion of stapes with oval window and can be fixed by surgery.
Outline the parts of the cochlea
There is a basal end (tuned to high freq sounds),
there is an apical end (tuned to low freq sounds).
What are the 3 components of the cochlea
The scala vestibuli, scala media and scala tympani
What is the composition of the cochlear fluids
the scala vestibuli and scala tympani contain perilymph and the scala media contains endolymph
What is the organ of corti
The part of the inner ear that contrains the hair cells, the inner hair cells and outer hair cells.
how are the inner hair cells innervated
innervated by afferent nerve fibres and outer hair cells are mainly innervated by efferent nerve fibres.
How do hair cells process sound
Hair cells have hair bundles which move and open non selective cation channels and pottasium enters and depolarises the hair cell and causes VGCa channels open and calcium ions trigger vesicle release and afferent nerve fibres are activated
What effect does depolarisation have on hair cells
depolarisation: shortens, hyperpolarisation: lengthens.
What are the common causes of sensioryneural hearing loss
Noise ( affects hair bundles, mitochondrial damage etc)
ageing ( hair cells, cochlear ganglion etc degrade)
ototoxic drugs ( cisplatin, loop diuretics, salicylate etc)
genetic mutations
What are some of the targets of deafness genes in the cochlea
tight junctions, gap junctions, afferent synapse, transduction complex, stria vascularis, tectorial membrane and afferent synapses.
Outline cochlear implants
surgically implanted electronic device that provides sense of sound to a person who is profoundly death.
it is very expensive and it results often good enough to recognise and comprehend speech.
state the different levels of the central auditory system
starts at cochlear nucleus, sup olivary complex, muclei of lateral leminiscus, inferior colliculus to medial geniculate body and primary auditory cortex
What occurs in the cochlear nucleus
parallel processing of sound starts to occur,
What occurs in the superior olivary complex
helps localise sound in space and to do this you use two main cues: uses both ears and its called the bineural cues. interaural level differences (detected in lateral sup olive) and interaural time differences ( medial sup olive).
What occurs in the inferior colliculus
organised in laminar fashion, combines complex frequency and sound localisation from SOC.
outline the the auditory cortex
the primary auditory cortex is located on the upper surface of the temporal love, lesions in auditory cortex cause defects in: sound localisation, intelligibility of speech etc. lesions in brocas area indicates: motor aphasia ( hard to produce sound) and in wernickes area: sensory aphasia (production and comprehension of speech)
