Physiology of hearing

Question 1

What are some functions of hearing

Answer 1

alerting to dangers, localizing objects, recognition, and communicating via speech.

Question 2

What is sound

Answer 2

Pressure waves that travel through the air at 340m/s.

Question 3

list the components of the peripheral auditory system

Answer 3

the outer ear, middle ear, cochlea, and auditory nerve

Question 4

outline the middle ear

Answer 4

known as the impedance matching device: increases pressure by around x45 and prevents sound from being reflected back from the fluid-filled cochlea.

Question 5

What are some problems that can occur in the middle ear

Answer 5

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.

Question 6

Outline the parts of the cochlea

Answer 6

There is a basal end (tuned to high freq sounds),

there is an apical end (tuned to low freq sounds).

Question 7

What are the 3 components of the cochlea

Answer 7

The scala vestibuli, scala media and scala tympani

Question 8

What is the composition of the cochlear fluids

Answer 8

the scala vestibuli and scala tympani contain perilymph and the scala media contains endolymph

Question 9

What is the organ of corti

Answer 9

The part of the inner ear that contrains the hair cells, the inner hair cells and outer hair cells.

Question 10

how are the inner hair cells innervated

Answer 10

innervated by afferent nerve fibres and outer hair cells are mainly innervated by efferent nerve fibres.

Question 11

How do hair cells process sound

Answer 11

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

Question 12

What effect does depolarisation have on hair cells

Answer 12

depolarisation: shortens, hyperpolarisation: lengthens.

Question 13

What are the common causes of sensioryneural hearing loss

Answer 13

Noise ( affects hair bundles, mitochondrial damage etc)
ageing ( hair cells, cochlear ganglion etc degrade)
ototoxic drugs ( cisplatin, loop diuretics, salicylate etc)
genetic mutations

Question 14

What are some of the targets of deafness genes in the cochlea

Answer 14

tight junctions, gap junctions, afferent synapse, transduction complex, stria vascularis, tectorial membrane and afferent synapses.

Question 15

Outline cochlear implants

Answer 15

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.

Question 16

state the different levels of the central auditory system

Answer 16

starts at cochlear nucleus, sup olivary complex, muclei of lateral leminiscus, inferior colliculus to medial geniculate body and primary auditory cortex

Question 17

What occurs in the cochlear nucleus

Answer 17

parallel processing of sound starts to occur,

Question 18

What occurs in the superior olivary complex

Answer 18

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).

Question 19

What occurs in the inferior colliculus

Answer 19

organised in laminar fashion, combines complex frequency and sound localisation from SOC.

Question 20

outline the the auditory cortex

Answer 20

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)