1.52 The Auditory Pathway Flashcards
What is frequency?
Pitch of sound; measured in Hz cycles per second
What is amplitude?
Intensity - Loudness - measured in dB - log scale - because it can detect very wide range of sound pressure
How many hair cells are in contact with one auditory fibre?
One hair cell = one auditory nerve
As the sound gets louder, what happens to the number of frequencies the auditory nerve responds to?
Higher range of frequencies as sound gets louder
Which frequency is the auditory nerve most sensitive to?
Peak of graph - still picked up at a low sound level
What happens when the outer hair cell amplifier gets damaged?
Fibre less sensitive - peak lower on graph - poorer tuning - the sound needs to be louder to be heard, peak is at a lower frequency - high frequency lost
Explain the tonotopic organisation of the ear…
The auditory system keeps track of where information originated on the basilar membrane - map of frequency all the way to the auditory centre. (sound and place = tonotopic)
What is phase locking?
Synchronisation of action potential firing to peaks in waveform of low frequency (
What is the equation for frequency?
freq=1/t
Explain the auditory pathway…
Cochlea Auditory nerve Cochlear nuclei - first synapse (ventral) - pontomedullary junction Some Cross at olivary complex Superior olive Lateral lemniscus Inferior colliculus Medial geniculate body thalamus Auditory cortex - temporal lobe
Where is the auditory cortex located?
Temporal lobe - inferior to sylvian fissure - Heschles gyrus
What does dysohasia mean?
Deficits in language
Which parts of the brain are responsible for language production and comprehension?
Wernicke’s - comprehension
Broca’s - production
How is sound localised in low frequencies?
Sounds in different positions in space lead to freeness in timing and intensity - inter aural differences - for low frequencies where waves are long
How is sound localised in high frequencies?
Head casts a shadow high frequencies - brain detest difference in sound between ears
What is responsible for conductive hearing loss?
Middle ear
Infection - otitis media
Otosclerosis - ossicular chain stiffens
What are the sensorineural causes for hearing loss?
Loss of hair cells or damage to nerve connections - loss of volume and resolution - social isolation
Majority is genetic asymptomatic
What are the central causes for hearing loss?
Following stroke - word deafness - auditory verbal agnosia
What could Usher’s syndrome; Waardenburg syndrome; mitochondrial disorders all cause?
Sensorineural hearing loss
What is a cochlear implant…
Induction coil transmits across scalp and skull
Electrode stimulates the nerve fibres in the cochlear
