special senses: auditory Flashcards
Soundwaves have two components:
- Frequency (number of waves over time) – perceived as pitch
ex: high pitch like a whistle= high frequency
2.Amplitude (height of sound wave) – perceived as loudness
shouting= high amplitude
structure of ear: pinna
directs soundwaves into the ear canal.
structure of ear: ear canal
carries soundwaves to the tympanica
membrane (ear drum). Tympanic membrane vibrates with the same frequency and amplitude as the sound you hear.
structure of ear: tympanica
membrane
ear drum
structure of ear: Middle ear ossicles
transmit vibrations from the tympanic membrane to the inner ear
structure of ear: Malleus
connected to tympanic membrane
structure of ear: Stapes
connected to oval window (thin membrane that separates inner ear from middle ear)
where do vibrations pass through (MIT)
Vibrations pass from malleus to incus to stapes – and stapes vibrates against the oval window
Inner ear: Vestibular apparatus
For equilibrium
Inner ear: Cochlea
For hearing
inner ear: 3 fluid channels (vtc)
vestibular duct
tympanic duct
these 2 filled with perilymph – similar composition to extracellular fluids)
cochlear duct
cochlear duct filled with:
filled with endolymph = similar
to intracellular fluid with high [K+], low Na+
what creates waves in the fluids inside the 3 ducts.
Vibration of stapes on oval window
Cochlear duct and tympanic duct are separated by
basilar membrane which plays a role in the coding of pitch
(think CT basel membrane)
Cochlear duct: Tectorial membrane
waves in perilymph of vestibular
duct cause this membrane to move and bend hair cells
Cochlear duct: hair cells
non-neural mechanoreceptor cells for hearing
Have stereocilia (hair-like structures) that are embedded in tectorial membrane (range in different heights)
tallest stereocilium is called the
klinocilium
When stereocilia are physically bent in the direction of the klinocilium by movement of tectorial membrane or basilar membrane, signal transduction occurs and they release
neurotransmitter onto the primary auditory neurons
Labelled line coding likely determines
The frequency of action potentials to the brain, determines
pitch
sound intensity (loudness).
conductive hearing loss
-Sounds cannot be transmitted (conducted) through the middle ear
conductive hearing loss cause
Ear canal plugged with earwax or foreign object
Fluid in or damage to middle ear that prevents middle ear ossicles from vibrating
what happens in conductive hearing loss
Makes sounds louder in the the affected ear.
Hair cell receptors and cochlear nerve still intact and and can detect soundwaves through vibration of the
bones of the skull in which the cochlea is embedded
Sounds are not dulled by other ambient sounds, as they would be if sound was being conducted through
the middle ear
ex: covering one ear while talking stimulates conductive hearing loss
central hearing loss
Results from damage to nerve pathways leading to the auditory cortex (rare)
Makes sounds louder in the the unaffected ear since there is no transmission of signals into the cortex
Sensorineural hearing loss
Results from damage/death to hair cells
causes:
-aging
-Chronic exposure to loud noises
- Makes sounds louder in the unaffected ear since there
is impaired transmission of signals from receptors to the neurons they stimulate
Vestibular apparatus
provides information
about movement and position of the body.
Vestibular apparatus consist of… (sus)
Saccule, Utricle (Sense linear movements and head position)
and Semicircular canals sense rotational movements (help
you keep balance when spinning)
Each structure in the vestibular apparatus contains
hair cells (similar to those in the cochlea) that are activated
as a result of change in position and/or movement Sense linear movements and head position
