N18 auditory system Flashcards
define hearing
neural perception of sound energy
Define sound
audible distrubance of molecules in a medium eg air or water
describe sound waves
longitudinal waves
frequency - pitch
amplitude - volume
what is the audible range?
20 hz - 20 kHz
give a brief description of external ear and list its contents
external - Air - collection
- EAM
- auricle
give a brief description of the middle ear and list its contents
Middle - bone - concentration oval window round window malleaus, incus and stapes nasopharyngel tube
give a brief description of inner ear and list its contents
cochlea
internal auditory meatus
what type of joints are between the middle ear bones?
synovial
how are vibrations created in the perilymph?
stapes rock back and forth on oval windows to create vibrations on perilymph
inner ear - cochlea
how are vibrations reach oval window?
vibrations detected and travel through perilymph to round window
how are vibrations transferred across the ear?
via the three ear bones
malleus
incus
stapes
which labyrinth contains perilymph?
bony
which labyrinth contains endolymph?
membranous
structure of the cochlea
3 tubes running through ;
scala tympani
scala media
scala vestibule
helicotrema is the tip
organ of Corti is within the scala media
what does the tectorial membrane have resting on it?
inner and outer hair cells
what is the function of outer and inner hair cells?
outer - vibration of hair cells increase to increase movement
inner - you can only hear with inner hair cells
what is the function of the Organ of Corti?
detects soundwaves produced in the fluid in the cochlea by vibration of the stapes and sends action potentials centrally in the cochlear division of the vestibulocochlear
what are the sensory cells?
hair cells
which fluid is present in the scala media and duct?
endolymph
define tonotopicity
- high tones are transmitted at beginning of cochlear swirl and low tones are transmitted at tip
describe the neural pathway
dorsal and ventral cochlea nuclei
22 describe the neural pathway superior olivary nuclei (synapse) inferior colliculus (3rd neuron) medial geniculate body in the thalamus goes up to internal capsule into auditory radiation into the primary auditory cortex which sits on the superior auditory temporal lobe
to knock out hearing completely what would have to happen?
you would have to knock out the entire brainstem as it ascends bilaterally
what is the bundle of sensory fibres that travel from superior olivary nuclei to inferior colliculus
lateral lemniscus
what is the function of the superior olivary nucleus
timing of sound waves ie knows where to look when someone clicks - left or right
what is the function of semi-cricular canals?
filled with endolymph
lined with cilia
endolymph moves the cila - as a result brain knows how to keep the body balanced
what does the utricles, saccule within the vestibule respond to?
changes in position of head with respect to gravity
ex) if head moves left there is increased firing from left semicircular ducts and decreased firing from right semicircular ducts
describe the 3 vestibular pathways
1) vestibular ganglion –> nerve –> spinal cord in vestibulospinal tract
2) vestibular ganglion –> nerve –> vestibular nuclei –> medial longitudinal fasiculus
3) vestibular ganglion –> nerve –> vestibular nuclei –> thalamus –> cortex/ cerebellum
what is the sensory plaque called in saccule and utricle?
macula - detect linear acceleration/ head position
hair cells in vestibular apparatus are different from trochlea?
true as they have a baseline activity - constantly sending impulses
how do we sweep our eyes?
vestibulo - ocular reflex
vestibular nuclei communicates with abducens (LR6)
and oculomotor (AO3) through the medial longitudinal fissure speaks to 3,4,6 …
