hearing and equilibrium Flashcards
what is hearing
Auditory system
response to vibrating air molecules
what is equilibrium
Vestibular system
sense of motion & balance
what is sound
Pressure wave
zone of compression (air particles close together) & zone of rarefaction (air particles spread apart)
what is pitch (high or low)
frequency of vibration [Hz]
what is loudness
amplitude of vibration [Db]
what is pitch measured in
hertz (Hz)
what is loudness measured in
decibels (Db)
explain the outer ear
fleshy auricle/pinna; auditory canal
secretions + dead cells
- earwax
explain the middle ear
eardrum; 3 smallest bones & 2 smallest skeletal muscles of body
contains auditory ossicles:
- Malleus [hammer]
- Incus [anvil]
- Stapes [stirrup]
explain the inner ear
bony labyrinth contains:
Organs of equilibrium
Organ of hearing
- cochlea
in the anatomy of the ear, the eustachian tube leads to what
to nasopharynx (superior portion of pharynx)
where does ear wax come from
from ceruminous glands in outer ear canal
what is the eustachian tube
(auditory tube)
is an air circulating tube which goes from back of nose, near the adenoids, to the air space in the middle ear
what does an air pressure equalization tube do
keep middle ear pressure the same as outside pressure
explain the cochlea in the inner ear
Snail-like spiral with 3 fluid filled chambers
Vibration form a nerve impulse via organ of corti.
explain the organ of corti
Contains outer hair cells with hairs
- stereocilia
On top of which rests gelatinous tectorial membrane
Base of cell synapses with nerve fibres
explain how the organ of corti allows us to hear
Sound bends hairs (via vibrating membranes & lymph)
to
Depolarise cell
to
Induces action potential
to
Conducted to CNS
to
Translated in cerebral cortex as ‘sound’
The cochlea is filled with what and what doe sthis do
a fluid
moves in response to the vibrations from theoval window.
As the fluid moves, 25,000 nerve endings are set into motion.
These nerve endings transform the vibrations into electrical impulses, these travel along the eighth cranial nerve to the brain
- auditory nerve
describe the Frequency Response of Basilar Membrane of Cochlea
Low pitch in centre, high pitch as enter cochlea:
explain the vestibular system
Human Labyrinth, from the left ear. It contains i) the cochlea (yellow), which is the peripheral organ of our auditory system; ii) the semicircular canals (brown), which transduce rotational movements; and iii) the otoliths (in the grey pouches), which transduce linear accelerations. The light blue pouch is the endolymphatic sac and contains only fluid.
name the semi circular canals part of the vestibular apparatus
anterior
posterior
horizontal
and these are all on the lateral part of the ear
name the otolith organs canals part of the vestibular apparatus
utricle
saccule
cochlea
and these are all medial to the ear
semicircular ducts are stimulated by what
by rotation of head in different planes
semi circular ducts are filled with what
endolymph
what does each of the semicircular ducts have at one end
dilated sac at one end called:
Ampulla
describe the structure and cells of semicircular ducts sac’s
With mound of hair cells with stereocilia embeded in gelatinous cupula membrane; all called crista ampullaris
how do semicircular canals move
by cupula being pushed over as head turns
this is called: Crista ampullaris
what does equilibrium provide us with
co-ordination of balance
explain the vestibular apparatus in terms of equilibrium
Contain structures and receptors for equilibrium
3 semicircular canals/ducts:
- movement e.g., rotation
2 chambers:
- Otolith organs; saccule & utricle
— position, acceleration or deceleration
what are the 2 types of equilibrium called
static
dynamic
what is static equilibrium
head orientation when stationary
what is dynamic equilibrium
motion or acceleration
explain the chambers of the vestibular
Each chamber has patch of hair cells:
Macula
- 1 vertical = macula sacculi
- 1 horizontal = macula utriculi
With stereocilia tips embedded in gelatinous otolithic membrane
Weighted with otoliths
- calcium carbonate-protein crystals
what do otoliths do
bend hairs
name the 2 auditory neural pathways
peripheral auditory canal (outer, middle and inner ear)
central auditory system (auditory cortex, medial geniculate body (parts of brain), inferior colliculus (within chest), cochlear nucleus, superior olivary complex(stomach and pelvis area))
explain the CNS pathway for equilibrium
in vestibular apparatus:
vestibular branch of bestibulocochlear nerve (Viii)
then to vestibular nuclei of medulla and then to somatic motor neurons controlling eye movement
or
from vestibular apparatus to cerebellum then reticular formation, then to thalamus, and then to the cerebral cortex in the brain
