auditory system Flashcards
external ear
collects sound waves and channels them inwards
- the auricle
- the external auditory canal
- the tympanic membrane
middle ear
conveys signals to the oval windows
- the temporal bone
- the oval window
- the round window
inner ear
contains the receptors for hearing and equilibrium
the tympanic membrane
- eardrum
- separates the external canal and the middle ear
ceruminous glands
- located near the exterior opening of the external canal
- help prevent dirt and foreign objects from entering the ear
auditory ossicles
- the middle ear
- the malleus
- the incus
- the stapes
Malleus
- “the handle” attaches to the internal surface of the tympanic membrane
- “the head” of the malleus forms a joint with the incus
Incus
- incus joins with malleus joins into the oval window.
tensor tympani and stapedius
- tiny skeletal muscles attached to the auditory ossicles
TT = limits movement and increases the tension of the tympanic membrane to prevent damage from loud noises
Stapedius = dampen large vibrations of the stapes due to loud noises and protects the oval window from damage
eustachian tube
- connects the middle ear to the nasopharynx
inner ear
- bony labyrinth - outer - fluid - perilymph
- membranous labyrinth - inner - fluid = endolymph
Bony labyrinth
- semi-circular channels
- the vestibule
- the cochlea (the cochlea duct, the vestibular membrane and tympanic membrane).
organ of corti
- rests on the basilar membrane
- ## has hair cells (receptors for hearing that extend onto the cochlea duct)
tectorial membrane
- protects over and makes contact with the hair cells of the spiral organ
auditory nerve stimulation
- sound waves arrive at the tympanic membrane
- movement of the tympanic membrane causes displacement of auditory ossicles
- movement of the stapes at the oval window establishes pressure waves
- the pressure waves distort the basilar membrane on their way to the round window of the tympanic duct.
- Vibration of the basilar membrane causes vibration of the hair cells against the tectorial membrane.
- Info. is sent to CNS
frequencies in the basilar membrane
- changes wider/flexible at one end to narrow/shift at the other end.
- narrow = high frequencies
- wider cells = low frequencies = hair cells
static equilibrium
refers to the maintenance of body position relative to the force of gravity
dynamic equilibrium
- maintenance of body position in response to rotational movements
receptor organ for dynamic
vestibular apparatus
receptor for static
macula - a thickened region in utricle and saccule in vestibular apparatus
hair cell
sensory receptors that detect changes in head position
supporting cells
surround hair cells - provide structural and chemical support
- secrete gelatinous substance that forms the otolithic membrane
Otoliths
- crystals of calcium carbonate on the otolithic membrane
- add weight to the membrane and increase the influence of gravity during movements
how the head tilts backwards
- otolithic membrane slide down due to gravity
- bends the microvilli that farm hair bundles
- opens up ion channels, resulting in a depolarising graded potential in the hair cells
- cause the release of neurotransmitters
semicircular duct
- arranged each loop lies at right angles at each other and allows it to detect rotational movement of head
ampulla
- semicircular duct
- receptors of rotational movement
- includes the crista - hair cells
copula
- membrane extends over the crista
- the microvilli that makeup hair bundles of hair cells project into the copula
when you tilt your head side to side
- hair cells don’t move
- the endolymph in the semicircular duct moves = pushes on the cupula = bends the hair cells, opening ion channel and causing depolarisation and neuro transmitting.
