Unit 5 Lecture 39 Flashcards
What structures make up the external ear?
- Auricle
- External auditory canal
- Eardrum (tympanic membrane)
What structures make up the middle ear?
- Auditory tube
- Auditory ossicles
What structures makes up the inner ear?
- Semicircular ducts
- Utricle
- Saccule
- Cochlea
What are the semicircular ducts responsible for?
equilibrium and balance
What is the cochlea responsible for?
Hearing
What is the saccule responsible for?
Gravity and acceleration
Steps of hearing?
- Sound waves arrive at tympanic membrane
- Vibrations moves auditory ossicles
- Stapes depresses oval window -> generates pressure wave in cochlear ducts
- Pressure wave distorts basilar membrane (different regions by different wavelengths)
- Vibration of basilar membrane excites overlaying hair cells (produces receptor potentials)
What is paralymph?
Like CSF
What is endolymph
extra cellular fluid that’s high in K+
Where is endolymph found?
Cochlear duct
What is the purpose of hair cells?
They act as receptors for hearing and balance/equilibrium
What is the cilia on hair cells called?
stereocilia
Define stereocilia
Mechano-sensing organelles on hair cells that move to fluid motion in the ear
(fluid = enyolymph)
What type of ion channels are found on stereocilia?
Mechanically gated ion channels
Define mechanically gated ion channels
Ion channels that open when the membrane is stretched
How is the receptor potential changed in the ear?
- Endolymph hits and MOVES the hairs in the cochlear duct
- Mechanically gated ion channels on the stereocilia OPEN
- K+ in endolymph goes INTO the cell
- DEPOLARIZATION
Steps of auditory transduction
- waves in cochlear
- moves hairs
- opens mechanically gated channels on stereocilia
- K+ into cell -> DEPOLARIZATION
- Ca+ channels open at base of hair cell
- Ca+ -> neurotransmitters and depolarization of VIII nerve
What causes the most and least damage to hair cells
least = rustling leaves
most = headphones
What controls equilibrium and balance?
Semicircular ducts
What are the 3 semicircular ducts?
Anterior, posterior and lateral
What is found at the base of each duct?
Ampulla
What is the ampulla?
the enlargement at the base of each semicircular duct
What is found within each ampulla?
Crista
What is the crista?
“bundle” of hair cell complexes
What is the purpose of the crista?
Senses rotational movements of the head
What controls the sense of gravity and acceleration?
Hairs in the UTRICLE and SACCULE
What activates the hair cells in the utricle and saccule?
Otoliths
What is otoliths?
particles in the fluid found in the utricle and saccule
What head movement stimulates the movement of otoliths?
up and down
What head movement stimulates the movement of crista?
Side to side
