Module 7: Sensory System pt.2 Flashcards
the auditory system – structure
External ear (contains ear or auricle and external ear canal)
Middle ear(eardrum (tympanic membrane), ear ossicles (3 bones – malleus, incus, stapes), and the eustachian tube)
Inner ear (vestibular apparatus (involved in balance) and cochlea (process sound)
…
External auditory canal
Tympanic membrane (eardrum)
Ear ossicles
Vestibular apparatus
Cochlea
Eustachian tube
Oval window
small membrane covered opening directly underneath the stapes (one of the ear ossicles)
structure of the cochlea
Snail
Three compartments, separated with basilar membrane:
- Scala vestibuli (upper) also vestibular duct
- Middle cochlear duct
- Lower scala typani
*Basilar membrane contains organ of Corti
- Where sound is converted to action potentials
- Hair cells embedded in tectorial membrane
(Hair cells bend)
organ of Corti
- Where sound is converted to action potentials
- Hair cells embedded in tectorial membrane
(Hair cells bend)
Frequency
waves/time
Intensity
amplitude of wave
transfer and amplification of sound vibrations
Sound waves reach ear
Sound waves funneled into the external auditory canal
Sound waves strike tympanic membrane (causing it to flex back and forth
Levering action of ear ossicles amplifies pressure of waves that strike the tympanic membrane
Ear ossicles cause oval window to vibrate (oval window is much smaller since the ear ossicles amplify the sound 15-20X their original height)
Perilymph (Fluid in cochlea) transmits waves to hair cells in basilar membrane
Hair cells detect vibrations and turns them into action potentials in the auditory nerve
basilar (basement) membrane
Wide and thin at top of cochlea, loose tension (Low freq)
Narrow and thick at base near the oval window, tight tension (High freq)
Tention also varies
Length and stiffness of hairs differ slightly
how we hear / sound
Basilar membrane vibrates
Hair cells are bent
Ion channels open
Depolarization of cells occurs
Depolarization releases a NT from hair cells which Excites neurons of auditory nerve (fired APs)
- Lounder the sound = stronger vibration = more bent cells = more NT released and high freq of AP produced
Signals flow to auditiry cortex (in temporal lobe)
the vestibular system
Located in inner ear next to cochlea
Maintains balance, equilibrium, posturnal reflexes
- Detects linear and rotational motion and position of head relative to rest of body
Also: eye movement vestibular ocular reflex (VOR)
structure of the vestibular apparatus
2 primary structures
Semicircular canals (detect rotational&angular accelerations of head)
Otolith organs (detect linear accelerations)
3 semicircular canals
Each detect movement in each plane of motion
2 otolith organs
Utricle – horizontal accelerations&decelerations
Saccule – vertical accelerations&decelerations
enolymph
Semicircular canals are filled with fluid that fluid - enilynoh
ampula
At end of each semicircular canal = swelling
whats in the ampula
sensory region (crista ampullaris)
sensory region (crista ampullaris) contains what
Crista ampullaris contains sensory hair cells (fixed at the base, their cilia embededd in gelatious material – cupula)
hair cells depolarize
Endolymph lags behind (seems to move right)
Endolymph hits cupula and bends hair cells
When hair cells are bent a certain way, they depolarize and send AP to brain
When bent other way, they hyperpolarize (no AP)
otolith hair cells
Anchored at base
Have cilia embedded in a gelatinous membrane
Gelatinous membrane has otolith crystals embedded in it to give it weight and inertia during movements
rest - what happens hair cells otolith organs
AP produced reg.
move - what happens hair cells otolith organs
otolith crystals lag behind and seem to move in the opposite direction of the acceleration
Bends cilia of hair cells in opp direction
Causes them to increase frequency of AP in vestibular nerve
constant velocity - otolith crystals lag behind and seem to move in the opposite direction of the acceleration
Bends cilia of hair cells in opp direction
Causes them to increase frequency of AP in vestibular nerve
hair cells move back to resting state
hair cell bent toward or away kinocelia describe what happens
Stereocilia bent toward kinocilia – increase frequency of action potential
Stereocilia bent away from kinocelia - decrease frequency of action potentials
