Module 7: Sensory System pt.2

Question 1

the auditory system – structure

Answer 1

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

Question 2

Oval window

Answer 2

small membrane covered opening directly underneath the stapes (one of the ear ossicles)

Question 3

structure of the cochlea

Answer 3

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)

Question 4

organ of Corti

Answer 4

• Where sound is converted to action potentials
• Hair cells embedded in tectorial membrane
  (Hair cells bend)

Question 5

Frequency

Answer 5

waves/time

Question 6

Intensity

Answer 6

amplitude of wave

Question 7

transfer and amplification of sound vibrations

Answer 7

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

Question 8

basilar (basement) membrane

Answer 8

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

Question 9

how we hear / sound

Answer 9

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)

Question 10

the vestibular system

Answer 10

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)

Question 11

structure of the vestibular apparatus

2 primary structures

Answer 11

Semicircular canals (detect rotational&angular accelerations of head)

Otolith organs (detect linear accelerations)

Question 12

3 semicircular canals

Answer 12

Each detect movement in each plane of motion

Question 13

2 otolith organs

Answer 13

Utricle – horizontal accelerations&decelerations

Saccule – vertical accelerations&decelerations

Question 14

enolymph

Answer 14

Semicircular canals are filled with fluid that fluid - enilynoh

Question 15

ampula

Answer 15

At end of each semicircular canal = swelling

Question 16

whats in the ampula

Answer 16

sensory region (crista ampullaris)

Question 17

sensory region (crista ampullaris) contains what

Answer 17

Crista ampullaris contains sensory hair cells (fixed at the base, their cilia embededd in gelatious material – cupula)

Question 18

hair cells depolarize

Answer 18

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)

Question 19

otolith hair cells

Answer 19

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

Question 20

rest - what happens hair cells otolith organs

Answer 20

AP produced reg.

Question 21

move - what happens hair cells otolith organs

Answer 21

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

Question 22

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

Answer 22

hair cells move back to resting state

Question 23

hair cell bent toward or away kinocelia describe what happens

Answer 23

Stereocilia bent toward kinocilia – increase frequency of action potential

Stereocilia bent away from kinocelia - decrease frequency of action potentials