Special Senses - Auditory, Taste, Olfaction

Question 1

tympanic membrane

Answer 1

highly vascularized and innervated (vagus nerve)

-transmit sound waves –> mechanical waves

Question 2

cerumen

Answer 2

antibacterial, lubrication, trap foreigns bodies

-otitis externa by washing out cerumen

Question 3

amplification in oval window

Answer 3

vibrate ear drum –> signal through ossicles –> stimulate oval window
-amplification compensates for loss in the cochlea and overcomes resistance in perilymph

Question 4

acoustic reflex

Answer 4

contract stapedius and tensor tympani to dampen the sound protecting the inner ear

Question 5

2 types of hearing

Answer 5

1. conductive (use ossicles)
2. sensorineural (use cochlea)

do not need ossicle to hear during bone conduction

Question 6

hearing loss disorders

Answer 6

1. otitis media = middle ear infection

2. otosclerosis = ossification of ligaments; stapes cannot move against oval window

Question 7

inner ear (cochlea)

Answer 7

• scala vestibuli (above) and scala tympani (below) - contain perilymph (high Na+, low K+)
• scala media - contain endolymph (high K+ and Ca2+)
• vestibuli (starts with oval window)
• tympani (ends with round window)

Question 8

role of stria vascularis

Answer 8

pump K+ out of the cells into the endolymph –> high K+ levels
-maintain endolymph

Question 9

signaling through organ of corti

Answer 9

wave –> vibrate Reissner membrane –> vibrate endolymph –> vibrate basilar (tectorial) membrane with hair cells embedded

Question 10

basilar membrane vs. helicotrema

Answer 10

basilar
-requires high frequency to vibrate due to high tension (thicker)
-high pitched sounds
helicotrema (apex)
-needs lower frequency sounds to vibrate (thinner)

Question 11

tonotopy

Answer 11

tone discrimination

• map areas of basilar membrane frequencies along cochlear duct –> differentiate b/w high and low pitch tones
• cochlear amplifier help distinguish b/w resolution
• lose energy as you move down cochlea –> low amplitude voices never reach end (heard best at base)

Question 12

cochlear amplifier

Answer 12

increase vibration and improve resolution

• amplify signal by outer hair cells contraction of prestin protein (depolarized by K+ from stria vascularis)
• transmit wave to inner hair cells amplifying wave

Question 13

outer vs. inner hair cells

Answer 13

outer - amplify signal

• prestin protein - deficiency –> deafness or loss of hearing
• destroyed by ototoxic drugs –> lose amplification
• get efferent inputs

inner hair cells - involved in hearing, in tectorial membrane

• synapse with auditory/acoustic nerve (CN8) –> release glutamate
• afferent signals

Question 14

pathway for depolarization and NT release

Answer 14

basilar membrane vibrates tectorial membrane –> bend steriocilia –> pull on tip link opening ion gates –> K+ from stria vascularis enters causing depolarization –> Ca2+ entry and NT release (glutamate)

Question 15

how is neural info. carried from inner hair cells

Answer 15

cochlear division of CN8

-bipolar neurons (type I spiral ganglion)

Question 16

olfactory receptors

Answer 16

bipolar neurons surrounded by supporting cells and basal cells underneath
-sensitivity is variable with different stimuli

Question 17

what nerve is found in olfactory epith. besides olfactory nerve?

Answer 17

trigeminal

-stimulated by irritants –> sneezing, lacrimation

Question 18

how is smell conducted?

Answer 18

odorant binds to receptor –> activate GPCR –> + adenylyl cyclase and cAMP –> + nucleotide gated ion channel –> Na+ and Ca2+ entry for depolarization

Question 19

3 ways for odor fatigue - adaptation

Answer 19

1. receptor internalization after odorant binding
2. Ca2+ inhibiting nuclear gated channel and adenylate cyclase
3. synaptic inhibition by GABA

Question 20

olfactory transduction

Answer 20

bypasses thalamus, and goes to orbitofrontal cortex (role in emotions, memory, flavor perception)

Question 21

abnormalities of smell

Answer 21

1. anosmia - complete absence
2. hyposmia - diminished sensitivity - older age
3. dysosmia - distorted

Question 22

which papillae contain taste buds?

Answer 22

fungiform and circumvallate

Question 23

receptors for taste

Answer 23

specific receptors for sweet, sour, umami, bitter

-do not integrate, but project to different areas of brain through vagus, facial, or glossopharyngeal nerve

Question 24

e types of cells in taste bud

Answer 24

1. sustenacular/supporting cell
2. basal cell - stem cells
3. gustatory - taste

Question 25

bitter, sweet, and umami sensed by what?

Answer 25

G protein

-tastant binds to receptor –> + GPCR and G protein –> close K+ channels and release Ca2+ from ER

Question 26

sour and salt sensed by what?

Answer 26

H+ ions and NaCl ions

• do not require receptors
• enter directly causing depolarization

Question 27

gustatory pathway

Answer 27

taste buds –> CN 7,9,10 –> solitary nucleus (medulla) –> VPM of thalamus –> either gustatory cortex or hypothalamus/limbic system

Question 28

what nerve also influences your taste?

Answer 28

trigeminal - associated with gustatory

-inner ions also influence appetite

Question 29

abnormalities of taste

Answer 29

ageusia = absence of taste
dysgeusia = distorted taste
hypogeusia = diminished taste
gustatory hallucination = false sensation