Special Senses - Auditory, Taste, Olfaction Flashcards
tympanic membrane
highly vascularized and innervated (vagus nerve)
-transmit sound waves –> mechanical waves
cerumen
antibacterial, lubrication, trap foreigns bodies
-otitis externa by washing out cerumen
amplification in oval window
vibrate ear drum –> signal through ossicles –> stimulate oval window
-amplification compensates for loss in the cochlea and overcomes resistance in perilymph
acoustic reflex
contract stapedius and tensor tympani to dampen the sound protecting the inner ear
2 types of hearing
- conductive (use ossicles)
- sensorineural (use cochlea)
do not need ossicle to hear during bone conduction
hearing loss disorders
- otitis media = middle ear infection
2. otosclerosis = ossification of ligaments; stapes cannot move against oval window
inner ear (cochlea)
- 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)
role of stria vascularis
pump K+ out of the cells into the endolymph –> high K+ levels
-maintain endolymph
signaling through organ of corti
wave –> vibrate Reissner membrane –> vibrate endolymph –> vibrate basilar (tectorial) membrane with hair cells embedded
basilar membrane vs. helicotrema
basilar
-requires high frequency to vibrate due to high tension (thicker)
-high pitched sounds
helicotrema (apex)
-needs lower frequency sounds to vibrate (thinner)
tonotopy
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)
cochlear amplifier
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
outer vs. inner hair cells
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
pathway for depolarization and NT release
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)
how is neural info. carried from inner hair cells
cochlear division of CN8
-bipolar neurons (type I spiral ganglion)
olfactory receptors
bipolar neurons surrounded by supporting cells and basal cells underneath
-sensitivity is variable with different stimuli
what nerve is found in olfactory epith. besides olfactory nerve?
trigeminal
-stimulated by irritants –> sneezing, lacrimation
how is smell conducted?
odorant binds to receptor –> activate GPCR –> + adenylyl cyclase and cAMP –> + nucleotide gated ion channel –> Na+ and Ca2+ entry for depolarization
3 ways for odor fatigue - adaptation
- receptor internalization after odorant binding
- Ca2+ inhibiting nuclear gated channel and adenylate cyclase
- synaptic inhibition by GABA
olfactory transduction
bypasses thalamus, and goes to orbitofrontal cortex (role in emotions, memory, flavor perception)
abnormalities of smell
- anosmia - complete absence
- hyposmia - diminished sensitivity - older age
- dysosmia - distorted
which papillae contain taste buds?
fungiform and circumvallate
receptors for taste
specific receptors for sweet, sour, umami, bitter
-do not integrate, but project to different areas of brain through vagus, facial, or glossopharyngeal nerve
e types of cells in taste bud
- sustenacular/supporting cell
- basal cell - stem cells
- gustatory - taste
bitter, sweet, and umami sensed by what?
G protein
-tastant binds to receptor –> + GPCR and G protein –> close K+ channels and release Ca2+ from ER
sour and salt sensed by what?
H+ ions and NaCl ions
- do not require receptors
- enter directly causing depolarization
gustatory pathway
taste buds –> CN 7,9,10 –> solitary nucleus (medulla) –> VPM of thalamus –> either gustatory cortex or hypothalamus/limbic system
what nerve also influences your taste?
trigeminal - associated with gustatory
-inner ions also influence appetite
abnormalities of taste
ageusia = absence of taste
dysgeusia = distorted taste
hypogeusia = diminished taste
gustatory hallucination = false sensation
