Ch. 7 Taste, Smell, Mechano (Book) Flashcards
chemoreceptors are specialized for info about the… and 2 types
chemical envir and transmitting it to neurons
gustatory (taste) receptors
olfactory receptors
airborne molecules first pass through a layer of _______ _______ before they reach olfactory receptors
aqueous solution
sensilla/sensillum
hollow hairlike projections with a pore that allows stimulant molecules to reach sensory cells
taste in a housefly
on its proboscis or feet each sensillum has dendrites from many receptor cells
each is sensitive to a different chemical stimulus
will chemical stimulation of just a single sensillum of a fly provoke a behavioral response?
yes, it will lower its proboscis to feed
where are taste receptors found in terrestrial vertebrates?
tongue
epiglottis
back of the mouth
pharynx/upper esophagus
taste receptors in vertebrates are grouped into _____ ___ surrounded by ____ ____
taste buds, basal cells
basal cells
surround taste buds and are progenitor cells that give rise to new taste receptors (they die in ~10 days)
5 taste qualities
sweet
salt
sout
bitter
umami (MSG)
evolution of taste qualities
sweet - rich in calories
salt - maintain water balance
sour/bitter - toxic/danger
salty mechanism
salty tastants like NaCl dissociates in water
Na enters receptors through a special Na channel that is always open in the apical memb (blocked by amiloride)
depolarizes cell
sour mechanism
H+ ions enter amiloride-sensitive Na channels of apical memb
Block K+ channels
depolarizes cell
sweet mechanism
alanine binds receptors that use a G protein to start a cascade that ends in the closing of K channels
bitter mechanism
quinine blocks K channels in apical memb
small resting Na current depolarizes the cell
bitter mechanism under study
quinine binding activates G protein gustducin
actives phospholipase C which increases IP3 to release Ca
do vertebrate taste receptors make APs?
yes, but don’t have axons
synapse onto neurons whose axons run into the facial, glossopharyngeal, and vagus nerves
labeled line coding
receptors connected to a specific set of axons
olfactory receptors in vertebrates
found in the nasal cavity (line turbinates)
arranged so a stream of air or water flows over them during ventilation
vomeronasal organ
olfactory chamber that mediates chemical communication btw animals of the same species
for pheremones
each receptor in the main olfactory epithelium has a long, thin _______ that terminates in a small ____ at the _____. what is found on the knobs
dendrite, knob, surface
thin cilia covered in the protein soln mucus
only _______ olfactory neruons respond to odors
ciliated
nasal olfactory transduction cascade
G protein activates adenylyl cyclase that increases intracellular cAMP
cAMP opens cation-selective channels –> depolarization
APs from olfactory receptor axons carry the signal where
olfactory bulb of the brain
glomeruli
spherical clusters of neurons
ex. olfactory bulbs of insects and invertebrates/vertebrates
what kind of stimulus activates mechanoreceptors
a stretch or distortion of plasma membrane
uses ion channels
sensory bristle
found of the surface of insects
a stiff hair associated with a single bipolar sensory neuron
endolymph
fluid with a high [K+] that bathes dendrites of sensory bristles
what happens when an insect sensory bristle is moved
the dendrite is deformed and stretch-actived cation-selective channels are opened
K+ flows in (unusual) instead of out, which depolarizes cell
hair cells of vertebrates
extremely sensitive mechanoreceptors
many cilia from the apical end of each cell
coupled by kinocilium to accessory structures
2 classes of hair cell cilia
kinocilium (single)
stereocilia 20-300 (non-motile)
kinocilium microtubule arrangement
9+2 like other motile cilia
stereocilia arrangement
increasing length from one side of the cell to another
mechanically linked and move as a bundle
ultimately, movement of the ________ produces an electrical signal (hair cells)
stereocilia
when the stereocilia bends toward the kinocilium, the hair cell ______ and when the stereocilia bends away from the kinocilium the hair cell ________
depolarizes, hyperpolarizes
lateral line system
fishes and amphibians
external receptors based on hair cells
detects movement in water
lateral line system receptors
kinocilia of many hair cells embedded in an accessory structure called a cupula
cupula bends toward kinocilia when displaced
at rest, about __% of channels in a hair cell are open, producing a resting potential of about -____
15%, -60mV
do hair cells produce APs?
no, they release nt in a graded fashion onto primary afferent neurons
asymmetry of hair cell output
displacement toward kinocilium produces larger depolarization than same displacement away from kinocilium (small hyperpolarization)
stratocyst
organ that detects an animal’s position and acceleration with respect to gravity
stratocyst structure
hollow fluid-filled cavity lined with mechanoreceptors that contact the stratolith
stratolith
structure made of sand grains, calcarous concentrations, or another dense material
must have a higher specific gravity than surrounding fluid
acquired from the animal’s surroundings or secreted by stratocyst epithelial cells
what happens to the startolith when an animal moves
it rests on different regions of the stratocyst epithelium, which stimulates tonic discharge from ciliated receptor cells
2 functions of the vertebrate ear
report position of the animal
hearing
in vertebrates, the organs of equilibrium reside in a membranous labyrinth with 2 chambers…
sacculus and utriculus surrounded by bone and filled with endolymph
utriculus
gives rise to 3 semicircular canals of the inner ear
hair cells here detect acceleration of the head, endolymph moves the cupula –> bends cilia of hair cells
all the hair cells in a semicircular canal have their kinocilia on the ____ side
same
so all are excited or inhibited at once
maculae
3 patches of hair cells below the semicircular canals
Detect tilt
what is sound
a mechanical vibration that propagates through air or water
travels as waves
the external ear functions as a ______
funnel that collects sound waves from the air and concentrates the pressure on the eardrum (tympanic membrane)
external structures of the ear… pinna and tragus
help collection of sound waves and modify directional sensitivity
to detect sound, airborne vibrations must be transmitted where
from the outer and middle ear to the fluid-filled inner ear where the auditory receptor hair cells are
auditory ossicles
malleus incus stapes
energy from moving eardrum is transmitted to the ossicles through the oval window to the inner ear
cochlea
fluid-filled chamber that looks like a snail shell containing the receptor hair cells
hair cells encode frequency and intensity of sound
perilymph
in the cochlea
high [Na+]
organ of corti
has cochlear hair cells and bathed in endolymph
inner hair cells of organ of corti vs outer hair cells
inner hair cells: detect vibrations
outer hair cells: touch tectorial memb and change length rapidly to amplify vibrations
cochlear electrical signals reflect _______ of receptor currents from numerous hair cells
summation
transduction happens with movement of basilar memb bends tips of stereocilia laterally
_______ K+ current depolarizes hair cells of ear
inward (unusual b/c of high K+ in endolymph)
tip links
fine strands that connect each stereocilium to its taller neighbor
when bent, all move and many ion channels are opened TRPA1 channels
electrical resonance frequency
the frequency a hair cell responds maximally to
Basilar membrane stuff
Diff freq activate diff regions
Stiff narrow end = high freq and amplitude
Wide floppy end = low freq and amplitude
