Exam 3: Ch 7 Notes Flashcards
specialized sensory cells have different modalities
light
sound
heat
mechanical
chemical
the different modalities have specialized _______
channels
sensory neurons detect ______ and transduce it into ______ activity
stimuli, electrical activity
graded potentials
APs to CNS
invertebrate cell bodies are located in the ______
periphery
vertebrate cell bodies are located in the ______ _____
spinal cord
pathway to CNS from sensory cell
detecting cell –> localized release of nt –> stim neuron –> CNS
opsin
g-protein coupled receptor found in rods and cones
7 transmemb. domains
transduction
input to electrical activity
detect –> amplified 2nd messenger –> channels –> depol (AP) or hyperpol
there is wiring to specific dedicated _____ regions for each modality
brain
light, touch, heat, etc…
synesthesia
1 input generates more than 1 response
ex. see a color and get a taste
stretch receptors in muscles
stretch-activated channels
initial graded potential –> threshold –> AP
how are the neurons specialized in stretch activated receptors
neuron structure
gating of channel
stretch receptor in muscle in TTX
still get receptor potential so channels are not voltage-gated Na
if you increase the stimulus size you get…
larger graded receptor potential
higher frequency of AP
adaptation if tetanic stimulation
decrease in AP production
spike initiating zone shows no adaptation
ommatidium eye structure
6-8 photoreceptor cells + axons –> CNS
crystalline cone + lens pigment cells line large surface area
central rhabdome microvilli
2-3 degree visual field, reduced (pixelated) info
1 photon –>
amplification –>
detectible current (1nA)
2nd messenger
limulus –>
photons –> depol in eccentric cells
2 structures of a vertebrate eye
fovea
blind spot
fovea
center of field of view
highest activity (dense photoreceptors)
blind spot
where optic nerve is and blood vessels enter the eye
no photoreceptors
focus –>
lens shape –> sensitivity –> pupil
rods
black/white vision
more sensitive than cones
night vision
cones
color vision
less sensitive than rods (not good in low light)
1:1 ganglion cells
rhodopsin
structural membrane discs of rods and cones
large surface area
sensitivity –>
fovea –> “pit”
all other cell types pushed direct route to photoreceptors
vetrebrate eye depol
20mV
in dark there is constant inward Na current
when light shines, inward current reduced to -70mV (hyperpol)
dark current + rhodopsin
G-protein coupled receptor
cGMP gated channel
cis –> trans
trans –> activated protein enzyme activity –> cGMP levels –> cGMP gated channel –> change voltage
in the dark…
cGMP is produced and opens cGMP channels
Na goes in to depol -20mV
in the light…
rhodopsin 6 protein (transducin) –> phosphodiesterase (PDE) –> breaks down cGMP –> channels close –> less Na in so hyperpol to -70mV
dynamic range of vision
intensity and wave length
must have multiple receptor types w/ different tuning (rods/cones)
rods are ____ sensitive
intensity
red light doesn’t stimulate
cones are ______ sensitive
wavelength
depends on pigments
R/G colorblindness
x-linked recessive
rods must be stimulated by blue/green
pit vipers infrared vision
facial pits below eyes w/ sensory cells
transient receptor potential (TRP) - heat sensitive channels
heat –> open –> depol –> Ca2+
in vitro cultures kidney cells –>
Ca2+ dye –> heat up and see more Ca2+
neural control of electrical activity
uses chemical nt
sensitivity + range limits: ion channels, reversal potential, refractory period
how to increase range
combining receptors of multiple types (individual ranges)
photo/mechano receptors
touch-multiple types (2 superficial, 2 deep skin)
superficial mechanoreceptors
meisner’s – slowly adapting
merkel’s - rapidly adapting
deep mechanoreceptors
rufinni’s - slowly adapting
pacinian - rapidly adapting
pacinian
nerve ending wrapped in multiple layers and matrix
is rapid adaptation electrical or mechanical?
mostly mechanical properties of accessory structure
many layers of conn. tissue
spontaneous activity
levels are modified by input
increase sensitivity to small stimuli and to positive/negative versions of stim
crayfish tail
sensitivity maintained after constant stimulus
stretch whole abdomen, stretch isolated muscle, APs
stretch crayfish abdomen
in situ receptor –> APs
stretch crayfish isolated receptor
reduced APs
negative feedback
why does only strong activation drive activity in inhibitory neurons
maintain sensitivity in operating range
stop APs from maxing out frequency
hair cells are called
stereocilia
in our ears
lateral line system
amphibians/fish
detect how fast they’re swimming
how fast the water is moving
invertebrate stratocyst organ of balance
stratolith - rests on ciliated cells
semicircular canals
fluid filled
hair cells attached to canal wall
movement of head drags cupula through fluid
bends hair cells –> electrical activity
otolith organs
tilt (gravity based)
dense calcium carbonate crystals
pinna structure
amplifies specific frequencies and sounds from specific directions
pressure wave vibrations eardrum
malleus, incus, stapes lever system –> amplifies
size of tympanic membrane vs. oval window
middle ear: oval window
inner ear: fluid
hair cells on basilar membrane
are the same
region specific response
basilar membrane
frequency/intensity
different properties along length… width/stiffness
basilar membrane is stiffer where
at less wide end…. higher freq. max response
more flexible at wide end… low freq.
cochlea also known as
organ of corti
inner hair cells
transduction of vibration to electrical activity
outer hair cells
change length rapidly
tips touch tectorial membrane –> sensitivity –> amplify vibration in that region
how do hair cells generate electrical activity?
ions through specialized channels
mechanically (stretch) sensitive channels on the tips (tip links)
hairs diff lengths - hyperpol toward short, depol toward long
in hair cells at rest
channels are partially open
less tension at short, channels close –> hyperpol
more tension at tall, channels open more –> depol
changes in tip links
at short less Ca2+ in, less depol, less release –> nt release –> more release
flies have ______ _____ in proboscis and feet
taste bristles
salt channels for taste
Na channel constantly open
amiloride sensitive
sour channels for taste
H+ block K+ channels to depol
H+ go through Na+ channels to depol
some taste channels are _______ coupled
G-protein
sweet and bitter
sweet taste channels
alanine –> G-protein –> cAMP –> close K channel –> depol
bitter taste channels
diff G protein –> PLC-IP3
IP3 sensitive channel
drive release of Ca2+ from internal stores
olfaction channels
voltage gated and leak
high [kCl]out –> depol
optogenetics
light sensitive proteins –> channels
channel rhodopsins clone gene –> transfect neuron –> light sensitive –> activate neuron by flashing light on it
neuron specific promoters in optogenetics
promoter + channel rhodopsin
no metabolic side effects
target disease or memory
advantages of channel rhodopsin neuron specific promoters
precision of activation by illumination or cell-specific/region specific expression
speed of control (speed of light)
target specific pathways
