Sensory receptors Flashcards
All systems go through thalamus except
olfactory system
define receptor potential
detection of adequate stim by receptor proteins directly or indirectly to open ion channels to elicit depol in receptor neuron
define transduction channel
involves what?
process of detect STIMULUS AND transform info into voltage change (neural signal)
involves sensory receptor (direct gated channel) sensitive to phys stim (light, heat, cold, mech, chem)
describe receptor protein
example
what happens after change in membr potential
what stim interact iwth to elict change in membrane potential
ex = mechanoreceptor for physical movement
depol or hyperpol for ion gradient
describe voltage gated ion channel
usu second neuron in sensory cell
vesicle fusion to interact with ligand gated or GPCR receptor that require voltage to open
difference btwn voltage gated and transduction channel
transduction channel = NOT voltage dependent but depend on adequate stim
purpose of action potentials in long sensory receptors
where on cell does it exert effect
regenerative AP to carry info from receptor ending to synaptic release site
only affects limited part of cell with receptor ending
example of long sensory receptor
skin mechanoreceptor
cell body in DRG and axon travel along cord to sensory ending in skin
synapse with 2nd order neuron
mechanoreceptors
depol by ___
how does it do it?
depol by stretch
1) incr nonspecific cation in receptive area membrane
2) depol incr in graded fashion with intensity of stim
example of muscle mechanoreceptor activation
open with touch
muscle mechanoreceptors in sensory ending that DRG neurons extend into (spindle)
photoreceptors
hyperpol by ___
how?
hyperpol by light
when adequate stim arises, causes receptive area cation channel to close
example of rod photoreceptor
resting membrane potential and how it maintains
Vm rest = -40 due to high cation conductance
from high cGMP concentrations that open cGMP cation channels
example of rod photoreceptor
mechanism of activation
1) light enters –> rhodopsin binds I-cis-retinal –> transform into trans molec
2) activ G protein transductin
3) cGMP phosphodiesterase causes cGMP breakdown to guanosine
4) close cGMP cation channel (less cGMP) and hyperpol –> decr NT release
Labeled lines = how we perceive modality of stim
conscious appreciation of sensory modality determined by ___
determined by specific neuronal connections from sensory organs thru thalamus to cerebral cortex
convert physical energy to change in Vm to transmit info to 2nd order neuron
3 functions of sensory modality appreciation
1) conscious sensation
2) control movement
3) maintain arousal
route taken by sensory info that will become conscious
Light
Auditory
ALL THRU THALAMUS (except olfactory)
1) Light thru LGN of thalamus to visual cortex of occipital lobe
2) Auditory thru MGN to auditory cortex of temporal lobe
how is stim intensity encoded by sensory receptors
sensory info conveyed based on 4 attributes of a stim
1) modality
2) intensity
3) quality
4) location
attributes of stim
describe modality
how energy converted by nervous system (vision, eharing, smell, taste, touch, therm)
attributes of stim
describe intensity
perceived amount of sensation depending on stim strength
attributes of stim
describe quality
receptor cells convey info on certain stim properties (color of light or freq of stim by vibration)
attributes of stim
describe location
ability to locate site/source of stim and distinguish btwn 2 closely spaced stim
how do we encode stim intensity
as incr intensity of stim, incr magnitude of generator potential
also affects fraction of time transduction channels stay open for proprotion relation btwn stim and response
long sensory receptor cells code stim intensity as ___
incr in AP firing freq
A-alpha receptors = I
Nerve fibers
diameter
speed
muscle spindle afferent
tendon organ afferent
proprioception
myelinated
10-20um (largest = fastest)
60-120 msec
