Sensory Physiology Flashcards
Starting an AP
Sensory neurons have _______ that are opened or close in response to______
channels
stimulus
Starting an AP
for example, touch receptors have a _______ that is _____
Na channel
opened with deformation of the cell membrane
Starting an AP
Opening of channels produces a _________, similar to _____
local response
sub threshold response or epsp
Starting an AP
sub threshold response in sensory neurons is called
this depolarization is caused a “generator potential”
Starting an AP
getting an AP from stimulus
if the stimulus is strong enough or lasts long enough, the generator potentials will cause the afferent neuron to come to threshold and generate an AP
Starting an AP
where does the AP go
back to the spinal cord/brain
One of the best studied of the receptors that responds to touch
Pacinian Corpuscle
The Pacinian corpuscle is comprised of
alternating layers of membrane with fluid between them, surrounding the nerve ending
when we touch something, what happens to the pacinian corpuscle
all the layers of the membrane are deformed–> opening of mechanosensitive Na channels on the membrane and influx of Na–>generation of an AP back to the CNS
what happens when the stimulus is maintained on a pacinian corpuscle
the action potentials gradually die away as adaptation occurs
The adaptation in a pacinian corpuslce is due to
redistribution of fluid in the corpuscle so that the force is no longer transmitted to the nerve ending.
Much, but not all of the adaptation that occurs is the result of
changes in the periphery (directly altering the afferent)
In some cases of the receptor adaptation, the removal of the stimulus triggers
action potentials as the ending “reforms”
this is known as an afterdischarge
Afterdischarge is associated with
the persistence of the sensation after the stimulus eliciting the discharge has been removed (phantom glasses)
Sensory unit
the sensory nerve and all its branches
Receptive field
the area from which stimulation produces activation of the neuron
The number of ____ is one way of coding the intensity of a stimulus
Number of action potentials. (with greater intensity, we see more action potentials - with further increases we may se patterned discharges like doublets or triplets)
The number of ______ also increases with increased
receptors firing
The number of ______ also increases with increased
receptors firing
Just noticeable difference
the smallest difference that can be detected
a change of about 10% is usually required for conscious recognition of the change
The Relationship between perceived strength and actual (measured) intensity - Oricinaly described as
Weber Fechner Law
Perceived intensity =log(measured intensity)
The Relationship between perceived strength and actual (measured) intensity - New data suggests the following formula
perceived intensity =K(measured intensity)^A
where K and A are constants
The Relationship between perceived strength and actual (measured) intensity - K and A vary depending on
type of sensory receptor
K and A for muscle senses s
both are close to 1
meaning - our perceived intensity matches th actual intensity very closely
