Somatosensory Part 1.0 Flashcards
basics and mechanoreceptors
Somatosensory System: represented by 3 levels of integration associated w primary and association somatosensory cortices. What are they?
Somatic Sensation (somesthesis) - no perception, just awareness - consciousness of stimuli on somatic receptors
Somatic Perception
- generate attention - ego in it - “I notice this”
Somatic Representation
- third person - abstract knowledge, beliefs, attitudes about one’s own body
Intensity is…
more APs per unit time (higher frequency)
> increased stimulus intensity (the fire is about to burn you!), enhances the amplitude of the receptor potential - the harder you stimulate, the higher the receptor potential
The area of skin innervated by the branches of a single sensory receptor neuron is called?
a Cutaneous Receptive Field
Which RF’s are densely innervated and small in area? Peripheral or Proximal?
Peripheral (think feelers)
There are sensory receptor cells specialized in detecting stimuli of different qualities. The stimuli are categorized how?
Tactile Sensation
- touch
- pain
- temp
Proprioception
The axons of sensory neurons that are specialized in detecting stimuli of different qualities have membrane receptors that respond to specific stimuli. What are some physical differences between these cells/membrane receptors?
CT capsules, modified epithelial cells, hairs, OR directly (free nerve endings)
BUT, RECEPTORS ARE EITHER MODIFIED NON-NEURAL TISSUE CELLS OR AXONS THEMSELVES. (a stimulus will ultimately trigger an AP in the axon)
Which mechanoreceptors are associated with small RFs?
Meissner and Merkel (fingertips)
Which mechanoreceptors are associated with Large RFs?
Ruffini
- detects stretch only in certain directions
Pacinian
- located along median and ulnar nerves
Each sensory receptor cell has a set of protein receptors in its membrane which code for one modality more than another. What do we call this?
What are the sensory receptor proteins called?
“adequate stimulus” - the E that elicits the greatest response determines which neurons will be responsible for the perception of the sensory “modality”
Transient Receptor type ion channels, TRP
What are Compound APs?
recordings of the summed APs measured over time at a particular site on the nerve
Compound velocities depend on?
the degree of myelination. we all know myelinated axons are fatter and faster.
The further along the nerve you record, the more the compound APs separate by velocity so, close to the stimuli you will see what?
summed activity.
a big blast of activity - a lot of axons producing APs recorded simultaneously in the big peak!
(recorded further away you will see: a large peak then smaller peaks - clusters of axons with different velocities)
Nerve compound APs are classified by letters or numbers. What ones are the fastest?
Type 1 or A
slowest - type lV or C
Size and Density of Receptive fields helps the CNS to…
- locate stimulus
- distinguish size & shape of stimulus
- resolve spatial resolution
How does one maintain specificity regarding RFs?
RFs overlap - secondary RFs overlap and the spinal neurons that respond to diff secondary RFs can discern subtle differences among them.
Nerve compound action potentials are the peaks you see on the graph. The peaks correspond to?
the population size of axons w a specific degree of myelination and velocity
Discriminative Touch: What are the different mechanoreceptors embedded in CT or around hairs?
merkel, ruffini, meissner, pacinian, hair follicle
ea has a particular pattern of function, morphology, depth, RF, adaptation
Slow Adapting, SA, mechanoreceptors are?
Merkel and Ruffini
(A-beta)
[think MR. Slow, but remember, he’s mister Merkel]
Fast Adapting, FA, mechanoreceptors are?
Meissner, Pacinian, Hair follicle
A-beta
form, texture: fingers scanning a surface.
which mechanoreceptor?
where is it located?
Merkel Cells
(SA)
- located more superficial in basal layer of epidermis
skin stretch; perception of hand shape and position.
which mechanoreceptor?
what does it look like?
where is it located?
Ruffini Corpuscle (large thin spindle-shaped w layers of perineural tissue)
(SA)
- located deeper in dermis
skin movement and slip for grip control. movement across skin.
which mechanoreceptor?
what does it look like?
location?
Meissner Corpuscle (lamellar - schwann & CT)
(FA)
- located superficially under epidermis, but in dermis
Vibratory stimuli detected through hand held objects.
which mechanoreceptor?
what does it look like?
location?
Pacinian Corpuscle (onion-shaped lamellar - schwann & CT, encapsulates a single axon ending in dermis of glabrous skin)
(FA)
- located deeper in dermis (looks like onion)
Motion/direction of tactile stimuli. detect touch.
which mechanoreceptor?
what does it look like?
Hair follicle (axons surround base of hair - lanceolate)
(FA)
- located in dermis
