Peripheral Sensory Mechanisms Flashcards
(43 cards)
What does the somatosensory system do?
Mediate sensations from whole body surface, including skin and deeper tissues
Extrareceptor sense - tells us about outside world
What is the structure of the skin?
Most of body covered by hair skin
Palmar surface of hands and soles of feet covered by glabrous skin - skin ridges prominent
Why is the skin different on the hands and lips?
Specialised to obtain perceptual information from these body parts
How many mechanoreceptor types, in terms of sense of touch, are there in glabrous skin?
4
Which receptors are close to the surface?
Meissner corpuscles
Merkel complexes
Which receptors are deeper in the skin?
Ruffini organs
Pacinian corpuscles
What type of axons are these receptors innervated by?
Large myelinated axons
Cell bodies in dorsal root ganglia
Can you tell the receptor type by the axon?
No, all the axons look the same
Where are Meissner corpuscles?
Tips of dermal-epidermal folds
Where are Merkel cells?
In valleys of dermal-epidermal folds
Where are Ruffini corpuscles?
In upper dermis
Where are Pacinian corpuscles?
In deep dermis and hypodermis
What is the structure of touch receptor?
Cells of non-neural origin form capsules around nerve endings
Tethered into structure of skin
Each detects slightly different aspect of force
How is mechanical force detected by touch receptors?
Mechanical force applied
Radiates minute force through skin
Deforms receptors
What happens when the force gets too high; ie: is damaging?
Touch receptors don’t give any information - they’ve plateaued out
What happens to the ion channels in the touch receptors when a force is applied?
Membrane stretches
Na ion channels physically open
If Na depolarises membrane enough, action potential initiated
What determines receptor size?
Location of receptor
Why do deeper receptors have larger receptor fields?
Detect radiating forces over larger areas
Why do more superficial receptors have smaller receptor fields?
Detect forces over smaller areas
Define a slowly adapting receptor
Give off action potentials that are constant with stimulus applied
Have slight increase in receptor firing when stimulus first applied
Define a rapidly adapting receptor
Detects changes in stimulus only
Don’t signal if stimulus is continued to be applied, but doesn’t change over time
What are tactile responses related to?
A stimulus activating it
When do rapidly adapting receptors firer?
When stimulus is applied and then removed
How do nociceptors respond to a stimulus?
Increase in firing rate when stimulus is removed
