Touch and Pain Flashcards
(33 cards)
2 types of skin
Glabrous (palms, feet), hairy (everywhere else)
The typical process of the physiology of the skin sense response
stimulus contact > skin receptors fire > signal to brain via spinal cord > signal reaches somatosensensory cortex
What are the 4 bodily senses
touch, pain, body sense, temperature
Name the order of the tactile receptors in the epi/dermis
Merkel’s disc, meissner corpuscle , ruffini organ/Paccinian corpuscle (roughly in line under level of the hair follicle)
Key role of Merkel’s disc
fine details
Key role of Meissner corpuscle
flutter/light touch e.g. object falling through fingers
Key role of ruffini organ
stretching (bigger movements)
Key role of paccinian corpuscle
vibration, fine texture (e.g. using a tool like a pen or DIY)
Which corpuscle has the largest receptive field (area of skin a cell received info about)
The paccinian corpuscles have a larger receptive field than the Meissner corpuscle
What is 2-point discrimination
smallest separation of 2 separate but adjacent points of stimulation to the skin (imagine the 2 points of a compass) where 2 distinct impressions can be felt
Why was attempted communication via the back with blind people unsuccessful
The back is far less sensitive than say compared to the hands, there are far fewer receptors.
(100 x more receptors per square cm on finger tip than on our back, essentially the ‘fovea’ of the skin)
Imagine the homonculus
How does acuity change with experience (i.e. Braille readers)
They gain far more sensitivity in their hands, and certain areas of their somatosensory cortex has greater activity (similar in musicians)
Advantages of active touch
More exploratory, more body contact with object, can search for more diagnostic parts of object + use body muscles to give more info about weight.
Which cues can help with perceiving texture
Spatial cues (grooves/bumps), temporal cues (when moving finger across a surface)
Paccinian corpuscle test
Fatiguing the receptor by overworking it (feel high frequency vibrations) = later be less good at perceiving texture via other receptors as PC is fatigued
What is double dissociation
When you can only do one of either ‘WHAT’ processing or ‘WHERE’ processing
What is tactile agnosia
Can’t identify object by touch but they can spatially (tell you the features)
What is tactile extinction
aware of being touched on a contralesional limb, but seem unaware of similar contralesional touch if touched simultaneously on their ipsilesional limb
Brain imaging in healthy participants- study involved feeling objects whilst in a scanner. What did they find?
WHAT the object was- primary/secondary somatosensory cortex lit up.
WHERE object was- superior parietal area lit up
A top-down influence on touch (type of furry animal) ?. What brain area lit up?
The cutaneous rabbit- 2 taps at wrist and elbow feels like one tap at 4 different points up to the elbow, kind of like a rabbit ‘jumping’ up your arm.
The area of somatosensory cortex corresponding to the middle of the arm saw activity, despite never being genuinely stimulated.
Why can’t you tickle yourself?
1) Prior to an action we predict the consequences. But if we aren’t undertaking it feelings of expectation/surprise make a big difference
How can you bypass the expectation of tickling yourself?
Via a metal arm, since there is some surprise as to how the new material will feel
What are pain receptors called
Nociceptors
What was the old view of pain
Overstimulation of any body system
