Touch and Pain

Question 1

2 types of skin

Answer 1

Glabrous (palms, feet), hairy (everywhere else)

Question 2

The typical process of the physiology of the skin sense response

Answer 2

stimulus contact > skin receptors fire > signal to brain via spinal cord > signal reaches somatosensensory cortex

Question 3

What are the 4 bodily senses

Answer 3

touch, pain, body sense, temperature

Question 4

Name the order of the tactile receptors in the epi/dermis

Answer 4

Merkel’s disc, meissner corpuscle , ruffini organ/Paccinian corpuscle (roughly in line under level of the hair follicle)

Question 5

Key role of Merkel’s disc

Answer 5

fine details

Question 6

Key role of Meissner corpuscle

Answer 6

flutter/light touch e.g. object falling through fingers

Question 7

Key role of ruffini organ

Answer 7

stretching (bigger movements)

Question 8

Key role of paccinian corpuscle

Answer 8

vibration, fine texture (e.g. using a tool like a pen or DIY)

Question 9

Which corpuscle has the largest receptive field (area of skin a cell received info about)

Answer 9

The paccinian corpuscles have a larger receptive field than the Meissner corpuscle

Question 10

What is 2-point discrimination

Answer 10

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

Question 11

Why was attempted communication via the back with blind people unsuccessful

Answer 11

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

Question 12

How does acuity change with experience (i.e. Braille readers)

Answer 12

They gain far more sensitivity in their hands, and certain areas of their somatosensory cortex has greater activity (similar in musicians)

Question 13

Advantages of active touch

Answer 13

More exploratory, more body contact with object, can search for more diagnostic parts of object + use body muscles to give more info about weight.

Question 14

Which cues can help with perceiving texture

Answer 14

Spatial cues (grooves/bumps), temporal cues (when moving finger across a surface)

Question 15

Paccinian corpuscle test

Answer 15

Fatiguing the receptor by overworking it (feel high frequency vibrations) = later be less good at perceiving texture via other receptors as PC is fatigued

Question 16

What is double dissociation

Answer 16

When you can only do one of either ‘WHAT’ processing or ‘WHERE’ processing

Question 17

What is tactile agnosia

Answer 17

Can’t identify object by touch but they can spatially (tell you the features)

Question 18

What is tactile extinction

Answer 18

aware of being touched on a contralesional limb, but seem unaware of similar contralesional touch if touched simultaneously on their ipsilesional limb

Question 19

Brain imaging in healthy participants- study involved feeling objects whilst in a scanner. What did they find?

Answer 19

WHAT the object was- primary/secondary somatosensory cortex lit up.
WHERE object was- superior parietal area lit up

Question 20

A top-down influence on touch (type of furry animal) ?. What brain area lit up?

Answer 20

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.

Question 21

Why can’t you tickle yourself?

Answer 21

1) Prior to an action we predict the consequences. But if we aren’t undertaking it feelings of expectation/surprise make a big difference

Question 22

How can you bypass the expectation of tickling yourself?

Answer 22

Via a metal arm, since there is some surprise as to how the new material will feel

Question 23

What are pain receptors called

Answer 23

Nociceptors

Question 24

What was the old view of pain

Answer 24

Overstimulation of any body system

Question 25

What are the 2 types of pain we can exprience and the associated fibres

Answer 25

A- delta fibres- fast pain (sharp) i.e. pinch, extreme temp

C fibres- slow pain (dull), lingers for longer (i.e spicy food, burn )

Question 26

Despite physical pain, what else can affect a pain experience

Answer 26

1) Mental state (i.e. battlefield analgesia)

2) occur in absence of stimulation (phantom limbs)

Question 27

Explain the gating of pain in the spinal cord

Answer 27

The gate control theory of pain asserts that non-painful input closes the “gates” to painful input, which prevents pain sensation from traveling to the central nervous system. Therefore, stimulation by non-noxious input is able to suppress pain.

Question 28

What can influence/reduce the gating of pain in the spinal cord

Answer 28

1) Non-painful tactile stimulation (massage, acupuncture)
2) Top-down input (expectation)
fixation on pain can make it worse, since more

Question 29

What is a phantom limb? Approx how many people who have an amputation experience it?

Answer 29

A patient will feel as though an amputated limb is still presently attached to their body.
Around 80% who have an amputation experience it

Question 30

What is proprioception

Answer 30

Sense of your body’s position (where it is in space)
i.e. which is why you often feel confused where your body is when you wake up in the morning, before you tense your muscles.
Due to proprioception, we don’t always need to look at our body parts to know where they are (i.e. if they are out of site, like under a table)
We can also use other systems to help with this e.g. vestibular system, tactile receptors

Question 31

What is kinesthesis

Answer 31

sense of body’s motion (movement of our limbs in space)

Question 32

Give some details about the man who ‘lost’ his body

Answer 32

He lost his sense of touch/kinesthesis/proprioception due to a viral infection.
In time he learnt to compensate for this through using visual information i.e. he has to think about moving each movement he wants to make (which muscles/nerves involved to make a movement succesfully)
- He lost a-alpha and A-beta pain receptors. Sensation of pain/temp to neck was helpful in his recovery.
-However when he is in darkness he immediately loses sense of movement, so must be in lit conditions at all times.

Question 33

Which new pain receptors was recently discovered

Answer 33

C-tactile fibres- the slow wave of touch that helps us distnguish why something feels nice