42 Skin senses - touch and temperature

Question 1

What are primary and secondary receptors? Give examples of each type of sensory receptors

Answer 1

1. Primary: specialized endings of afferent nerve
   - pain, mechanoreception, temperature, olfaction
2. Secondary: separate cells innervated by afferent nerve
   - taste, hearing (hair cells), vision

Question 2

Describe the flow of generation of receptor potential when sensory receptors detected stimuli.

Answer 2

• the increasing stimulus causes increasing receptor potential, which is graded depolarizing potentials
• the receptor potential is the result of opening and closing of ion channels (open > depolarize)
• big enough receptor potential can trigger an action potential

Question 3

In muscle spindles that are stretch receptors, when stretched, stretching of intrafusal muscle fiber causes membrane stretch, and thus opened the ion channels and cause depolarization. Most cell types work similar except?

Answer 3

Rods and cone cells, they hyperpolarize.

Question 4

What is adaptation?

Answer 4

decrease or absence of signal sending to the CNS despite presence of a sensory stimulus

Question 5

What is the modality and location in the skin of free nerve endings?

Answer 5

Modality: temperature and pain
Skin: hair skin

Question 6

What is the modality and location in the skin of Merkel discs?

Answer 6

Light touch;

Glabrous skin

Question 7

What is the modality and location in the skin of the Meissner corpuscle?

Answer 7

Touch;

Glabrous skin

Question 8

What is the modality and location in the skin of the Pacinian corpuscle?

Answer 8

Vibration, pressure;

Hairy skin

Question 9

What is the modality and location in the skin of the Ruffini’s ending?

Answer 9

Pressure;

glabrous skin

Question 10

Give examples of mechanoreceptors with small and large receptive fields.

Answer 10

Small: MM
- Meisner’s corpuscle, Merkel’s disk
Large: PR
- Pacinian corpuscle, Ruffini’s ending

Question 11

Give examples of mechanoreceptors with fast and slow adaptation.

Answer 11

Fast:
- Meissner’s corpuscle, Pacinian corpuscle
Slow:
- Merkel’s disk, Ruffini’s ending

Question 12

The primary somatosensory cortex is located at the ____________ gyrus of the cortex, which has a _________________ of the body which receives information from the ___________ side of the body.

Answer 12

Postcentral;
topographic map;
contralateral

Question 13

How is the location of sensation determined?

Answer 13

by where the signal will end in the map of the primary somatosensory cortex

Question 14

Cutaneous thermoreceptors are _______________________ that poses temperature sensitive ion channels in their membrane.

Answer 14

free nerve endings

Question 15

Give examples of the cutaneous thermoreceptors and their actions.

Answer 15

1. Warm receptors: narrow temperature range, begins to fire at 30 degrees Celcius
2. Cold receptors, broader range, steady firing at 20-30 degrees Celcius
3. Nociceptors - Transient Receptor Potential channels (TPR), extreme temperature (<15, >45), sensation of pain
4. Central thermoreceptors in the hypothalamus integrate signals from central and cutaneous thermoreceptors to generate final temperature perception