Physiology of pain

Question 1

What are the different receptor types associated with the senses?

Answer 1

Mechanoreceptors
Chemoreceptors
Thermoreceptors
Nocireceptors
Proprioceptors

Question 2

What is the area called which receptors cover in their function?

Answer 2

Receptive field

Question 3

What determines the magnitude of response from a sensory stimuli?

Answer 3

The amplitude of depolarisation triggered

Question 4

Which factors determine the acuity of a sense over any given area?

Answer 4

Density of innervation

Size of receptive field

Question 5

Cutaneous sensation is transmitted through which 3 fibre types?

Answer 5

Aß
Aδ
C

Question 6

Describe Aß fibres.

Answer 6

Large
Myelinated
Responsible for, touch, vibration and pressure

Question 7

Describe Aδ fibres.

Answer 7

Small
Myelinated
Responsible for cold, “fast” pain and pressure

Question 8

Describe C fibres.

Answer 8

Unmyelinated

Responsible for warmth and “slow” pain

Question 9

Which receptor types mediate proprioception?

Answer 9

Aα
Aß

(In muscle spindle and GTO)

Question 10

Which receptor types mediate mechanoception?

Answer 10

Aα

Aß

Question 11

Which fibre types mediate nociception and thermoception?

Answer 11

Aδ

C

Question 12

Where is the ultimate termination of sensory information?

Answer 12

Somatosensory cortex (S1)

Question 13

What does constant stimulus do?

Answer 13

Decrease in sensitivity over time

Question 14

Describe lateral inhibition.

Answer 14

Activation of one sensory input causes synaptic inhibition of its neighbours
This cleans up sensory info

Question 15

What is convergence?

Answer 15

Saves on neurons

Reduces sensitivity

Question 16

What are some factors which may activate nocireceptor signal transduction?

Answer 16

Low pH
Heat
Local chemical mediators (histamine, prostaglandins)

Question 17

What is the mechanism of action of NSAIDs?

Answer 17

They inhibit cyclo-oxygenase which converts arachidonic acid to prostaglandins

Question 18

What is the mechanism of action of local anaesthetics?

Answer 18

Blocks Na+ action potentials and as a result, blocks all axonal transmission to the area

Question 19

What is transcutaneous nerve stimulation?

Answer 19

An electric current is produced by a device to stimulate the nerves for pain relief

Question 20

What is the mechanism of action of opiates?

Answer 20

Reduces sensitivity of nocireceptors

Blocks transmitter release at dorsal horn

Question 21

What is Gate Control Theory?

Answer 21

Non-painful sensations can override and reduce painful sensation when its input closes the nerve gates to painful input

Question 22

What is the function of the thalamus in pain sensation?

Answer 22

It is a secondary relay point
Receives input from the ascending pathway of the spinothalamic tract
Relays this info to the cingulate cortex and somatosensory cortex as well as the limbic system

Question 23

What is hyperalgesia?

Answer 23

Increased perception of pain

May even perceive non-noxious stimuli as noxious

Question 24

What is allodynia?

Answer 24

Decreased threshold for response

Question 25

What is neuropathic pain?

Answer 25

Pain which is caused by a primary lesion or dysfunction in the somatosensory nervous system