Nociception

Question 1

The cell bodies of afferent neurons which contribute to the reflex arc are located in…

Answer 1

The dorsal root ganglion

Question 2

Majority of the nociceptors in the skin are this kind of receptor

Answer 2

Free nerve endings

Question 3

Which kinds of nerve fibres are involved in nociception (2)

Answer 3

A-delta and C

Question 4

Which kind of nerve fibres are involved in “fast” pain

Answer 4

A-delta

Question 5

Which kind of nerve fibres are involved in “slow” pain

Answer 5

C

Question 6

Describe the morphology of A-delta fibres

Answer 6

Myelinated

Question 7

Describe the morphology of C fibres

Answer 7

Unmyelinated, small diameter

Question 8

What are “silent” nociceptors, what kind of fibre are they made of?

Answer 8

Nociceptors which only develop sensitivity after injury (e.g. when u poke a bruise)

Question 9

What is the most innervated tissue in the body with respect to nociception?

Answer 9

The eye

Question 10

Within the eye, which is the most innervated tissue wrt nociception?

Answer 10

The cornea

Question 11

Describe the % makeup of the nociceptive fibers in the cornea

Answer 11

30% A-delta
70% C-type

Question 12

What is the life expectancy for someone who does not have a sense of pain?

Answer 12

Less than 25 years

Question 13

What are the 3 modes of nociception?

Answer 13

Thermal
Mechanical
Chemical

Question 14

What are the channels involved in chemical nociception?

Answer 14

ENaC

Question 15

What are the main channel associated with many modes of nociception, but primarily thermal nociception?

Answer 15

TRP

Question 16

What are the channels associated with mechanical nociception?

Answer 16

KNCK (stretch-sensitive K channels)
Piezo

Question 17

What is the channel associated with capsaicin nociception?

Answer 17

TRPV1

Question 18

Why does capsaicin on the skin lead to a burning sensation?

Answer 18

Because we have TRPV1 receptors in our skin

Question 19

The TRPV1 channel is activated by… (2)

Answer 19

Noxious heat (thermal)
Capsaicin (chemical)

Question 20

How can capsaicin be used as an analgesic?

Answer 20

Capsaicin induces long lasting desensitization of nociceptive fibers - could use this to our advantage to desensitize nerve fibers in arthritis, for example

Question 21

What is the channel activated by menthol?

Answer 21

TRPM8

Question 22

What is the cell which makes up majority of the epidermis?

Answer 22

Keratinocytes

Question 23

How are keratinocytes involved in nociception?

Answer 23

Under mechanical pressure, they will release ATP which can stimulate surrounding cells, including free nerve endings

Question 24

What is TRPV3?

Answer 24

Heat-sensitive TRP channel expressed in keratinocytes

Question 25

What chemical compound can activate TRPV3 channels?

Answer 25

Camphor (found in tiger balm)

Question 26

What sensation is experienced when TRPV3 is activated?

Answer 26

Warming

Question 27

When keratinocytes have knockout TRPV3, what happens to their camphor sensitivity?

Answer 27

Become insensitive to camphor

Question 28

Why is it significant scientifically that TRPV3 are not expressed in DRG?

Answer 28

Breaks down the idea that peripheral sensory detection is mediated solely by DRG, which was previously believed