Nociception - Chapter 24

Question 1

Which fiber types transmit information relevant to pain? What sensation does each convey? What receptors do they contain? In which layers of the spine do they terminate?

Answer 1

A-delta (Thermal, noxious touch ie: mechanical; AMPA, NMDA,Transient Receptor Potential (TRP) channels, Layers 1,2,5), C (Delayed polymodal Pain, NK1 (neurokinin 1), Layers 1,2)

Question 2

What molecules are released at the site of injury?

Answer 2

Histamine, neurogrowth factor (NGF), Brain Derived Growth Factor (BDNF, released as a result of increased NGF)

Question 3

What function do endogenous opiates perform with relation to pain? Name three such neurotransmitters and their receptors:

Answer 3

Serve as a gating mechanism for the brain to regulate pain sensation.

• beta-endorphin -> mu receptor
• enkephalin -> delta receptor
• dynorphin -> kappa receptor

Question 4

How mechanism of action does enkephalin have to reduce pain sensitivity?

Answer 4

Post-synaptic inhibition: Opens k+ channels hyperpolarizing the target neuron
Pre-synaptic inhibition: reduces Ca2+ currents to reduce neurotransmitter release probability.

Question 5

Which fiber type is probably responsible for pain sensitization?

Answer 5

C fibers

Question 6

Define nociception:

Answer 6

the response to perceived or actual tissue damage

Question 7

Define the two types of persistent pain:

Answer 7

nociceptive: result from the direct activation of nociceptors in the skin or soft tissue in respone to tissue injury and usually arise from accompanying inflammation.
neuropathic: direct injury to nerves in the pns or cns