Pain and Temperature

Question 1

Stimulus for pain

Answer 1

1. Nociceptor stimulation
2. Temp. >45 and <5 C
3. Pressure, tension or compression of nerves
4. Chemicals released from injured tissue ex: bradykinin, prostaglandins, histamine

Question 2

Mesencephalic pain inhibitory system pathway

Answer 2

Periaqueductal grey matter (enkephalins),
Substantia niagra (dopamine) - 
Raphae nucleus (serotonin) - 
Internuncial neurons in spinal cord -
release of enkephalins - 
inhibit release of substance p

Question 3

1st order neuron in pain pathway

Answer 3

- in dorsal root ganglion
Fast pain:
- A delta
- relay to marginal nucleus in lamina 1
- release glutamate
Slow pain:
- C
- terminate in lamina 5
- release substance p

Question 4

2nd order neuron in pain pathway

Answer 4

Fast pain:
- from marginal nucleus
- cross to opp. side
- occupy lateral white column
- terminates in VPL nucleus of thalamus
- gives collaterals to reticular formation
Slow pain:
- from substantia gelatinosa
- cross to opp. side
- occupy lateral white column
- ends in reticular formation, PAG, tectum of midbrain

Question 5

3rd order neuron in pain pathway

Answer 5

Fast pain:
- from VPL
- reach post central gyrus areas 3, 1, 2
Slow pain:
- from thalamus, PAG, midbrain, reticular formation
- reach entire cerebral cortex, limbic system, hypothalamus

Question 6

Define referred pain

Answer 6

• Irritation of viscera may produce pain which is felt in a somatic structure that is present at a considerable distance from the viscera irritated.
• Dermatomal rule