Pain & Temperature

Question 1

What are nociceptors?

Answer 1

Respond to noxious stimuli resulting from skin or soft tissue injury

Question 2

Nociceptor activation usually causes ____

Answer 2

Pain

Question 3

What is pain?

Answer 3

A subjective interpretation of unpleasant stimulus, not necessarily a product of nociceptor excitation

Question 4

Nociceptive pain

Answer 4

Pain resulting from nociceptor activation due to tissue injury and resultant inflammation

Question 5

neuropathic pain

Answer 5

Pain resulting from direct insult to the nerve

Question 6

Fast, sharp, pricking pain is transmitted to the spinal cord by ____ which carry…

Answer 6

Myelinated A-delta fibers
Thermal & mechanical noxious stimuli

Question 7

Slow dull pain is transmitted to the spinal cord by ____ which carry…

Answer 7

Unmyelinated C fibers
High intensity thermal, chemical, & mechanical noxious stimuli

Question 8

What might explain referred visceral pain?

Answer 8

Pain from viscera enters spinal cord the same way somatic pain does

Question 9

What is primary hyperalgesia?

Answer 9

Sensitization of surrounding nociceptors after injury or inflammation

Question 10

What stimulates primary hyperalgesia?

Answer 10

Release of bradykinin, prostaglandins, histamine, acetylcholine, substance P, CGRP, etc. from cells involved in injury

Question 11

How does the release of inflammatory products affect nociceptor activation?

Answer 11

Lowers activation threshold

Question 12

What is central hyperalgesia?

Answer 12

Sensitization of dorsal horn cells after injury due to persistent activation of NMDA receptors by glutamate releasing C fibers

Question 13

Changes/sensitization in dorsal horn may result in…

Answer 13

Long term decrease of pain threshold of patient

Question 14

Central axons of A-delta & C fibers pathway

Answer 14

• Ascend 2 segments in Dorsolateral fasciculus of Lissauer
• synapse in dorsal horn with nucleus proprius, Pericornual cells and Substantia gelatinosa

Question 15

Most synapses of primary A-delta and C fibers involve ____ that control pain perception

Answer 15

Interneurons

Question 16

Axons of nucleus proprius cross the midline and form the ____

Answer 16

Lateral spinothalamic tract

Question 17

Lateral spinothalamic tract ascends to the ____ in the ____

Answer 17

Thalamus
Anterolateral system

Question 18

Lateral spinothalamic tract sends collaterals to…

Answer 18

Reticular formation
Periaqueductal gray (emotional response)
Nucleus gracilis
Nucleus cuneatus
Hypothalamus (autonomic pain control)

Question 19

After spinothalamic fibers synapse in the thalamus, they ascend to the ____

Answer 19

Sensory cortex

Question 20

Explain Gate Control Theory of Pain

Answer 20

• A-beta mechanoreceptors send collaterals to Substantia gelatinosa —> inhibits nucleus proprius
• A-delta & C nociceptors send excitatory signals to nucleus proprius while inhibiting Substantia gelatinosa
• mechanoreceptors turn off pain, nociceptors turn on pain —> relative excitation of 2 pathways can modulate pain

Question 21

What is the Gate Control Theory of Pain?

Answer 21

Based on observation that proprioceptive & mechanical stimulation diminishes perception of pain

Question 22

Stimulation of periaqueductal gray results in…

Answer 22

• profound & specific analgesia (can feel touch & vibration, not pain)
• excitation of serotoninergic Raphe nuclei and noradrenergic locus caeruleus

Question 23

Raphe nuclei and locus caeruleus send fibers in the ____, resulting in…

Answer 23

Fasciculus of lissauer (DLF)
Inhibition of output of Pericornual cells & nucleus proprius

Question 24

Descending inhibitory pathways of periaqueductal gray ultimately interfere with…

Answer 24

Glutamate secretion of primary pain afferents

Question 25

Opioid administration in the periaqueductal gray results in ____

Answer 25

Anesthesia

Question 26

Enkephalins, beta-endorphins, and dynorphins are ____ released in various areas of the nervous system

Answer 26

Endogenous opioid peptides