Pain

Question 1

Labeled Line Theory

and Descartes

Answer 1

Descartes (and others) believed pain was carried by specialized receptors (ie. We feel pain because pain receptors tell us that something is painful)

Question 2

which neurons have free nerve endings?

Answer 2

small diameter

Question 3

Nociceptor

Answer 3

Nociceptor is umbrella term for “noxious” receptor
Thermal, mechanical, chemo
Silent/sleeping nociceptors- don’t wake the sleeping giant
Polymodal nociceptors

Question 4

neurotransmitters of painful information

Answer 4

Glutamate
AMPA
NMDA
Substance P (neuropeptide)
Calcitonin gene related peptide (CGRP)

Question 5

pain of fibromyalgia

Answer 5

poorly localized

emotional

Question 6

Gate control theory of pain

Answer 6

Melzack and Wall

a computation in the substantia gelatinosa. If there is more non-noci than noci, it is viewed as not painful.

Lamina 1 and 2 is majority of aff end up. L3 and 4 talk back to 1 and 2 and can activate the SG and prevent signal from going up the spinal cord, but if 3 and 4 are not silencing it, pain will get transmitted.

Question 7

Specific properties of nociceptive and non-nociceptive signals together code for pain perception in the spinal cord

Answer 7

Some spinal cord layers contribute to pain-modulatory pathways by spino-bulbo-spinal mechanisms

Question 8

Spinoreticular and spinomesencephalic tracts

Answer 8

Type of information in pathway: Pain
Point of origin, receptors involved: Free nerve endings (TRP channels) in skin, viscera, muscles
Where primary cell bodies are located: DRG
Where 1st synapse is: Lamina I – II
Where in Spinal Cord it enters, travels: dorsal horn (Lissauer’s Fassciculus to ascend at least 1 segment), after 1st synapse, travels bilaterally, ascends through anterolateral spinothalamic tract
Where/if it decussates: Spinal cord, after 1st synapse
Where second synapse is: Medullary/Pontine reticular formation, parabrachial nucleus (spinoreticular); Periaquedcucatal Grey Matter (spinomesencephalic)
Final destination: Dorsal Horn of Spinal cord

Question 9

what neurons stop us feeling pain?

Answer 9

medulary raphe

Question 10

Major descending pathways form the PAG signal through the Raphe nuclei of the RVM to

Answer 10

either inhibit or excite the spinal cord nociceptive signals

Question 11

neurotransmitters of the PAG signal through the Raphe nuclei of the RVM to either inhibit or excite the spinal cord nociceptive signals

Answer 11

endorphins
enkephalins
norepinephrine
serotonin

Question 12

TENS

Answer 12

transcutaneous electrical nerve stimulation effectiveness supports the gate-control theory of pain

Question 13

hyperalgesia

Answer 13

NMDA does a fantastic job

Question 14

allodynia

Answer 14

non-nociceptors get taken as nociceptive signals

Question 15

windup

Answer 15

Repeated stimulation from the same source is interpreted as increasingly painful:

Question 16

axon reflex

Answer 16

contributes to windup.

damage to the fibers leads to increased signals in a pseudounipolar neuron because of retrograde action potentials.

Question 17

Is all pain the same?Some interesting differences:

Answer 17

Visceral pain info is ONLY carried by C-fibers (means it’s going to stick around for a long time and probably be associated with an emotional response)
Visceral pain does not “feel like” the damage/disruption responsible for the pain
Female predominance
Psychological intervention improves “well-being,” not necessarily painful symptoms