Exam 3 Week 13 ppt7 Pain modulation

Question 1

Two Principal theories of pain modulation and the two extra theories thrown in by Lake

Answer 1

1. Gate-control theory
2. Descending systems
   Extras:
   -Hormonal system
   -Endogenous cannabinoids

Question 2

Very basic initial mechanisms of the Gate-control theory

Answer 2

• involves the segmental Modulation at level of 1° afferent and relay cell.
• It begins by realizing that small caliber afferents C-fibers activate 2° neuron to signal pain

Question 3

two afferent fibers involved in Gate-control theory

Answer 3

A-beta and C fibers

Question 4

What is the role of the inhibitory interneuron?

Answer 4

• inhibitory interneuron block signal of pain by inhibiting the 2° neuron
• if it is inhibited then the pain signal can get through to the 2° neuron
• The inhibitory interneuron functions as the part of the gate control theory

Question 5

What do A-beta fibers do? (in general)

Answer 5

large myelinated afferent fibers that respond to touch, pressure, vibration

Question 6

How are A-beta fibers involved in gate theory?

Answer 6

by stimulating touch or pressure receptors in an area (of pain), Ab fiber activates an inhibitory interneuron to block signal of pain by inhibiting the 2° neuron

Question 7

How do small unmyelinated C fibers block override A-beta fibers

Answer 7

Very active C-fibers can use another inhibitory interneuron (black in this illustration) to block the inhibitory effect of the large caliber afferents

*So with moderate pain stimulation of tactile receptors can block the pain. Very severe pain can override this effect

Question 8

Where do the Descending systems start?

Answer 8

Cerebral cortex and hypothalamic projections to midbrain and brainstem (Periaqueductal gray, Locus coeruleus, and Raphe nuclei)

Question 9

What type of neurons descend from Periaqueductal gray?

Answer 9

Enkephalinergic neurons

Question 10

Where do Enkephalinergic neurons descend to?

Answer 10

Descend to both spinal cord and to control Raphe neurons

Question 11

What type of neurons descend from Locus coeruleus?

Answer 11

adrenergic neurons (Norepinephrine)

Question 12

Where do Noradrenergic neurons descend to?

Answer 12

Adrenergic neurons which descend to the spinal cored to release NE.
Both Noradrenergic and serotonergic pathways inhibit tract cells

Question 13

What type of neurons descend from Raphe nuclei?

Answer 13

serotonergic neurons

Question 14

Where do serotonergic neurons descend to?

Answer 14

descend to the spinal cord to release serotonin (5-HT)

Both Noradrenergic and serotonergic pathways inhibit tract cells

Question 15

3 bullet points from slides of what is occurring in dorsal horn in the descending system

Answer 15

1. Both Noradrenergic and serotonergic pathways inhibit tract cells (using primarily post-synaptic inhibition)
2. There are also GABA pre and post-synaptic inhibitory neurons
3. Enkephalinergic descending and spinal interneurons (both do pre-synaptic inhibition, but probably post-synaptic too)

Question 16

What is released in the hormone pain modulation system?

Answer 16

release of b-endorphin which is released as part of the pro-hormone proopiomelanocortin (POMC) which is release from the pituitary during stress and injury.

Question 17

What do the endorphins do?

Answer 17

act on spinal and other opioid receptors to block pain

Question 18

How does Endogenous cannabinoids work?

Answer 18

separates emotional component from discriminative component of pain

Question 19

Benefits of massage (2)

Answer 19

1. Increase local blood circulation to decrease local inflammatory agents
2. Activate low-threshold Ab fibers that inhibit nociceptive input to spinal cord

Question 20

Benefits of using heat (2)

Answer 20

1. increase local circulation to decrease local inflammatory agents
2. Counter-irritation and also activating low-threshold Ab fibers (Gate control mechanism)

Question 21

Benefits of using cold (2)

Answer 21

1. Decrease metabolism so decrease release of local inflammatory chemicals
2. Counter-irritation to blockage of nerves

Question 22

Two types of TENS highlighted by Lake

Answer 22

1. High-frequency, low intensity, electrodes over area of pain
2. Low-frequency, high-intensity, electrodes over acupuncture points

Question 23

How does High-frequency, low intensity TENS work?

Answer 23

has a counter irritation effect, activating low-threshold Ab fibers that inhibit nociceptive input to spinal cord – the Gate control mechanism

Question 24

How does Low-frequency, high-intensity TENS work?

Answer 24

electrodes over acupuncture points may elicit release of segmental and descending enkephalins and hormonal endorphins

Question 25

4 pharmacological approaches to treating pain and examples

Answer 25

1. Non-opioid analgesics – anti-inflammatory
Aspirin, acetaminephine, ibuprofen
2. Tricyclic antidepressants – norepinephrine and serotonin reuptake blocking
Imipramine, amitriptyline, doxepin
3. Anticonvulsants – Na+ blockers
Phenytoin, carbamazepine
4. Narcotic (opioid) analgesics
Morphine

Question 26

Acupuncture

Answer 26

• Long, fine needles are inserted into specific points along 12 cardinal meridians on the skin – named for the meridian and point along the meridian
• Produces anesthesia significant enough that in China, surgery is frequently performed with patient under acupuncture alone

Question 27

What pain modulating system does acupuncture use?

Answer 27

descending pain control systems

Question 28

Surgical approaches to treating pain (3)

Answer 28

1. Surgical cutting of the dorsal roots
2. Surgical lesioning of thalamus
3. Surgical implantation of stimulators to block pain

Question 29

what are three examples of tricyclic antidepressants used for pain?

Answer 29

tricyclic antidepressants – norepinephrine and serotonin reuptake blocking

1. Imipramine,
2. amitriptyline,
3. doxepin

Question 30

what are two examples of anticonvulsants used for pain?

Answer 30

Anticonvulsants – Na+ blockers

1. Phenytoin,
2. carbamazepine

Question 31

what is b-endorphin part of?

when is it released and from where?

Answer 31

proopiomelanocortin which is released from the the pituitary gland during stress and injury