Pain Pathways (Exam II)

Question 1

Differentiate the sensory-discriminative & motivational-affective aspects of pain.

Answer 1

• Sensory-discriminative - Ascending pathways and the perception of pain (location, intensity, sensation, etc.)
• Motivational affective - responses to painful stimuli (Ex. arousal, reflexes, endocrine responses, and emotional changes)

Question 2

What is nociception?

Answer 2

• The experience of pain through a series of complex neurophysiologic processes.

Question 3

What are the four stages of pain perception?

Answer 3

1. Transduction (tissue level)
2. Transmission (via nerves)
3. Modulation (via spinal cord)
4. Perception (CNS)

Question 4

Where does the modulation of pain impulses occur?

Answer 4

• Dorsal horn of the spinal cord

Question 5

What drugs are used to affect the transduction of pain?
What specifically is being affected by these drugs?

Answer 5

• Local anesthetics & NSAIDs
• Peripheral nociceptors

Question 6

What acts as the central relay station for incoming pain signals?

Answer 6

Thalamus

Question 7

What drugs are used to affect the transmission of pain?
What specifically is being affected by these drugs?

Answer 7

• Local anesthetics
• Αδ and C fibers

Question 8

What drugs are used to affect the modulation of pain?
What specifically is being affected by these drugs?

Answer 8

• LA’s, opioids, ketamine, α2 agonists
• Afferent fibers of the dorsal horn

Question 9

What drugs are used to affect the perception of pain?
What specifically is being affected by these drugs?

Answer 9

• General anesthetics, opioids, α2 agonists
• Brain

Question 10

Where are nociceptors located?

Answer 10

• Skin
• Muscles
• Joints
• Viscera
• Vasculature

Question 11

What characterizes afferent C-fibers?

Answer 11

• Unmyelinated
• Pain from heat (burning) & sustained pressure
• Slow (less than 2 m/s)

Question 12

What characterizes Aδ fibers?

Answer 12

-Myelinated
- Type I: Aβ & Aδ (heat,mechanical, chemical)
- Type II: Aδ (heat)
- Fast (>2 m/s)

Question 13

What chemical mediators of pain are targeted with spinal anesthetics?

Answer 13

Peptides

• Substance P
• Calcitonin
• Bradykinin
• CGRP

Question 14

Which chemical mediator is released first in response to injury?

Answer 14

• Bradykinin

Question 15

What chemical mediators of pain are inhibited by NSAIDs?

Answer 15

Lipids
- Prostaglandins
- Thromboxanes

Question 16

What chemical mediators of pain are inhibited by cannabis?

Answer 16

Lipids
- Endocannabinoids

Question 17

What is sensitization?

Answer 17

• Decreased pain threshold (likely due to upregulation of receptors)

Question 18

Differentiate hyperalgesia and allodynia.

Answer 18

• Hyperalgesia - ↑ pain sensations to normally painful stimuli.
• Allodynia - perception of pain to things that aren’t normally painful.

Question 19

What characterizes primary hyperalgesia?

Answer 19

Hyperalgesia at original site of injury.

• Lower pain threshold
• Spontaneous pain
• Expansion of receptive field

Question 20

What characterizes secondary hyperalgesia?

Answer 20

• Sensitization of CNS → hyperalgesia from uninjured skin surrounding injury.

Question 21

What area of the brain accounts for the perception (location & intensity) of pain?

Answer 21

• Somatosensory Cortex I & II (SI & SII)

Question 22

What is the relay center for nociceptive and sensory activity?
How does sensory activity travel from this area to the cerebrum?

Answer 22

• Spinal Dorsal Horn
• Ascending pathways

Question 23

What areas of the brain may depress or facilitate the integration of painful information in the spinal dorsal horn?

Answer 23

• PAG - Peraqueductal Gray Matter
• RVM - Rostral Ventral Medulla

Question 24

Where are afferent C-fibers located in the spinal column?

Answer 24

• Dorsal horn: Lamina I & II

Question 25

What is another name for Lamina II? What drugs work here?

Answer 25

- Substantia gelatinosa - Opioids

Question 26

What nerve fibers are associated with an "open-gate" for pain? What nerve fibers can shut this gate?

Answer 26

- Aδ & C-fibers = **open** - Aβ fibers = **closed**

Question 27

What receptors does ketamine target for pain modulation?

Answer 27

- NMDA

Question 28

The excision of what structure would result in the complete loss of perception of pain?

Answer 28

Amygdala *Bonus points if you just said the whole brain you degenerate*.

Question 29

What neurotransmitters propagate excitatory transmissions in the spinal column?

Answer 29

- Glutamate - Calcitonin - Neuropeptide Y - Aspartate - Substance P

Question 30

What neurotransmitters propagate inhibitory transmissions in the spinal column?

Answer 30

- GABA_A - Glycine - Enkephalins - NE - Dopamine

Question 31

What are the four ascending pain pathways?

Answer 31

- Spinothalamic - Spinomedullary - Spinobulbar - Spinohypothalamic

Question 32

What information is carried by the spinothalamic pathway? What laminae are used?

Answer 32

- Pain, Temp, & Itch - Laminae I, VII, and VIII

Question 33

What information is carried by the spinobulbar pathway? What laminae are used?

Answer 33

- Behavior towards pain - Laminae I, V, and VII

Question 34

What information is carried by the spinohypothalamic pathway? What laminae are used?

Answer 34

- Autonomic, neuroendocrine & emotional aspects of pain - Laminae I, V, VII, & X.

Question 35

What part of the suprapinal pathway differentiates where pain is coming from?

Answer 35

S1 & S2 (Somatosensory cortex 1 & 2)

Question 36

What supraspinal areas deal with the emotional/motivational aspects of pain?

Answer 36

- Anterior cingulate cortex (ACC) - Insular Cortex (IC) - Amygdala

Question 37

Where do the descending inhibitory tracts originate? Where do they then synapse at?

Answer 37

- PAG (periaqeueductal gray matter) - Synapse at dorsal horn

Question 38

What neurotransmitters are increased with exercise?

Answer 38

- Endorphins - Enkephalins - Serotonin

Question 39

How do inhibitory tracts inhibit the propagation of painful stimuli?

Answer 39

**Hyperpolarizing Aδ & C fibers** - ↓ release of substance P - ↑ pK⁺ and inhibiting Ca⁺⁺ channels

Question 40

Where does the pain inhibiting impulse originate from in the descending inhibitory tracts?

Answer 40

PAG-RVM areas

Question 41

When is pain considered chronic rather than acute?

Answer 41

- If > 3 - 6 months - If pain persists beyond tissue healing

Question 42

Who is at increased risk of neuropathic chronic pain?

Answer 42

- Cancer patients - Diabetics

Question 43

What is the treatment for chronic neuropathic pain?

Answer 43

- Opioids - Gabapentin - Amitriptyline - Cannabis *All situation dependent*

Question 44

How is visceral pain characterized? What examples were given in lecture?

Answer 44

- Diffuse and poorly localized

Question 45

What is complex regional pain syndrome?

Answer 45

- Variety of painful issues following an injury (sponateous pain, hyperalgesia, edema, etc.)

Question 46

When can babies begin to perceive pain?

Answer 46

23 weeks

Question 47

How does pain affect the GI/GU system?

Answer 47

- ↑ SNS = ↑ sphincter tone and ↓ peristalsis = **N/V, ileus, distension**, etc. - Stress ulcers

Question 48

How can the effects of pain in the cardiovascular system be summarized?

Answer 48

↑ SNS *↑BP, HR, etc.*

Question 49

What hormones experience an increase in response to chronic pain?

Answer 49

**Catabolic Hormones** - Catecholamines - Cortisol - Glucagon

Question 50

What hormones experience a decrease in response to chronic pain?

Answer 50

**Anabolic Hormones** - Insulin - Testosterone

Question 51

What are the pulmonary effects of chronic pain?

Answer 51

- Shallow breathing → **atelectasis and pneumonia.**