2 – Neuroanatomy of Pain Pathways

Question 1

Pain

Answer 1

• Arises in the BRAIN
• A CONSCIOUS experience (subjective experience of actual or impending harm)

Question 2

Phases of nociceptive pain

Answer 2

1. Transduction
2. Conduction
3. Transmission
4. Modulation
5. Perception

Question 3

Transduction

Answer 3

-proteins and VG ion channels convert thermal, mechanical or chemical energy into an AP

Question 4

Conduction

Answer 4

-AP moved through pain fibers to depolarize pre-synaptic terminal

Question 5

Transmission

Answer 5

-post-synaptic membrane activated, and signal is relayed in SC

Question 6

Modulation

Answer 6

-adaptive process with both excitatory and inhibitory mechanisms

Question 7

Perception

Answer 7

-integration of sensations, emotions and cognition that results in unique perception of pain

Question 8

Nociception

Answer 8

• Sensory (afferent) info that is relayed via ASCENDING pathways
• DETECTION of noxious stimuli by a subset of sensory neurons (nociceptors) to the CNS
  o A-delta and C fibers
• *can occur without pain

Question 9

Nociceptors

Answer 9

• A-delta and C fibers
• Smaller in size
• More numerous
• POLYmodal
• High threshold
• ubiquitous

Question 10

Nociceptors detect: and tissues that nociceptors supply

Answer 10

• Skin
• Muscle
• Bone
• Joints
• Viscera
• Head

Question 11

Nociceptors detect:

Answer 11

• Mechanical stimuli
• Thermal (heat or cold) stimuli
• Chemical (H+) stimuli
• *multiple ION CHANNEL RECEPTORS that are sensitive to all 3

Question 12

Action potential

Answer 12

• Voltage-gated Na+ channels = PROPAGATION
  o Blocked by local anesthetics

Question 13

What determines how much info about noxious stimuli is transmitted to the brain?

Answer 13

• State of excitability of the PAIN RELAY NEURON

Question 14

Brain regions involved in the experience of pain

Answer 14

• Cerebrum
• Diencephalon (thalamus)
• Brainstem (partially responsible for animals level of consciousness)
• Limbic system (memories and emotions)