Peripheral Pain

Question 1

What kind of neurons are nocicpetors?

Answer 1

pseudounipolar

Question 2

remak bundle

Answer 2

one schwann cell that can ensheath multiple axons, but myelinates only one axon segment

Question 3

What do the following connective tissue layers in a nerve surround:

• endoneurium
• perineurium
• epineurium

Answer 3

• endoneurium: surrounds axons
• perineurium: surrounds axon fascicles
• epineurium: surrounds entire nerve

Question 4

What kind of nerves are spinal ganglia associated with?

Answer 4

spinal and cranial nerves

Question 5

What kind of nerves are associated with autonomic ganglia?

Answer 5

sympathetic and parasympathetic nerves

Question 6

What kind of neurons do spinal ganglia contain? autonomic ganglia?

Answer 6

• spinal ganglia: large pseudounipolar sensory neurons
• autonomic ganglia: multipolar neurons

Question 7

Do synapses occur at spinal ganglia or autonomic ganglia?

Answer 7

autonomic ganglia

Question 8

Arrange the following from most to least myelinated:

• C
• Abeta
• Aalpha
• Adelta

Answer 8

Aalpha > Abeta > Adelta > C

Question 9

What are Aalpha fibers responsible for?

Answer 9

proprioceptors of skeletal muscle

Question 10

What are Abeta fibers responsible for?

Answer 10

mechanoreceptors in skin

Question 11

What are Adelta fibers responsible for?

Answer 11

sharp and immediate pain and temperature

Question 12

What are C fibers responsible for?

Answer 12

dull and achey temperature, pain, and itch

Question 13

Classify the Adelta and C nociceptors based on conduction velocity.

Answer 13

• Adelta: first, sharp pain
• C: second, prolonged and diffused pain; result from acute damage

Question 14

What do merkel receptors respond best to?

Answer 14

steady pressur from small objects

Question 15

What do Meissner corpuscles respond best to?

Answer 15

rubbing against skin

Question 16

What do Ruffini cylinders respond best to?

Answer 16

steady pressure and stretching of the skin (e.g. joint movement)

Question 17

What do Pacinian corpuscles respond best to?

Answer 17

changing stimulation

Question 18

What causes nociceptive pain? Examples?

Answer 18

• tissue damage
• burns, fractures, lacerations

Question 19

What causes inflammatory pain? Examples?

Answer 19

• inflammation initiated by autoimmune response
• gout, rheumatoid arthritis

Question 20

What causes neuropathic pain? Examples?

Answer 20

• nerve damage/somatosensory system
• diabetic neuropathy, carpal tunnel syndrome, complex regional pain syndrome

Question 21

What causes nociplastic pain?

Answer 21

• no clear evidence of tissue damage
• fibromyalgia, chronic lower back pain, IBS

Question 22

Which organ does not have nociceptors?

Answer 22

brain

Question 23

Can you still feel second pain if first pain is blocked?

Answer 23

yes

Question 24

What kind of channels are associated with nociceptors? What kind of stimulus activates these channels?

Answer 24

transient receptor potential (TRP) channels; activated by heat

Question 25

Where do C fiber afferents synapse with 2nd order neurons?

Answer 25

dorsal horn of spinal cord; rexed's laminae 1 and 2

Question 26

Where do Adelta fiber afferents synapse with 2nd order neurons?

Answer 26

dorsal horn of spinal cord; rexed's laminae 1 and 5

Question 27

What type of information is transmitted in the anterolateral (spinothalamic) pathway? Dorsal Column Medial Lemnisus pathway?

Answer 27

- anterolateral = pain and temperature - DCML = sensation, vibration, proprioception

Question 28

first order neuron path of the anterolateral path? DCML path?

Answer 28

- anterolaterl: nociceptor --> dorsal horn - DCML: receptor --> dorsal column --> medulla

Question 29

second order neuron path of the spinothalamic path? DCML path?

Answer 29

- spinothalamic: dorsal horn --> VPL nucleus of thalamus - DCML: medulla --> thalamus

Question 30

third order neuron path of the spinothalamic path? DCML path?

Answer 30

- spinothalamic: thalamus --> somatic sensory cortex - DCML: thalamus --> somatic sensory cortex

Question 31

Site of decussation in the spinothalamic path? DCML path?

Answer 31

- spinothalamic: cord - DCML: medulla

Question 32

In brown sequard syndrome, injury to the left hemi-cord causes?

Answer 32

- loss of pain/temperature on RIGHT side below lesion (spinothalamic) - loss of touch, vibration, proprioception on LEFT side below lesion (DCML)

Question 33

What system manages spinal pain suppression (i.e. peripheral)?

Answer 33

gate control hypothesis

Question 34

What systems manage supraspinal pain suppression (i.e. from the brain/CNS)?

Answer 34

- descending serotonergic and opioid inhibitory system - descending purinergic inhibitory system - descending adrenergic inhibitory system

Question 35

Describe the gate control hypothesis. What is the theory? Which order neuron does it act on?

Answer 35

theory: mechanoreceptors (pressure) blocks peripheral ascending pain; act on 2nd order neurons 1) Abeta fiber synapses on inhibitory interneuron 2) inhibitory interneuron synapses on C-fiber 3) decreased C fiber firing

Question 36

Describe descending control of central pain. Which order neuron does it act on?

Answer 36

act on 1st order neurons 1) PAG release enkephalin to Raphe nucleus 2) raphe nucelus release 5-HT to inhibit C fiber from releasing Sub-P 3) decreased C fiber firing in the dorsal horn

Question 37

What is chronic pain?

Answer 37

pain that persists past normal healing time (>3-6 months)

Question 38

hyperalgesia?

Answer 38

increased pain sensation to normally painful stimulus

Question 39

hyperesthesia?

Answer 39

increased sensitivity to stimulation (e.g. irritation)

Question 40

allodynia

Answer 40

perception of pain from non-noxious stimulus (e.g. tight clothes on sunburn)

Question 41

dysesthesia

Answer 41

unpleasant abnormal sensation (e.g. feel sick)

Question 42

Describe peripheral sensitization.

Answer 42

inflammatory substances sensitize/activate nociceptors

Question 43

Describe central sensitization.

Answer 43

transcription dependent and transcription independent