Lecture 21: Nociception

Question 1

Nociceptors traits

Answer 1

• Naked nerve endings
• Axons, A delta (medium to small, lightly myelinated) and C fibers (small and unmyelinated)
• Pain receptors are not fast

Question 2

Pain

Answer 2

Conscious perception of noxious stimuli

Noxious stimuli is good at activating reticular formation and telling the cortex to wake up

Question 3

Destinations for nociceptive information & what it does

Answer 3

• Local circuits > protective reflexes (in routine neuro exam)
• Cortex > conscious perception (where you decide how severe and where it is coming from)
• Reticular formation (series of nuclei in brainstem, stuff in middle of brainstem dont’ all have something to do with the other) > arousal and ANS responses
• Mesencephalon (rostral colliculi: visual grasp reflex)> orienting eyes/head and descending pain modulation
• Hypothalamus and limbic system (emotional responses) > ANS and emotional responses

Question 4

Nociceptive pathways for superficial pain

Answer 4

spinocervicothalamic Tract
* Primary destination is primary somostosensroy cortex of thalamus?
* Main conscious pathway, you associate this pathway with localized pain in big toe for instance.
* Mainly A delta fibers (in humans, sharp pricking pain)
* Good somatotopy (know the exact spot of stimulus)
* Arises primarily from the skin
* decussation at c1 and caudal medulla

Question 5

Nociceptive pathway for deep pain

Answer 5

• spinoreticular tract (robust to reticular formation,
• Target is the reticular formation (brainstem/limbic system), concerned with emotional responses to pain.
• Gonads are heavily connected here
• Consciousness reached indirectly, can have an appreciation
• Mainly C fibers (in humans, dull aching burning pain)
• Poor somatotopy
• Primarily from viscera and bone

ascending axons are present in lateral and ventral funiculi close to gre

Question 6

The hierarchy of functional loss in spinal cord disease is a function of what three things?

Answer 6

1. Size and myelination of fibers (big fat myelinated, more vulnerable. Teeny-tiny, mroe robust) The bigger they are, the harder they fall.
2. Location within the cord (deeper is more protected)
3. Diffuseness or discreteness of the tract (diffuse, spread out bilaterally, have to damage more of it to eliminate function)

Question 7

The hierarchy of functional loss in spinal cord disease is

Answer 7

1. proprioception
2. superficial pain
3. deep pain