L4

Question 1

grey matter composed of?

Answer 1

neuronal cell bodies and dendrites

Question 2

white matter?

Answer 2

tracts comprising axons

Question 3

2 sensory tracts

- what info do they carry

Answer 3

dorsal column: touch, pressure, kinesthesia

spinothalamic: nociceptive

Question 4

gracilis

cuneate

Answer 4

leg

arm

Question 5

4 motor tracts

Answer 5

lateral corticospinal tract
rubrospinal (red nucleus in midbrain)
reticulospinal (brainstem)
vestibulospinal (brainstem)

Question 6

mechanoreceptive info travelling to brain

Answer 6

travel ipsilateraly (dorsal column). decussate and dorsal column nuclei in thalamus. then to S1

Question 7

pain and temp info travels to brain

Answer 7

spinothalamic tract

- synapse and decussates on spinal cord. cross to anterolateral tract then up to thalamus

Question 8

nociceptvie and thermoreceptive afferents synapse where?

Answer 8

projection neurons in substantia gelatinosa of dorsal horn. cross to contralateral spinal cord, up a segment or two. join spinothalamic tract then up to thalamus & S1

Question 9

mid-thoracis, hemi-transsection of spinal cord consequences

Answer 9

motor - paralysis of leg on same side as cut.
sensory - ipsilateral, touch pressure. cut off for side thats cut. r pain and temp in tact. contralateral pain, temp gone, keep touch pressure

Question 10

pain and temp sensation in syringomyelia

Answer 10

• cyst grows in spinal cord, enlarges central cavity, destroys axons of projection neurons.
• pain temp abolished bilaterally in areas that cross over area which cavity extends

Question 11

pain sensation outlasts nociceptor activtiy

Answer 11

threshold to further pain/mechanical stimuli rediced in injured area. = mechanical hyperalgesia
secondary hyperalgesia = lew’s triple response.

Question 12

mechanism of hyperalgesia
primary - what mediators? purpose?
triple response:

Answer 12

K, bradykinin, prostaglandins : sensitize nociceptors
axo-axonic reflex - nociceptor firing release subP and CGRP = activate mast cell = release His, = vasocilation (inflammation)
vasodilation = bradykinin release (flare)
vasodilation results in edema (wheal)

Question 13

referred pain

Answer 13

sharing of projection neurons.
- cardiac pain felt in left arm/chest
liver, gall bladder & diaphragm felt in neck/shoulders.

Question 14

3 dimensions of pains

Answer 14

sensory-discriminative: intensity, location, duration.
affective-moticational: unpleasant, urge to escape
cognitive-evaluative: appraisal, distraction, cultural value (suppress, re-interpret)

Question 15

gate theory of pain

2 steps

Answer 15

1. transmission of pain sensation
2. analgesia (suppression)
   - inhibitory interneurons in substantia gelatinosa (dorsal horn) suppress nociceptive transmission in projection neurons
   - activated by large mechanoreceptor afferent, can cause inhibition of projection neurons

Question 16

molecular basis of pain transmission in spinal cord, dorsal horn

Answer 16

opiates decrease duration of AP, reduce excitatory transmitter release

• enkephalins & opiates: active K channels = hyperpolarize neuron = less responsive to pain
• naloxone: block opiate receptors.

Question 17

key analgesics

Answer 17

Aspirin, NSAIDS (inhibit prostaglandin syntehsis and release)
gabapentin - block c-fibers
opioids - block subs P release.

Question 18

endogenous analgesia

• descending endogenous analgesia
• electrical stimulation of PAG

Answer 18

• neurons descend from analgesic sysem in PAG, release opioid onto dendrites near projection neruon = suppress pain.
• descending endogenous alangeis = naloxone abolishes some forms of endogenous analgesia elicited by stress.
• E stim of PAG = reduce intractable pain of central origin