pain and temperature

Question 1

Thermoreceptors

Answer 1

respond to temp and temp changes

Question 2

Nociceptors

Answer 2

pain receptors, free nerve endings, respond to variety of stimuli such as: mechanical (crushing pressure, cutting) thermal (noxious heat or cold) chemical (bradykinin prostglandin histamine)

Question 3

Primary afferent axons for pain and temp?

Answer 3

A-delta fibers and C fibers. A delta are lightly myelinated/for sharp pain. C fibers are unmyelinated and for dull aching pain (2nd pain). Both also carry crude tactile sensations like stretching or squeezing and itch.

Question 4

Anterolateral system

Answer 4

carries pain and temperature and some crude sensation.

Question 5

Anterolateral 2nd order neurons

Answer 5

travel within anterior lateral aspect of spinal cord and anterior lateral aspect of brainstem tegmentum

Question 6

Tracts of Anterolateral system

Answer 6

spinothalamic, spinoreticular, spinohypothalamic, spinomesencephalic

Question 7

spinothalamic tract

Answer 7

Includes Neospinothalamic tract and peleospinothalamic tract. Carries noxious and innocuous temp info and crude/ non discriminative sensory info as well as pain

Question 8

neospinalthalamic tract

Answer 8

carries SHARP localized pain info to primary somato cortex,

Question 9

Paleospinothalamic Tract

Answer 9

carries dull aching and poorly localized pain info to secondary somatosensory cortex and other cotical areas, most fibers take multisynaptic course through reticular formation before reaching the cerebral cortex

Question 10

1st order neurons of spinothalamic tract

Answer 10

Generally A-delta fibers transmit sharp pain and C fibers carry dull pain, BOTH carry temp info.

Question 11

major synaptic site for pain and temperature in spinothalamic tract

Answer 11

Substantia Gelatinosa (lamina 2)

Question 12

Lissauer’s Tract

Answer 12

ascends or descends 1 to 3 segments

Question 13

Flow of pain info starting at a delta fibers

Answer 13

primarry afferent a delta fibers carry sharp pain to lamina 2, within lamina 2 a delta fibers synapse onto lamina 2 interneurons or lamina one or five projection neurons. Neurons in lamina 1 and 5 can also recieve pain signal from lamina 2 interneurons. Lamina one and 5 projection neurons form neospinothalamic tract (second order neurons)

Question 14

flow of info starting at C fibers

Answer 14

Primary afferent C fibers carry dull aching pain to lamina 2. Lamina 6-8 recieve it from interneurons from lamina 2. , Lamina 6-8 projection neurons form paleospinothalamic tract

Question 15

Describe how the neospinothalamic tract enters the brain

Answer 15

a delta fibers enter anterior white commissure and decussate, ascent to VPL nucleus of the thalaus, then third order neurons go to primary somatosensory cortex (location and nature of pain)

Question 16

Describe how paleospinothalamic tract enters brain

Answer 16

primary C fibers enter and synapse with 2ndary neurons and they go through anterior white commissure decussate and go to Intralaminar Thalamic Nuclei (10-40%), third order neurons go to S-2 anterior cingulate insula,

Question 17

Where do both neo and paleospinothalamic tracts project 3rd order neurons

Answer 17

3rd order neurons from either VPL or ILN go through posterior limb of internal capsule in order to reach cerebral cortex

Question 18

Where does the anterolateral pathway travel?

Answer 18

through the anterolateral aspect of the spinal cord and the anterolateral aspect of the brainstem tegmentum

Question 19

referred pain

Answer 19

Visceral afferent fibers respond to excessive pressure tension and inflammation in visceral organs, visceral afferents from heart enter upper thoracic spoinal cord segments then converge on same spinothalamic tract cells reached by pain fibers, so you will have pain in left side of the chest and left arm

Question 20

Spinoreticular tract

Answer 20

c fibers come in synapse on lamina 2 then go to lamina 6-8, this makes spinoreticular fiibers

Question 21

spinoreticular fibers

Answer 21

can be described as part of collateral branches of paleospinothalamic tract. They pass to reticular formation

Question 22

where does reticular formation project to

Answer 22

Thalamus ILN then to anterior cingulate cortex and insula (suffering/emotional response to pain) and frontal lobe. The amygdala and hypothalamus

Question 23

Spinohypothalamic tract fibers

Answer 23

axons from ALS originate in spinal cord and terminate in hypothalamus. Involved in autonomic outflow in response to pain. They can go straight up or decussate at the very end

Question 24

Spinomesencephalic tract fibers

Answer 24

axons of ALS that originate in spinal cord and terminate in mesencephalon (midbrain). It is important in descending system of pain modulation. It synapses on the periaqueductal Gray

Question 25

Which laminae give rise to spinomesencephalic tract?

Answer 25

1 and 5, they are collaterals of the neospinothalamic tract

Question 26

Periaqueductal gray

Answer 26

opiate receptors in abundance, can inhibit pain response