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Anatomy Test 3 > Lect 5 Pain and Temperature > Flashcards

Lect 5 Pain and Temperature Flashcards

1
Q

temperature and pain receptors

A

thermoreceptors

nociceptors

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2
Q

nociceptors

A

respond to different stimuli

  • mechanical (crushing, cutting)
  • thermal (noxious cold or heat)
  • chemical (bradykinin, prostaglandin, histamine)
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3
Q

primaray afferent axons for pain and temp

A

A-delta and C-fibers

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4
Q

A-delta fibers

A

sharp localized pain
lightly myelinated
1st pain

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5
Q

C-fibers

A

dull and unlocalized pain, aching sensations
unmyelinated
2nd pain

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6
Q

Neuronal chain example 1st,2nd,3rd order

A

be able to draw this
1st order: periphery to dorsal horn of spinal cord; ipsilateral
2nd order: Spinal cord to thalamus; contralateral
3rd order: Thalamus to cerebral cortex

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7
Q

Anterolateral system

A

Pain and temp are carried here
Second order neurons travel within the anterior lateral aspect of the spinal cord and anterior lateral aspect of the brainstem tegmentum

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8
Q

Anterolateral system tracts

A

spino –> anterolateral system, all second order neurons originate in spinal cord
spinothalamic, spinoreticular, spinohypothalamic and spinomesencephalic

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9
Q

Spinothalamic tracts

A

axons of ALS that originate in the spinal cord and terminate in the thalamus
carries noxious & innocuous temp info, crude non-discriminative sensory info (not major touch pathway)
2 tracts
neospinothalamic tract
paleospinothalamic tract

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10
Q

Neospinothalamic tract

A

this neuronal chain carries sharo, localized pain info to primary somatosensory cortex
this cortical area allows for conscious awareness of the location and nature of the painful stimulus
cut from sharp object

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11
Q

Paleospinothalamic tract

A

neuronal chain carries dull, aching and poorly localized pain to secondary somatosensory cortex (S-II) and other cortical areas
-most fibers that carry this type of pain info take a multisynaptic course through the reticular formation before reaching the cerebral cortex

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12
Q

Lissauers Tract

A

ascends or descends 1-3 segments

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13
Q

substantia gelatinosa

A

aka lamina II
major site for pain and temperature
a delta fiber termination

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14
Q

1st order neuron of spinothalamic tract

A

generally A-delta fibers, C-fibers

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15
Q

lamina II

A

A delta fibers may synapse directly on lamina II interneurons or lamina I and V projection neurons, which have dendrites in lamina II

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16
Q

Laminae I and V

A

comprised of projection neurons. axons of these neurons form the neospinothalamic tract
can have dendrites and interneurons in lamina II

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17
Q

2nd order neurons of neospinothalamic tract

A

projection neurons in lamina I and V
have dendrites that extend into the substantia gelatinosa
communicated directly or thru interneurons with primary pain afferents

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18
Q

paleospinothalamic tract 2nd order neurons

A

laminae VI-VIII receive C fiber input via interneurons that project from lamina II
are projection neurons, their axons form the paleospinothalamic tract

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19
Q

White commissure of spinothalamic tract

A

where it crosses midline

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20
Q

Neospinothalamic tract 2nd order neuron synapse

A

synapses on Ventral posterior lateral Thalamic Nerve (VPL)

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21
Q

neospinothalamic 3rd order neuron synapse

A

synapses on primary somatosensory cortex (S-I)

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22
Q

Paleospinothalamic tract 2nd order neuron synapse

A

synapses on intralaminar thalamic nuclei (ILN)

10-40% of paleo fibers have been found to pass to the thalamus

23
Q

Paleospinothalamic tract 2nd order neuron synapse

A

S-II primary somatosensory cortex

anterior cingulate, insula

24
Q

Course of neo and paleospinothalamic tracts 3rd order

A

from VPL or ILN of thalamus -> 3rd order neurons project axons through posterior limb of the internal capsule to reach the cerebral cortex

25
Q

S-I location & function

A

primary somatosensory cortex, post central gyrus

cortical area allows for conscious awareness of location and nature of painful stimulus

26
Q

S-II location and function

A

paleo
somatosensory cortex, anterior cingulate cortex and insula
carries dull, aching and less well defined pain and sensation

majority of fibers take a multisynaptic course through the reticular formation

27
Q

Anterior cingulate

A

thought to mediate the suffering and emotional components of pain

28
Q

insula

A

contributes to emotional aspects of pain(c fibers)

29
Q

Overview of spinothalamic tract

A

Primary afferent (soma DRG) –> ascend/descend in lissauers tract –> Synapse in substantia gelatinos –> 2nd order neurons cross to contralateral ALS –> medulla –> pons –> midbrain –> Thalamus (VPL or ILN) –> cortext (S I, S II, anterior cingulate, insula)

30
Q

location of spinothalamic tract in medulla

A

ALS maintains similar position in the anterolateral tegmentum

31
Q

location of spinothalamic tract in pons

A

ALS maintains position in anterolateral tegmentum

32
Q

locaiton of spinothalamic tract in midbrain

A

ALS maintains position in anterolateral tegmentum

33
Q

Visceral afferent fibers

A

respond to excessive pressure, tension and inflammation in visceral organs
afferents enter the spinal cord and may by interpreted by the cerebral cortex as pain

34
Q

Why do we have pain in our left arm during a heart attack?

A

visceral afferents from the heart enter the upper thoracic spinal cord segments. In the spinal cord, these visceral pain afferents converge on the same spinothalamic tract cells reached by somatic pain fibers.
Brain interprets the activation of the spinothalamic tract fibers as pain in somatic region (chest and left arm)

35
Q

Where does the diaphragm refer pain?

A

shoulder

36
Q

Spinoreticular fibers

A

second order axons of LAS originated in spinal cord and terminate in the reticular formation
laminae VI thru VII/VIII receive c fiber input and give rise to spinoreticular fibers
**may be described as collateral branches of paleospinothalamic tract

37
Q

Spinoreticular fibers project to…

A

Thalamus
amygdala - involved in emotional response to pain
hypothalamus

38
Q

Synapse of spinoreticular fibers on thalamus

A

Intralaminar thalamic nuclei (ILN)

39
Q

ILN projects to..

A

widespread cortical areas including anterior cingulate cortex and insula
and frontal lobe (mediates heightened attention to painful stimuli)
-chronic pain often disrupts concentration

40
Q

spinohypothalamic tract

A

receives indirect input from reticular formation

receives bilateral pain information directly from the spinal cord

41
Q

hypothalamicspinal fibers

A

involved in regulation of autonomic outflow in response to painful stimuli

42
Q

hypothalamic spinal fiber projection

A

to the lateral horn of the spinal cord (location of preganglionic sympathetic neurons)

43
Q

Spinohypothalamic fiber projections

A

cross caudally and then move vertical ipsilaterally
Some cross contralaterally near hypothalamus at the supraoptic decussation
carry C pain and A delta pain

44
Q

spinomesencephalic tract

A

a delta fibers pass to lamina I and V, give rise to spinomesencephalic fibers, may be considered part of the neospinothalamic tract
pass through cerebral aqueduct
important in descending pain control pathway

45
Q

spinomesencephalic tract synapse

A

periaqueductal gray (PAG)

46
Q

periacqueductal gray

A

receives input from spinomesencephalic tract and hypothalamus, amygdala and several cortical areas

47
Q

Descending pain control pathway

A

believed to be reason why we do not feel pain in serious situation
general steps:
1. PAG receives input
2. Excitation of Enk interneurons
3. Inhibition of tonically active GABA interneurons
4. Excitation of serotonergic neurons
5. Release of serotonin in spinal cord

48
Q

PAG excitation

A

from the spinomesencephalic tract & other areas (amygdala, hypothalamus)

49
Q

Enk containing inhibitory neurons excitation

A

inhibits release of GABA from the tonically active GABAergic interneurons

50
Q

Inhibition of GABA neurons

A

disinhibit the PAG neurons that projecet to the raphe nucleus, this activates the descending pain control pathway

51
Q

Excitation of serotonergic neurons

A

in the raphe nucleus leads to release of serotonin from neurons at level of spinal cord

52
Q

serotonin in spinal cord

A

leads to inhibition of S-T tract neurons directly and indirectly by exciting inhibitory interneurons which in turn release enkephalin to inhibit S-T tract neurons

53
Q

opiates

A

opium, morphine control pain by activating opiate receptors in the PAG, initiate descending pathway

Anatomy Test 3 (9 decks)

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