Somatosensory and Pain - Kenyon Flashcards
(145 cards)
1
Q
What is the general function of primary afferent neurons?
A
Encode mechanical, chemical, or thermal stimulus into a receptor or generator potential
2
Q
Are generator and action potentials the same
A
NO
3
Q
Describe a generator potential?
A
small, graded, and NOT CONDUCTED.
4
Q
Generator potential is equivalent to what type of post-synaptic event?
A
EPSP
5
Q
Where are the cell bodies of PANs?
A
in the DRG
6
Q
Are there synapses in the DRG?
A
Normally speaking, NO
7
Q
Are there IPSPs or EPSPs in the DRG?
A
No, all electrical activity passes right through it
8
Q
“A” fibers have a (large/small) diameter and conduct (fast/slow)
A
large, fast
9
Q
C fibers are (large/small) diameter and conduct (fast/slow)
A
small, slow
10
Q
C and A-delta conduct what signals?
A
Pain and temperature
11
Q
which fiber type is the fastest and what type of signal does it carry?
A
A-beta; TVP
12
Q
what are the slowest fibers?
A
C and A-delta
13
Q
Does the fast/slow differentiation have any impact on actual ability to conduct?
A
NO
14
Q
Do specialized receptors of PAN’s adapt to stimuli?
A
Some adapt quickly, some slowly, some not at all. Theyre the goldilocks bears of neuroscience.
15
Q
In two-pt. discrimination, what happens as you move the points farther apart?
A
AP frequency from the central receptive field lowers while frequency increases in the lateral receptive fields
16
Q
Describe the pathway taken for TVP and Pain and Temp from the body and back of head?
A
PAN’s to DRG to dorsal roots to dorsal column to medial lemniscus
17
Q
Describe the path for TVP, pain, and temp, form the the face and teeth?
A
PAN’s to trigeminal ganglion
18
Q
When axons enter the spinal cord, what types of events utilize the pathway that synapse in Rexed Layer 3 of the cord?
A
spinal reflexes: knee jerk, somato-somatic, viscero-somatic
19
Q
When axons enter the spinal cord and branch without synapsing, what do these form?
A
The dorsal columns of he spinal cord
20
Q
Lower limbs form what tract?
A
medial gracile tract
21
Q
Upper limbs, trunk and neck form what tract?
A
lateral cuneate tract
22
Q
With respect to dorsal column somatotopy, what body structures will be more lateral? More medial?
A
lateral: occiput and neck
medial: lower limb and trunk
23
Q
Will we see facial innervation in the the somatotopy of the dorsal column?
A
No, that stuff goes through the trigeminal!
24
Q
What is the effect on TVP of lesions in the dorsal column? what does this tell us about TVP fibers?
A
There is PARTIAL loss of TVP; dorsal columns are NOT the only pathway for TVP
25
Axons from the dorsal columns synapse with second order neurons in which nuclei?
gracile nucleus
| cuneate nucleus
26
Is the information at the gracile and cuneate nuclei simply relayed or is it processed?
it is processed
27
The (blank) tract is the pathway in which axons go ventral and corss over to form the medial lemniscus
Internal Arcuate tract
28
Axons from the lower body end up (ventral/dorsal)
ventral
29
Fibers from the gracile or cuneate tracts synapse in the (blank or blank) nuclei
Gracile or cuneate nuclei
30
The gracile and cuneate nuclei are in which brain layer?
Caudal medulla
31
The internal arcuate tract connects the gracile and cuneate nuclei to the (blank)
medial lemniscus
32
Axons in the medial lemniscus synapse with third order neurons where?
Ventral Posterior Lateral nucleus of the thalamus
33
The VPL nucleus of the thalamus sends its fibers to what cortical structure and to which gyrus?
Post central gyrus of the primary sensory cortex
34
does the VP complex have all peripheral somatic sensory fibers?
yes!
35
Fibers from the trigeminal ganglion first enter at what brain level?
PONS
36
trigeminal fibers synapse at what nucleus in the Pons?
principal nucleus of trigeminal complex
37
Do fibers from the trigeminal travel on the medial or lateral lemniscus?
medial
38
Where does the crossing over ocurr in the trigeminal pathway?
After synapsing in the principal nucleus and meeting up with the medial lemniscus
39
Where does the crossing over occur in the somatosensory pathway?
In the caudal medulla, after synapsing in the gracile or cuneate nuclei and becoming the medal leminscus
40
Fibers in the trigeminal lemniscus synapse where in the brain proper?
VPM of the thalamus
41
Trigeminal fibers in the VPM travel to what cortical structure?
pimary somatic sensory cortex
42
With regard to the sensory cortex somatotopy, are structures of the face more medial or lateral?
lateral
43
what structures are most medial on cortical somatotopy?
Trunk, leg, feet, toes
44
the Ant. cerebral artery supplies what somatotopic structures?
tunk, leg, foot, and genitals
45
the middle cerebral artery suppplies what somatotopic structures?
arms, hands, face, tongue
46
Does the posterior cerebral artery supply any somatotopic structures?
noooooope
47
Is there anything coming out of the primary sensory cortex?
YES, DESCENDING branches going to the secondary sensory cortex
48
From the SII, to what brain structures do fibers go? What are their functions?
Limbic structures, amygdala, and hippocampus.
Involved in inhibitory pathways blocking out proprioception (not always aware of your shoes/socks), as well as tactile sensation and learning memory
49
Are there more ascending or descending axons?
Descending!
50
effective analgesic therapy increases the (blank) of life for pts with pain
quality
51
What three classes of drugs help with neuropathic pain?
1. COX 2 inhibitors
2. opioid analgesics
3. adjuvant analgesics
52
What fraction of pts actually get adequate neuropathic pain relief from current treatments?
1/3
53
When processing pain in the sensory-discriminative model, in what nucleus do pain fibers synapse?
Ventral posterior (VP) nucleus
54
After hitting the VP, where does pain go for the sensory-discriminatory model?
Somatosensory cortex (SI, SII)
55
In the affective-motivational model, what are the two cortical areas that are acivated?
Anterior cingulate cortex and insular cortex
56
From what nuclei do you travel to reach the ant. cingulate cortex and the insular cortex?
midline thalamic nucleus
57
lesions in what thalamic nuclei cause complete loss of contralateral pain and temp?
ventromedial nucleus
58
What are the two ways of measuring pain?
Self-reporting or fMRI
59
Nociceptors have their cell bodies where?
in the DRG
60
the goal of pain management is to manipulate, aka (blank), nociceptors to control the first stage of pain generation
KILLLLLL
61
Capsaicin receptors are part of the (blank) receptor family
TRPV1
62
(Pre/post)ganglionic sympathetic neurons will synapse in the (blank) following injury
post, DRG
63
Synapse of sympathetic fibers in the DRG will cause (blank)
pain
64
Nociceptors have a (higher/lower) threshold than thermoreceptors
higher!! First something feels good and warm before it burns!
65
Stimulation of (hi/low) threshold mechano/thermoreceptors is non painful
low
66
stimulation of high threshold (thermoreceptor/nociceptors) is painful
nociceptor
67
What is the order of conduction speed from fastest to slowest of c, A-delta, and TVP fibers?
TVP>A-delta>C
68
do A-delta fibers carry first or second pain?
first pain
69
T/F: C-fibers carry second pain
T
70
Besides pain, what two other stimuli do A-delta fibers carry?
mechano and mechanothermal
71
Can C-fibers carry several sorts of painful stimuli?
Yes, this is called polymodal
72
Is conduction rate the event that causes difference between first and second pain?
Nope
73
What is the general reason for difference in first and second pain?
Fibers are going to different areas of the brain
74
What three types of stimuli can excite nociceptors?
1. mechanical
2. thermal
3. chemical (pH)
75
what class of ion channels are involved in pain and temp info?
TRP channels
76
What three stimuli open capsaicin channels?
1. heat
2. low pH
3. capsaicin
77
T/F: the capsaicin channel is selective for Ca
F! It is NONSELECTIVE
78
T/F: capsaicin channels are regulated by intracellular Ca and enzymes
T
79
does capsaicin bind to the receptor outside of the plasma membrane or within the cytosol?
On the cytosolic side
80
Does the capsaicin receptor produce a generator potential or an AP?
generator potential
81
What ion that TRPV1 lets into the cell causes autoregulation of the channel?
Ca, of course
82
What receptor is involved in the itch response?
TRPA1
83
is TRPA1 metabotropic or ionotropic?
metabotropic
84
Binding different intracellular (blanks) will differentiate between pain and itch
GPCRs
85
Pain and temperature afferents synapse in the (blank)
dorsal horn
86
Axons from the secondary neurons cross and form the (blank) tract to the thalamus
anterolateral tract (spinothalamic)
87
lesion of the dorsal column will result in what specific defieciency beyond partial TVP loss?
loss of ability to detect direction and speed of stimulus
88
TVP and pain are (same/opposite) sides below the medulla
OPPOSITE
89
TVP and pain are on (same/opposite) sides above the medulla
SAME
90
TVP crosses over to the same as pain at what brain level?
caudal medulla
91
What tract does TVP travel on to reach the medial lemniscus to decussate?
the internal arcuate tract
92
At their entrances to the CNS, do both TVP and pain come up ipsilaterally?
NO; TVP ispalateral, pain contralateral
93
Pain travels through what spinal tract?
The spinalreticular tract within the anterolateral system
94
A lesion of one side of the spinal cord will result in reduced TVP on the (blank) side and reduced pain and temperature sensation on the (blank) side.
ispilateral, contralateral
95
When pain and temp come in from the face, what direction (up/down) do they first travel in the CNS?
Descend
96
Trigeminal pain and temp decussate onto the (blank) tract
trigeminothalamic tract
97
to what brain level does the trigeminal dive down to for pain and temp?
Enters at mid-pons, dives down to middle medulla
98
Between the mid pons and middle medulla pain and temp from BOTH sides of the face are on (blank) side(s) of the brainstem.
BOTH SIDES OF BRAINSTEM!
99
Sensory discriminative pathway mediates what three things?
1. location
2. intensity
3. quality of noxious stim
100
Affective-motivational pathway mediates what three sensations?
1. unpleasantness
2. anxiety
3. fear associated with pain
101
Sensory discriminative is in what part of the brain
somatosensory cortex
102
Affective-motivational pathway is associated with what parts of the brain? (6)
```
Amgydala
Hypothalamus
Periaqueductal grey
Reticular Formation
Cingulate Cortex
Insula
```
It's scary to sit down int the P-CHAIR (pain chair!)
103
Besides making you feel like absolute dog shit while you throw a pity-party for your pain, what actual useful thing can the affective-motivational pathway do?
it can dampen down those debby downer thoughts!
104
Projections to the reticular formation are in what brain structure?
Middle medulla
105
Affective-motivational pathway synapses at what nucleus and at what level?
Parabrachial nucleus in the mid pons
106
Fromt he affect-motivate path, Projections to these two structures come off at mid-pons
amygdala
| hypothalamus
107
What nucleus does the A-M pathway synapse in at the thalamus/
Intralaminar nuclei
108
What two terminal brain structures does the A-M pathway go to?
insula and cingulate cortex
109
Referred pain is (visceral/somatic) pain
visceral
110
T/F: A lesion of the dorsal column could alleviate cancer pain
T; cancer is visceral pain
111
What pathway does visceral/referred pain follow?
medial lemniscus, surprisingly
112
Where does referred pain synapse in the thalamus
VP nucleus
113
What terminal brain structure does referred pain go to? is this part of the A-M or S-D pathway?
insular cortex; A-M
114
What is hyperalgesia?
Increases sensitivity to a painful stimulus
115
What is allodynia?
Nonpainful simtuli now causes pain
116
Hyperalgesia and allodynia arise from both (blank and blank) mechanisms
peripheral and central
117
Sensitivity of nociceptors can be adjusted in the (blank)
periphery
118
An "inflammatory soup" of substances is released following (blank)
injury
119
What is result of releasing this inflammatory soup?
Sensitization of nociceptors
120
What chemicals are released during injury that sensitize the nociceptor?
```
ATP
prostaglandins
Histamine
Bradykynin
5-HT
H
Substance P
nerve growth factor
CGRP
```
121
Peripheral sensitization acts on a (positive/negative) feedback system
Positive
122
T/F: Nociceptive neurons themselves can release sensitizing compounds
T
123
COX inhibitors reduce pain by inhibiting sythesis of:
prostaglandins
124
What is windup?
progressive increase in response by a dorsal horn neuron due to repetitive stimulation
125
In central sensitization, cytokines promote transcription of (blank) that make prostaglandins that increase neuronal activity
COX-2
126
COX 2 inhibitors work on (blank) peripherally and (blank) centrally
DRG peripherally, spinal cord neurons centrally
127
damage to the pain pathways results in what kind of pain?
neuropathic
128
T/F: The perception and response to a painful stimulus is determined solely by the magnitude of the stimulus or activity in the primary afferent nociceptor.
F: IT IS NOT SOLEY DETERMINED
129
Descending pathways activate neurons in the (blank) of the midbrain
periaqueductual grey
130
A-M descending pathway is controlled at what 4 structures?
1. Amygdala
2. Hypothalamus
3. midbrain periaqueductal grey
4. Medullary reticular formation
131
What are the nuclei that the periquedecutal grey project to? (4)
1. parabrachial nucleus
2. dorsal raphe nucleus
3. locus coeruleus
4. medullary reticular formation
132
Where is the parabrachial nucleus?
junction of midbrain and pons
133
Where is the dorsal raphe nucleus?
Medulla
134
Where is the locus coeruleus/
PONS
135
Where is the medullary reticular formation?
medulla
136
In the (blank) horn of the spinal cord, activity in the descending pathways inhibits nociceptive activity
dorsal
137
What neurotransmitters are used for inhibition of pain?
Serotonin
| Enkephalins
138
Activation of GPCRs coupled with inactivation of Ca channels modulates pain how?
inhibits it
139
how does inactivation of Ca channels inhibit pain?
Inhibition of Ca influx prevents neurotransmitter release
140
What types of nuerons release enkephalins/
interneurons
141
Activation of low-threshold mechanoreceptors can also (blank) nociceptive activity.
inhibit
142
Where are the opioid receptors?
Periaqueductal grey and spinal cord
143
Is there a real neurochemical basis of the placebo effect?
YES
144
What drug blocks the placebo effect?
naloxone
145
Newborns exposed to repeated heel lances have increased
hyperalgesia and conditioning to painful stimuli
