NS VII Pain and Temperature Sensations Flashcards
1
Q
when is body temperature the lowest
A
at 6 am
2
Q
where are thermal receptors found
A
on free nerve endings in the skin, hypothalamus, spinal cord, and deep tissues
3
Q
are cool or warm receptors more numerous
A
there are 3-10 times as many cool receptors
4
Q
what are nociceptors activated by
A
extreme cold or heat
5
Q
what fibers transmit warm and cool signals
A
C fibers and A Delta
6
Q
what type of receptors are used in thermal sensation
A
TRP channels
7
Q
what does temperature do to the rate of intracellular chemical reactions
A
increases it
8
Q
what receptor does menthol activate and what temps
A
TRPM8 at cooler temperatures
9
Q
what receptor does capsaicin activate and what temps
A
TRPV1 at warmer temps
10
Q
how would you describe cold pain
A
tickling, pricking, aching, burning, numbing
11
Q
how would you describe hot pain
A
sharp, pricking, stinging, burning, throbbing
12
Q
what happens to cold/pain fibers if skin reaches freezing
A
they are no longer stimulated
13
Q
what is the average skin temp
A
34-35 degrees C
14
Q
at average skin temp are cool receptors or warm receptors activated more
A
equal
15
Q
what happens at 45 degrees celcius of skin
A
heat/pain fibers are activated and sometimes cold fibers are activated too called paradoxical cold
16
Q
do thermoreceptors adapt
A
almost but never completely
17
Q
are thermoreceptors sensitive
A
very sensitive to changes in temperature
18
Q
what happens to sensation when temperature reaches one of the pain thresholds
A
the sensation becomes more persistent throughout the stimulus
19
Q
are nociceptors tonic or phasic
A
tonic
20
Q
when are warm and cool receptors best able to detect a change
A
at the mid range of their temperature sensitivity
21
Q
what happens to receptors as temperature increases
A
more receptors are activated and perception is increased
- increased rate of thermal receptors firing
22
Q
the greater the area of skin affected by a thermal stimulus the greater______
A
the number of receptors, receptive fields, and first order neurons, and greater perceived sensation
23
Q
is there are greater or lesser ability for detection of a temperature stimulus if a large region is activated
A
greaters
24
Q
what receptor types are sensitive to chemicals
A
-vanilloid receptor subtype
- cold menthol receptor type 1 (CMR1/TRPM8)
25
what type of receptor is the vanilloid receptor and what is it activated by
-TRPV1
- activated by capsaicin, temperature greater than 43, and protons
26
what is the effect of the vanilloid receptor
decreases the threshold of channel activation so that heat is perceived at 33 C
27
what activates the Cold menthol receptor and what is the effect
-activated by menthol and related compounds
- effect: decreases the threshold of the channels so that warmer compounds are perceived as cold
28
what are the characteristics of thermoreceptors in the orofacial region
- small receptive fields
- more cool than warm receptors
29
do nociceptive thermal receptors have large or small receptive fields
large
30
are we able to detect warming or cooling more
warming
31
is the face or inner mucosa more sensitive to thermal change
the face
32
what location of thermoreceptors are most sensitive to changes in temperature
tongue
33
what can nociceptors be stimulated by
mechanical, thermal or chemical
34
what qualifies acute pain vs chronic pain
less than 6 months - acute pain
35
what are the two types of acute pain
-somatic and visceral
36
what is somatic pain from
skin, subcutaneous tissues or mucus membranes or muscles(superificial) , joints, tendons, or bones (deep)
37
describe superficial somatic pain and what fibers carry it
localized, sharp, pricking and burning
- A delta fibers
38
describe deep somatic pain and what fibers carry it
dull, aching, diffuse and can be referred
-C fibers
39
what is visceral pain from
a disease process or abnormal function involving an internal organ (visceral) or its covering (parietal)
40
describe true visceral pain and what fibers carry it
dull, diffuse, poorly localized and associated with nausea and autonomic symptons
- C fibers
41
describe parietal visceral pain and what fibers carry it
sharp, stabbing, and better localized than true pain
-A delta fibers
42
what types of visceral pain can be referred
both types
43
what is the pathway of referred pain
two nociceptive afferent neurons from different regions of the body converge on the same second order neuron. the brain doesnt know the true source of input and may make a mistake in interpretation
44
what are the three types of chronic pain
- nociceptive pain
-neuropathic pain
-mixed pain
45
what is nociceptive pain due to
activation of nociceptors
46
what is neuropathic pain due to
neuronal injury
47
describe the pain associated with neuropathic pain and what fibers carry it
-paroxysmal, sharp and stabbing
-a delta fibers
48
what is neuropathic pain associated with
hyperalgesia
49
what are the major difference in acute pain vs chronic pain
-acute pain has autonomic responses
-chronic pain has psychological component
50
what can moderate to severe pain do
increase morbidity and mortality
51
what chemicals excite nociceptors
substance P, ATP, calcitonin gene related peptide (CGRP), glutamate, aspartate
52
what chemicals sensitize nociceptors
substance P, prostaglandins, histamine, bradykinin
53
what chemicals inhibit nociceptors
enkephalins, beta endorphin, cannabinoids
54
what is allodynia
painful stimulus that should not cause pain
55
what does stimulation of nociceptors lead to
antidromal activation of nociceptive nerve terminals and release of substance P and CGRP
56
what is the triple response is neurogenic inflammation
-red flush around site o finjury
- local tissue edema
- sensitization to noxious stimuli
57
what is the NT of a delta fibers
glutamate
58
what stimulates a delta fibers
thermal and mechanical stimuli
59
what is the NT of c fibers
substance P
60
what stimulates C fibers
thermal, mechanical and chemical stimuli
61
what fibers are in the neospinothalamic tract and what info does it provide
-A delta fibers
-provides location, intensity, and duration information
62
what fibers are in the paleospinothalamic tract and where do these fibers synapse
- c fibers
- brainstem structures
63
what does the spinoreticular pathway do and what fibers
-mediates arousal and autonomic responses
- c fibers
64
what does the spinomesencephalic pathway do and what fibers
activates anti-nociceptive, descending pathways
65
what does the spinohypothalamic pathway do and what fibers
activates the hypothalamus
66
where are the first, second and third order neurons cell bodies located in the spinothalamic pathway
-first: dorsal root ganglion
-second: dorsal nuclei, axons dessucate via the anterior commisure and terminate in the thalamus
-third:thalamus, axons project to sensory cortex
67
what types of neurons can second order neurons in the spinothalamic pathway be
nociceptive or wide dynamic range
68
what cranial nerves are in the dorsal horn
1 through 6
69
what stimuli do nociceptive neurons receive vs WDR neurons
nociceptive neurons only receive noxious stimuli, WDR neurons receive input from non-noxious afferent fibers from a Beta, a delta, and c fibers
70
what cell type is most abundant in the dorsal horn
WDR neurons
71
what do WDR neurons do during repeated stimulation
increase their firing rate
72
which neurons have larger receptive fields: WDR or nocicpetive
WDR
73
where are nociceptive neurons found and what do they respond to
found in lamina I and respond to high threshold noxious stimulation
74
what are the three mechanisms for central modulation of pain to facilitate pain
-WDR neurons
- receptor field expansion
-some second order neurons increase their frequency of activation
75
what are the mechanisms to inhibit pain
-gate control theory of pain
-pain inhibits pain
- conditioned pain modulation
76
explain the gate control theory of pain
-activation of a beta fibers from the same region inhibits the spinothalamic pathway and reduces pain perception
-a beta fibers activate an inhibitory interneuron that causes post-synaptic inhibition of the second order neuron for the pain pathway. weaker signal is sent to thalamus
77
what explains massage therapy and rubbing an area in pain to make it feel better
gate control theory of pain
78
how does the pain inhibits pain theory work
-stimulate pain in other regions of the body to inhibit pain through GABA at second order WDR neurons in spinal cord
79
what is the mechanism being the conditioned pain modulation theory
a second noxious stimulus leads to activated of the PAG, NRM, and RVm in the brainstem which results in diffuse analgesic effect over the rest of the body
80
what do interneurons in the dorsal horn of the spinal cord release and what does it do
enkephalin which inhibits the first order and second order neurons
81
what is analgesia
selective suppression of pain without effects on consciousness or other sensations
82
what is pain in the orofacial region conveyed into the CNS by
the trigeminospinothalamic tract and the trigeminoreticular tract
83
when would thermal stimuli cause sudden and stinging pain in teeth
with missing enamel and exposed dentin
84
what do weak air puffs to exposed dentin result in
intense pain
85
each afferent nerve innervates ___
multiple teeth
86
large receptive fields = _______
poor localization
87
what makes dentin sensitive
dentinal tubules
88
where are odontoblasts located
in the dentinal tubule and their cell body is on the surface of the dental pulp
89
is dentinal tubule radius more important or number
radius
90
describe tooth pulp
highly vascular, innervated but low compliance
91
describe dentin
mineralized avascular
92
what is dentin suprasensitive to
extreme temperatures and hyperosmotic solutions
93
what fibers carry dentinal and pulp nociceptors
a delta and C fibers (90%)
94
describe dentinal pain vs pulp pain and what fibers carry each
dentinal pain is sharp pain (a delta), pulp pain is dull (C fibers )
95
what are the theories for dental nociception
-neural theory
- hydrodynamic theory
-odontoblast transducer theory
96
what is the hydrodynamic theory
stimulus displaces fluid in dentinal tubules which activates mechanoreceptors in nerve endings of dentin r pulp
97
what is the neural theory
free nerve endings in dentinal tubules are activated
98
what is the odontoblast transducer theory
odontoblasts are excited and transduce the signal to nearby nerve cells
99
what are the receptors in the periodontal ligament
nociceptors and ruffini endings
100
what do ruffini endings in the periodontal ligament regulate
occlusion, mastication and biting
101
what portion of the periodontal ligament is most heavily innervated
apical portion
