NS VII Pain and Temperature Sensations Flashcards
when is body temperature the lowest
at 6 am
where are thermal receptors found
on free nerve endings in the skin, hypothalamus, spinal cord, and deep tissues
are cool or warm receptors more numerous
there are 3-10 times as many cool receptors
what are nociceptors activated by
extreme cold or heat
what fibers transmit warm and cool signals
C fibers and A Delta
what type of receptors are used in thermal sensation
TRP channels
what does temperature do to the rate of intracellular chemical reactions
increases it
what receptor does menthol activate and what temps
TRPM8 at cooler temperatures
what receptor does capsaicin activate and what temps
TRPV1 at warmer temps
how would you describe cold pain
tickling, pricking, aching, burning, numbing
how would you describe hot pain
sharp, pricking, stinging, burning, throbbing
what happens to cold/pain fibers if skin reaches freezing
they are no longer stimulated
what is the average skin temp
34-35 degrees C
at average skin temp are cool receptors or warm receptors activated more
equal
what happens at 45 degrees celcius of skin
heat/pain fibers are activated and sometimes cold fibers are activated too called paradoxical cold
do thermoreceptors adapt
almost but never completely
are thermoreceptors sensitive
very sensitive to changes in temperature
what happens to sensation when temperature reaches one of the pain thresholds
the sensation becomes more persistent throughout the stimulus
are nociceptors tonic or phasic
tonic
when are warm and cool receptors best able to detect a change
at the mid range of their temperature sensitivity
what happens to receptors as temperature increases
more receptors are activated and perception is increased
- increased rate of thermal receptors firing
the greater the area of skin affected by a thermal stimulus the greater______
the number of receptors, receptive fields, and first order neurons, and greater perceived sensation
is there are greater or lesser ability for detection of a temperature stimulus if a large region is activated
greaters
what receptor types are sensitive to chemicals
-vanilloid receptor subtype
- cold menthol receptor type 1 (CMR1/TRPM8)
what type of receptor is the vanilloid receptor and what is it activated by
-TRPV1
- activated by capsaicin, temperature greater than 43, and protons
what is the effect of the vanilloid receptor
decreases the threshold of channel activation so that heat is perceived at 33 C
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
what are the characteristics of thermoreceptors in the orofacial region
- small receptive fields
- more cool than warm receptors
do nociceptive thermal receptors have large or small receptive fields
large
are we able to detect warming or cooling more
warming
is the face or inner mucosa more sensitive to thermal change
the face
what location of thermoreceptors are most sensitive to changes in temperature
tongue
what can nociceptors be stimulated by
mechanical, thermal or chemical
what qualifies acute pain vs chronic pain
less than 6 months - acute pain
what are the two types of acute pain
-somatic and visceral
what is somatic pain from
skin, subcutaneous tissues or mucus membranes or muscles(superificial) , joints, tendons, or bones (deep)
describe superficial somatic pain and what fibers carry it
localized, sharp, pricking and burning
- A delta fibers
describe deep somatic pain and what fibers carry it
dull, aching, diffuse and can be referred
-C fibers
what is visceral pain from
a disease process or abnormal function involving an internal organ (visceral) or its covering (parietal)
describe true visceral pain and what fibers carry it
dull, diffuse, poorly localized and associated with nausea and autonomic symptons
- C fibers
describe parietal visceral pain and what fibers carry it
sharp, stabbing, and better localized than true pain
-A delta fibers
what types of visceral pain can be referred
both types
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
what are the three types of chronic pain
- nociceptive pain
-neuropathic pain
-mixed pain
what is nociceptive pain due to
activation of nociceptors
what is neuropathic pain due to
neuronal injury
describe the pain associated with neuropathic pain and what fibers carry it
-paroxysmal, sharp and stabbing
-a delta fibers
what is neuropathic pain associated with
hyperalgesia
what are the major difference in acute pain vs chronic pain
-acute pain has autonomic responses
-chronic pain has psychological component
what can moderate to severe pain do
increase morbidity and mortality
what chemicals excite nociceptors
substance P, ATP, calcitonin gene related peptide (CGRP), glutamate, aspartate
what chemicals sensitize nociceptors
substance P, prostaglandins, histamine, bradykinin
what chemicals inhibit nociceptors
enkephalins, beta endorphin, cannabinoids
what is allodynia
painful stimulus that should not cause pain
what does stimulation of nociceptors lead to
antidromal activation of nociceptive nerve terminals and release of substance P and CGRP
what is the triple response is neurogenic inflammation
-red flush around site o finjury
- local tissue edema
- sensitization to noxious stimuli
what is the NT of a delta fibers
glutamate
what stimulates a delta fibers
thermal and mechanical stimuli
what is the NT of c fibers
substance P
what stimulates C fibers
thermal, mechanical and chemical stimuli
what fibers are in the neospinothalamic tract and what info does it provide
-A delta fibers
-provides location, intensity, and duration information
what fibers are in the paleospinothalamic tract and where do these fibers synapse
- c fibers
- brainstem structures
what does the spinoreticular pathway do and what fibers
-mediates arousal and autonomic responses
- c fibers
what does the spinomesencephalic pathway do and what fibers
activates anti-nociceptive, descending pathways
what does the spinohypothalamic pathway do and what fibers
activates the hypothalamus
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
what types of neurons can second order neurons in the spinothalamic pathway be
nociceptive or wide dynamic range
what cranial nerves are in the dorsal horn
1 through 6
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
what cell type is most abundant in the dorsal horn
WDR neurons
what do WDR neurons do during repeated stimulation
increase their firing rate
which neurons have larger receptive fields: WDR or nocicpetive
WDR
where are nociceptive neurons found and what do they respond to
found in lamina I and respond to high threshold noxious stimulation
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
what are the mechanisms to inhibit pain
-gate control theory of pain
-pain inhibits pain
- conditioned pain modulation
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
what explains massage therapy and rubbing an area in pain to make it feel better
gate control theory of pain
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
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
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
what is analgesia
selective suppression of pain without effects on consciousness or other sensations
what is pain in the orofacial region conveyed into the CNS by
the trigeminospinothalamic tract and the trigeminoreticular tract
when would thermal stimuli cause sudden and stinging pain in teeth
with missing enamel and exposed dentin
what do weak air puffs to exposed dentin result in
intense pain
each afferent nerve innervates ___
multiple teeth
large receptive fields = _______
poor localization
what makes dentin sensitive
dentinal tubules
where are odontoblasts located
in the dentinal tubule and their cell body is on the surface of the dental pulp
is dentinal tubule radius more important or number
radius
describe tooth pulp
highly vascular, innervated but low compliance
describe dentin
mineralized avascular
what is dentin suprasensitive to
extreme temperatures and hyperosmotic solutions
what fibers carry dentinal and pulp nociceptors
a delta and C fibers (90%)
describe dentinal pain vs pulp pain and what fibers carry each
dentinal pain is sharp pain (a delta), pulp pain is dull (C fibers )
what are the theories for dental nociception
-neural theory
- hydrodynamic theory
-odontoblast transducer theory
what is the hydrodynamic theory
stimulus displaces fluid in dentinal tubules which activates mechanoreceptors in nerve endings of dentin r pulp
what is the neural theory
free nerve endings in dentinal tubules are activated
what is the odontoblast transducer theory
odontoblasts are excited and transduce the signal to nearby nerve cells
what are the receptors in the periodontal ligament
nociceptors and ruffini endings
what do ruffini endings in the periodontal ligament regulate
occlusion, mastication and biting
what portion of the periodontal ligament is most heavily innervated
apical portion
