nociception Flashcards
what is the difference between pain and nociception?
pain is psychological whereas nociception conveys information about tissue damage and stimuli
what are nociceptors?
peripheral nerve endings of primary sensory neurons whose cell bodies are located in the dorsal root and trigeminal ganglia
the perception of spicy food arises from?
nociceptors
do nociceptors fire as soon as you perceive pain?
no they start to fire once tissue damage starts
nociceptors DO or DON’T have peripheral structures that transduce and filter peripheral stimuli?
DON’T
_________ are the least differentiated of the sensory receptors in the skin
nociceptors
pain in humans is mediated by different classes of nociception ________ fibers
afferent fibers ( sensory)
describe thermal or mechanical nociceptors ( diameter, myelination, conduction speed, sensation)
they have small-diameter, thinly myelinated A∂ ( A delta ( they are slow compared to other myelinated axons) fibers that conduct at 5-30 m/s
activation of these fibers is associated with sensations of sharp pricking pain
describe polymodal nociceptors ( diameter, myelination, conduction speed, sensation)
small diameter, unmyelinated C fibers, conduct slowly .5-2 m/s, activated by a high intensity mechanical, chemical and hot or cold stimuli
how do noxious stimuli activate the nociceptor?
by depolarizing the membrane of the sensory ending
a tingling sensation is reported if the stimulus intensity is raised to a level that activates________ fibers in the peripheral nerve
A∂ fibers
If stimulation of A∂ fibers is intense enough then what sensation resutls?
a sharp pain
if stimulus is really highly intense what fibers are activated and what is the associated sensation?
C fibers ( which are very very slow) and a dull long lasting sensation of pain is experienced
when do you perceive dull throbbing pain?
after you injure something; since the C fibers which relay this sensation are so slow and long lasting due to lack of myelination
in which fibers is the TrpV1 receptor found?
both A∂ and C fibers
what stimui is TrpV1 receptor activated by?
capsaicin, heat, acids, and anandamine ( a cannaboid receptor stimulus)
Why is capsacin an agonist for TrpV1?
because it mimics endogenous ( i.e. things that are found in our bodies) vanilloids AKA endovailloids.
when are endovanilloids released?
with peripheral injury
what is hyperalgesia?
enhanced sensitivity and responsivity to stimulation of the area in and around ( e.g. flare region) the damaged tissue
release of what agents enhances responsiveness of nocioception endings?
bradykinin,histamine,prostaglandins, and others
electircal activity in the nociceptors stimulate local release of substances which cause ?
vasodialation, swelling, and release of histamine from mast cells
how do NSAIDs work?
by inhibiting cyclooxygenase which is important for biosynthesis of prostaglandins which make things leaky
are nociceptors needed in order to sense pain?
no, even w/o nociceptors pain can be sensed
injury of the peripheral nerve can result in loss of ________ input from the periphery to the spinal cord
( sensory) afferent input
in brachial plexus avulsion pts. do patients feel anything in the dermatomes of the affected area?
they feel a burning pain in the denervated area.
why do pts. feel a burning pain in the denervated area in a brachial plexus avulsion?
pain is though t to result from hyperactivity of the dorsal horn neurons in the deafferented ( sensory denervated) region of the cord.
where do nociceptor fibers cross?
at the level where they enter the spinal cord
where do nociceptive fibers terminate?
primarily in the superficial dorsal horn ( lamina I and II) some A∂ nociceptive fibers also project more deeply to lamina V
how do nociceptive cells enter the spinal cord?
nociceptive nerve cells enter the spinal cord via the dorsal roots.
nociceptive fibers ascend and descend in what tract?
the dorsolateral tract
what are wide dynamic range neurons? and where are they found?
neurons which receive input from mechanoreceptors and nociceptors.
they are found in lamina V of the dorsal horn
what are nociceptive specific fibers?
neurons that process pain information. They are excited solely by A∂ and C fibers and are found in lamina 1 of the dorsal horn.
what do wide dynamic range neurons respond to?
somatosensory and noxious stimuli.
do nociceptive specific neurons or Wide range dynamic neurons have a larger receptive field?
wide dynamic range neurons
what do the convergence of _____ and ______ nociceptors onto the same dorsal horn projection neuron cause _________?
what do the convergence of VISCERAL and CUTANEOUS nociceptors onto the same dorsal horn projection neuron cause REFERRED PAIN
Where is pain referred in angina ( inadequate perfusion of the heart)?
referred to upper chest wall and radiation to the arm, back, neck and head ( see pg 236 in purves)
where is esophageal pain referred?
the chest wall ( see pg 236 in purves)
where is ureteral pain referred?
lower back and abdomen
where is bladder pain referred?
the perineum
where is prostate pain referred?
above and below the effected side ( if characteristic distribution)
why does phantom limb occur?
because sensory information about the missing body part can still exist in the absence of peripheral input and therefore phantom pain can occur as well.
in what pathway does nocioceptive input from the upper body ( excluding the face ) and lower body travel?
the fibers cross the midline and ascend in to the brain stem and thalamus through the anterolateral spinothalmic pathway
in what pathway does nocioceptive info from the face travel?
axons from trigem , facial, and associated glossopharyngeal and vagus carry nociceptive info facial nociceptors and thermoreceptors to the brain stem, cross the midline and ascend into the trigeminothalamic tract
what is the major target of nuclei ascending pain and temperature axons ?
the ventral posterior nuclear (VPN) complex of the thalamus.
the ventral posterior medial nuclei receives nociception from the ___________?
face
the ventral posterior lateral nuclei receives nociception from__________?
all of the body except the face
are mechanossensory neurons in the same area of the thalamus as nociceptors? are they in the same system?
yes they are close by in the thalamus but they are NOT in the same system.
according to clinical studies does large areas of damage to the somatosensory cortex result in impaired response to noxious stimuli or loss of pain?
NO, large areas of damage to the somatosensory cortex DOESN’T result in impaired response to noxious stimuli or loss of pain
pathways for _________ and _________ projection neurons cross the midline to ascend the opposite side of the cord
pain and temperature
somatosensory pathway ascends _________ in the dorsal column of the cod and therefor a unilateral spinal lesion of this pathway would produce loss ?
somatosensory pathway ascends IPSILATERALLY n the dorsal column of the cod and therefor a unilateral spinal lesion of this pathway would produce loss TOUCH, PRESSURE, AND VIBRATION.
nociception in a lesion will be on the _______ side.
contralateral side ( sensation of pain )
dorsal column/medial lemniscal system is where ___________ fibers travel.
somatosensory ( AKA the epicritic somatosensory)
why does a zone of complete loss result at the area of the lesion?
because of the lisseur tracts going up and down so so some of the get both epictric and protopathic loss.
where is the site of termination of nociceptive afferent neurons and what else happen there?
they end at the laminae I, II, and V
and those neurons in the rostroventral medulla make inhibitory connections there
what doe neurons in the periaqueductal gray matter do in the rostroventral medulla do?
they make excitatory connection
this region of the rostroventral medulla includes the nucleus raphe magnus
endogenous peptide opioids don’t impact _____ ______ __________?
free nerve endings ( the peripheral system)
endogenous peptide opioids do impact _____ ______ __________?
a system in which the information coming in is damped.
endogenous opioids are found in the ___________?
rostroventral medulla ( in the dorsal horn)
the descending axons of the serotonergic and noradrenergic neurons from the nuclues raphe magnus contact the dendrites of the __________ ______ and the local __________________ in the superficial dorsal horn
the descending axons of the serotonergic and noradrenergic neurons from the nuclues raphe magnus contact the dendrites of the SPINOTHALAMIC TRACT and the local ENKEPHALIN -CONTAING INHIBITORY INTERNEURONS in the superficial dorsal horn.
descending inhibition of spinothalamic tract neurons appears to be mediated by the activation of _________ ___________ in the dorsal horn
enkephalin interneurons.
the superficial dorsal horn contains a high density of ____________ and ___________ containing interneurons close to the terminals of nociceptive afferent input.
enkephalin and dynorphin
where are opiate receptors located?
on terminals of nociceptive afferents and on dentrites of postsynaptic neurons
how do opiod peptides and opiates regulate nociceptive transmission?
in part by inhibiting release of glutamate, substance P, and other transmitters from the sensory neurons
transmitter release is supressed by the activation of?
opiate receptors in the sensory neurons
endogenous opiod peptides modulate nociceptive transmission at levels of the 1˚ afferent synapse by a combination of _______ and _________ actions.
presynaptic and post synaptic actions.
