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Stack #215245

Neuro Unit II Lecture 5

Defn Nociception Nociception is the recieving of signals in the CNS sent due to tissue damaging stimuli
Defn Pain An unpleasant sensation from a specific region of the body. Does NOT always begin with nociception.
What other sensation is closely related to nociception? itch
Some pain does this while other pain serves no real purpose. Acts as a warning preventing further damage to tissues (burned mouth on hot chocolate.
What types of pain serve no real purpose? inflammatory, neuropathic, surgical
What are the receptors affiliated with the ALS in the skin? Free nerve endings
What specific fiber type is stim by sharp objects that pinch or penetrate the skin? What class of nociceptors do they belong to? What don't they like? Adelta fibers. Mechanical nociceptors. Don't like anything that can break the skin
Explain the threshold level for nociceptors They have a very HIGH threshold
What are the two major classes of nociceptors? Mechanical and Polymodal nociceptors
What do polymodal nociceptors respond to? What don't they like? What is special about what stimulates them? High intensity mechanical stimuli, chemical and thermal. Don't like anything with potential to damage the skin. They have MANY adequate stimuli!!
What does Capsaicin do? What fibers does it act on? causes a painful heat. acts on C fibers
What fiber type is associated with polymodal receptors? With mechanical receptors? C fibers. Adelta
C fiber/polymodal receptors can undergo what process? (some Adeltas do too) sensitization. Stimulation over a long period of time enhances their response to subsequent stimuli
True/False: Nociceptors are found within visceral organs True
What is TRPV-1? Where is it expressed? What stimulates it? An ion channel in some nociceptors (Adelta and C fibers ONLY) that is opened in response to noxious heat (or capsaicin.
You hit your finger with a hammer. You get the initial "fast" pain and then a dull "slow" aching pain for the next few days. What fibers mediate which responses? Fast: Adelta, Slow: C
Disease can be causes when children are born without this type of fiber. What stimuli are they insensitive to? C fibers. Frequently also have autonomic problems. Thermal, and noxious stimuli
See drawing for pathway!
Nociceptive primary afferent neurons use what as NTs? What ones does Adelta use? C use? glutamate and substance P. C uses both, Adelta uses glutamate only
What are the receptors that respond to the NTs released by primary nociceptors? What kind of stimulatory affect do the NT's have on the postsynaptic fibers? AMPA and NMDA. Causes EPSPs!
What causes C fibers to secrete Subs P? Prolonged, high intensity stimulation
What is syringomyelia? Bilateral loss of pain and temp with UNILATERAL compression or transection! Occurs if compression is where 2nd neuron in ALS cross in anterior commissure (such as in central canal swelling)
If you get an infarct in the anterior spinal arteries, what senses are affected? Pain, and temp. ALS is affected due to the proximity of the anterolateral funiculi. Even though Vent. SCT and CCT are there, propr. and touch are spared b/c DCML is ok
How does the brain and sc modulate pain signals? What circuits are there? Pain signals to brain/brainstem from ALS. Circuits descend and inhibit nociceptors: periaquaductal gray matter, and Locus ceruleus
Give the pathway for periaquaductal gray matter inhibition of pain. What NT does it use? Start periaquaductal gray matter -> to nucleus raphae magnus in medulla -> gives off seritonergic neuron running in dorsolateral funiculus to dorsal horn & inhib 2ndary nocicept w/ seritonin
Give the pathway for Locus ceruleus inhibition of pain. What NT does it use? Pons sends neuron through dorsolateral funiculus to dorsal horn -> inhib 2ndary nociceptor with NE
Pain inhibition pathways from brainstem can inhib nociceptor signals but not tactile signals. This is cld: Analgesia
what is enkephalin? Enkephalin is an opioid secreted in response to sim from locus cereulus or periaqu. to inhib pain.
How does enkephalin do the presynaptic effect? It decreases entry of Ca++ into primary nociceptor terminal, decreasing the amt of NT it secretes (less ESPS's)
How does enkephalin do the postsynaptic effect? It acts on K+ channels in the 2ndary nociceptor neuron and causes them to open. Causes a hyperpol in the cell mem, and so it can't produce AP
Created by: StudyBuddies