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Stack #215245
Neuro Unit II Lecture 5
| Question | Answer |
|---|---|
| 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 |
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