Pain and Analgesia Flashcards
what is pain?
an unpleasant sensory and emotional experience associated with actual or potential tissue damage
are pain and nociception the same?
NO! pain cannot be inferred solely from activity in sensory neurons, and pain has a consious component
what is nociception?
the neural process of encoding noxious stimuli
what are the 3 big categories of pain control?
- anti nociception (abscence of response to a normally painful stimulus, aka there is an inability to respond but there could still be pain)
- analgesia (abscence of pain in response to a stimuli which would normally be painful)
- general anesthesia (drug induced unconsiousness by reversable depression of the CNS and perception)
nociceptors are capable of detecting different types of stimuli, such as: __________. Most are _______
- mechanical
- chemical
- thermal
polymodal, meaning they can detect multiple types of stimuli
which sensory nerve fibers are myelinated and which are not?
A fibers are myelinated (including A alpha, beta, and delta fibers)
C fibers are not myelinated
which sensory nerve fibers can perceive nociception?
A delta and C fibers. A delta is fast ad C is slow
considering A fibers are faster conducting than C fibers, what kind of pain does each sense?
A fibers: sharp, well localized pain (skin, SQ, fascia, bone)
C fibers: dull, diffuse pain (muscle, viscera)
what is the primary excitatory neurotransmitter released by A and C fibers?
glutamate (some C fibers can express substance P)
explain inflammatory soup and why inflammation can be a bad thing sometimes!
nociceptors are very sensitive to inflammatory mediators like cytokines, and when these mediatorys are around they increase nociception. The stimulation of these nociceptors also increases local production of inflammatory mediators which makes a positive feedback loop.
what does inflammation do to the pain threshold? how about analgesics?
inflammation will decreases the pain threshold, making it easier to feel pain
analgesic therapy will increase the pain threshold, which means it takes more to feel or preceive a certain level of pain
define hyperalgesia and allodynia
hyperalgesia: increased sensitivity to noxious stimuli
allodynia: when normally non noxious stimuli become capable of eliciting a pain response
explain where each of the following drug classes works at the CNS levels:
- antidepressants and opiods
- opiods and alpha 2 agonists
- local anesthetics
- works at the level of the cerebral cortex
- works at the level of the spinal cord (modulation)
- works at the level of transmission of sensory nerves
explain what wind up is
spinal facilitation of pain, aka high frequency action potentials train the second order neurons to respond more vigorously to subsequent stimulation, the increase in pain intensity over time when a given stimulus is delivered repeatedly above a critical rate.
does general anesthesia prevent wind up?
no! this is why you MUST provide analgesia as well as anesthesia
explain the process step by step of what happens at the receptor/nerve level of wind up. where does this process all happen?
high frequency of action potentials in primary afferent nerves–>increased glutamate and other neurotransmitters–>activation of normally inactive NMDA receptors–>influx of calcium into the post synaptic cell–>upregulation of receptors on the post synaptic membrane –>this nerve becomes hypersensitive
this all happens at the level of the dorsal horn of the spinal cord
explain why you should do pre-emptive analgesia
because we know pain leads to increased sensitivity which will lead to wind up, so if we use pre-emptive analgesia we can control the pain before it actually starts
are anesthetics good analgesics too?
NO this is why you MUST provide analgesia in surgery before your patient wakes up!
what is a descending inhibitory pathway in regards to pain?
these are descending pathways from the brain that modulate pain by either excitatory action or inhibatory action via endogenous/exogenous opiods. Whether they are pro-nociception or anti-nociception depends on the neurotransmitter, for example norepinephrine is always anti nociception, but dopamine and serotonin can be both.