The Physiology of Pain (karius) Flashcards
how is pain different from all other senses
sensation is elicited by multiple stimuli
it pre-empts all other signals
fast pain is associated with
fast pain
slow pain is characterized as
dull or achy,
often occurs after the injury
what kind of neurons are many of the pain receptors
bare nerve endings with specialized ion channels that open in response to specific stimuli
2 types of bare nerve ending fibers
A(delta) fibers: small, sparsely myelinated, fast sharp pain
C fibers: unmyelinated fibers with dull pain
types of nociceptors (4)
sensitive to thermal and mechanical stimuli (majority)
sensitive only to thermal stimuli
sensitive only to mechanical stimuli
silent/sleeping (not active under most normal conditions)
many mixed modality nociceptors also express a mechanosensitive ____ channel called what
-mutations can lead to what
Na+ channel called SCN9A or Na1.7
- mutations in this channel lead to absence of pain sensation
- another class of mutation produces paroxysmal pain syndrome
nociceptors express what kind of additional type of receptor
ligand gated
ligand gated receptors on nociceptors bind what molecules
-bidning causes what?
substance P
the kinins
ATP
H+
-when bind, change sensitivity of nociceptors and activate silent nociceptors
what is the source of the ligands that bind nociceptors
damaged tissue, recruited WBC, activated nociceptors
-release to periphery as well as spinal cord
A(delta) neurons release what NT and act on _____ receptors
EAA, non-NMDA
NTs from C fibers released
substance P
EAA
nociceptors that travel with the spinoreticulothalamic path are ___ fibers and take what path
slow pain
-synapse on interneuron in SC, cross and acend to reticular formation
synapse at the interneuron is site for what modulation
local (gate theory)
descending (opioid pathways)
what do visceral afferents travel with
autonomic nerves
what part of cortex plays a role in localizing pain
S1 and S2
what is the insular cortex important for with pain
interpretation of nociceptive inputs
-processes info about internal state of body
contributes to autonomic response to pain
-integrates all signals related to the pain (asymbolia)
how does lesion in any one area effect pain
does not abolish the ability to experience pain but experience is changed
nociceptive inputs to amygdala
important in activating/producing the emotional components inherent in sensation of pain
visceral nociceptors traveling with ___ ___ have additional synapses within the
autonomic nerves
-hypothalamus and medulla
additional visceral nociceptors synapses function
form basis of the physiological changes associated with visceral pain, including diaphoresis and altered BP
gate theory of pain basis
based in part on the observation that other somatic input can alleviate pain (rubbing the area)
gate theory of pain steps
1) activate A(beta) fiber by normal stimuli, has branch that travels via dorsal columns, but also branches within spinal cord
2) A(beta) fiber releases EAA and activates inhibitory interneuron
3) inhibitory interneuron releases glycine to inhibit acitivty of 2nd order neuron in pain path
4) end result: rubbing area of skin activated by A(beta) fiber will reduce the sensation of pain
pysiological mod of pain: descending influences steps
1) neurons in periaqueductal gray activated by numerous inputs: opiates, EAA and cannibinoids
2) neurons from PAG travel to midline Raphe nuclei and release enkephalins, activate raphe neurons
3) axons from raphe neurons travel to SC and release serotonin–>activates inhibitory interneurons, causing them to release opiates
4) opiates released by interneuron activate mu receptors on presynaptic terminal of C fiber
5) this produces pre-synaptic inhibition that reduces release of substance P from nociceptor and reduces pain transmission
