The Physiology of Pain (karius)

Question 1

how is pain different from all other senses

Answer 1

sensation is elicited by multiple stimuli

it pre-empts all other signals

Question 2

fast pain is associated with

Answer 2

fast pain

Question 3

slow pain is characterized as

Answer 3

dull or achy,

often occurs after the injury

Question 4

what kind of neurons are many of the pain receptors

Answer 4

bare nerve endings with specialized ion channels that open in response to specific stimuli

Question 5

2 types of bare nerve ending fibers

Answer 5

A(delta) fibers: small, sparsely myelinated, fast sharp pain

C fibers: unmyelinated fibers with dull pain

Question 6

types of nociceptors (4)

Answer 6

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)

Question 7

many mixed modality nociceptors also express a mechanosensitive ____ channel called what
-mutations can lead to what

Answer 7

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

Question 8

nociceptors express what kind of additional type of receptor

Answer 8

ligand gated

Question 9

ligand gated receptors on nociceptors bind what molecules

-bidning causes what?

Answer 9

substance P
the kinins
ATP
H+

-when bind, change sensitivity of nociceptors and activate silent nociceptors

Question 10

what is the source of the ligands that bind nociceptors

Answer 10

damaged tissue, recruited WBC, activated nociceptors

-release to periphery as well as spinal cord

Question 11

A(delta) neurons release what NT and act on _____ receptors

Answer 11

EAA, non-NMDA

Question 12

NTs from C fibers released

Answer 12

substance P

EAA

Question 13

nociceptors that travel with the spinoreticulothalamic path are ___ fibers and take what path

Answer 13

slow pain

-synapse on interneuron in SC, cross and acend to reticular formation

Question 14

synapse at the interneuron is site for what modulation

Answer 14

local (gate theory)

descending (opioid pathways)

Question 15

what do visceral afferents travel with

Answer 15

autonomic nerves

Question 16

what part of cortex plays a role in localizing pain

Answer 16

S1 and S2

Question 17

what is the insular cortex important for with pain

Answer 17

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)

Question 18

how does lesion in any one area effect pain

Answer 18

does not abolish the ability to experience pain but experience is changed

Question 19

nociceptive inputs to amygdala

Answer 19

important in activating/producing the emotional components inherent in sensation of pain

Question 20

visceral nociceptors traveling with ___ ___ have additional synapses within the

Answer 20

autonomic nerves

-hypothalamus and medulla

Question 21

additional visceral nociceptors synapses function

Answer 21

form basis of the physiological changes associated with visceral pain, including diaphoresis and altered BP

Question 22

gate theory of pain basis

Answer 22

based in part on the observation that other somatic input can alleviate pain (rubbing the area)

Question 23

gate theory of pain steps

Answer 23

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

Question 24

pysiological mod of pain: descending influences steps

Answer 24

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

Question 25

deep pain

Answer 25

associated with periosteum, ligaments
usually dull, achy
few A delta fibers
many C fibers
associated with muscle spasms

Question 26

muscle pain cause what gropus and fast or slow pain

Answer 26

cause: usually injury or ischemia during contraction
- both group II and IV fibers present
- both fast and slow pain

Question 27

visceral pain location, receptors, other

Answer 27

poorly localized
few receptors (almost all group IV)
stretch receptors
often referred

Question 28

referred pain: example of heart attack and left shoulder pain

Answer 28

previous expreience has taught the brain that the shoulder is more likely to experience pain than the heart

nociceptors may converge on same interneuron in spinal cord

brain is left with its best guess