Pain Flashcards
Physiology of Pain
Nociceptors
Nociceptors
i. Specialized “free” neurons
ii. Respond to potentially damaging stimuli
iii. Most not myelinated
iv. When does it cross contralaterally?
Nociceptors
- They cross over immediately, at the spinal cord, which
means they evolved at different time from myelinated
neurons because they cross at the medulla
Several brain structures involved
Anterior cingulate cortex (emotional)
1. Tylenols studies
a. Looks at students who have been dumped recently,
one group took max dose of tylenol once a day for
a month while the other group was the control and
took a placebo.
b. Those who took tylenol were significantly less
depressed in comparison to those who took
placebo. This was replicated as well and same
results were found.
Somatosensory Cortex (sensory)
- Helps find where pain is located
PAG
- Has receptors for substance P, big dopamine producing
center
Gate Theory
Why does rubbing a wound relieve pain?
Why does rubbing a wound relieve pain?
i. Small C fibers (nociceptors) activated during pain;
ii. Regular large fibers do not carry pain
iii. Rubbing activates large fibers which covers up the pain coming
from the small C fibers
Gate Theory
- Closes pain “gate” in spinal cord
- Gate theory probably BS
- Better explanation: increases endorphins
Stimulation produced analgesia
- Based on same idea on rubbing something constantly
- Transcutaneous electrical nerve stimulation (TENS)
“Congenital insensitivity to pain with anhidrosis” (CIPA)
a. They don’t have any nociceptors or c nerve fibers
b. Cannot sweat
c. Doesn’t sneeze or cough, never scratches an itch
d. Type of HSAN, another name for this
Endorphins
a. Bind to PAG in midbrain
b. Block release of “substance P” by nociceptors
c. Opiates bind to same receptors
i. Morphine, oxycodone, codeine, fentanyl
Other ways to increase endorphins?
i. Exercise
ii. Laughter
iii. Orgasm
iv. Acupuncture?
