BIO 208 Lecture Notes - Lecture 17: Afferent Nerve Fiber, Nociceptor, Group C Nerve Fiber
25 Feb 2018
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Novocain, procaine: second pain results from conduction in unmyelinated c- fibers, small fibers are selectively blocked by (cid:498)local anesthetics(cid:499)- e. g. , no pain from stimulating a fibers. Only a tingling or (cid:498)pins and needles(cid:499): a-delta and c fibers are slowest, once a-delta is reaches, you feel pain. Takes longest to get to c and a- Nociceptors responsible for pricking (1st) pain (a- fibers(cid:524) have no opiate receptors. Thus to reduce pain without effects on the stomach it is best to block cox2 only (located near nociceptor endings). Vioxx/celebrex is cox 2 inhibitor- but cardiovascular side effects: tylenol (acetominophen) inhibits cox3 located in cns. It may play a part in memory formation. Persistent pain: central sensitization to a burn (in the surrounding areas); has a lower threshold to pain- changes also occurring in the brain (windup, ltp, synaptic strength all lead to central sensitization) Immediately after amputation patients feel a clenched fist with nails digging into the skin- very painful.
