Slow wave potential

In neurobiology, a slow wave potential is a depolarization in a myocyte cell which does not cause a contraction or action potential.

Slow wave potentials are unstable resting membrane potentials that continuously cycle through depolarization- and repolarization phases. However, not every cycle reaches depolarization threshold and thus an action potential (AP) will not always fire. Owing to temporal summation, however, cell membrane depolarization will periodically reach depolarization threshold and an action potential will fire, triggering contraction of the myocyte. It is important to note that slow waves are intrinsic, or they do not rely on exogenous stimulus, but they can be altered by an exogenous stimulus

Gastrointestinal Smooth Muscle

In the gastrointestinal smooth muscle, a slow wave originates in the cells of Cajal as the Basic Electrical Rhythm. Loss of these cells stops the propagation of a slow wave potential and thus, gut motility. [Huizinga. Neural Injury, Repair, and Adaptation in the GI Tract IV. Pathophysiology of GI motility related to interstitial cells of Cajal. Am J Physiol Gastrointest Liver Physiol 275: G381-G386, 1998;0193-1857/98 http://ajpgi.physiology.org/cgi/content/abstract/275/3/G381] A slow wave threshold must be reached before a slow wave potential can propagate. The amplitude and frequency of the wave are modulated by intrinsic (Auerbach's plexus & Meissner's plexus) or extrinsic (Sympathetic nervous system & Parasympathetic nervous system) innervation or by hormones. Excitatory compounds include acetylcholine and Substance P, inhibitory include vasoactive intestinal peptide and nitric oxide. [Pathophysiology. Porth. 7th Ed. pg.875-878 Published by Lippincott, Williams & Wilkins. ISBN 0781749883]

The frequency of slow waves also varies between sections of the intestinal tract. In small intestine, they occur at a rate of 10-20 per minute, while in the colon they occur at a slower rate of 3 to 8 per minute. [R. Bowen. Electrophysiology of Gastrointestinal Smooth Muscle. November 23, 1996. Accessed February 12, 2008. http://www.vivo.colostate.edu/hbooks/pathphys/digestion/basics/slowwaves.html]

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