- Slow wave potential
In
neurobiology , a slow wave potential is a depolarization in amyocyte cell which does not cause a contraction oraction 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 stimulusGastrointestinal 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] Aslow wave threshold must be reached before a slow wave potential can propagate. Theamplitude andfrequency of the wave are modulated by intrinsic (Auerbach's plexus &Meissner's plexus ) or extrinsic (Sympathetic nervous system &Parasympathetic nervous system ) innervation or byhormone s. Excitatory compounds includeacetylcholine andSubstance P , inhibitory includevasoactive intestinal peptide andnitric 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 thecolon 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]References
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