Slow wave potential originates in which pa of intestine:
(A) Interstitial cells of Cajal (B) Parasympathetic neurons (C) Smooth muscle cells (D) Myentric plexus
(A) INTERSTITIAL CELLS OF CAJAL: - These cells synapse with both smooth muscle and neurons of enteric nervous system - They are Pacemaker cell of G.I tract. - Smooth muscle of G.I.T have 2 basic types of electric waves. 1. Slow waves 2. Spikes Slow waves: - Most gastro intestinal contractions occur rhythmically & this rhythm is determined mainly by frequency of 'slow waves' - These are not action potentials, instead they are slow undulating changes in resting membrane potential - These waves are caused by complex interactions among smooth muscle cells & interstitial cells of cajal. - Slow waves usually do not themselves cause muscle contraction (except in stomach) instead they mainly excite appearance of intermittent spike potential & spike potentials in turn actually excite muscle contraction. Parasympathetic neurons - depolarize smooth muscle cell & makes muscle fibers more excitable. Smooth muscle contraction occurs in response to entry of calcium ions into muscle fiber. Enteric nervous system composed of 2 plexuses 1. Myenteric plexus / Auerbach's plexus - outer 2. Submucosal Meissner's plexus - inner Myenteric plexus control G.I movements Submucosal plexus control G.I secretions & local blood flow.