BIOL 2P93 Lecture Notes - Migrating Motor Complex, Constipation, Sacral Plexus
4 Feb 2013
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Document Summary
The gi tract can be seen as a series of pumps, conduits, reservoirs, and gates. This allows the tract to perform several functions such as propulsion, grinding, mixing, and compartmentalization. There are 2 types of enteric smooth muscle contractions. Phasic contractions result from momentary stimulation and are used for pumping. Tonic contractions result in continuous pressure such as in sphincters, and must be relaxed to allow gating. Neural input for most of the gi tract is mostly autonomic. The parasympathetic side stimulates the gi tract in general, and its nerves enter through the vagus and sacral plexus. The sympathethic side is inhibitory in general, and nerves enter through the sympathetic ganglion. The myenteric plexus is the intrinsic nervous system of the gut and while it is modulated by the. Some gi muscle is directly innervated and others are indirectly innervated. The pattern of contraction determines the result.
