BIOL 121 Lecture Notes - Lecture 23: Purkinje Fibers, Atrioventricular Node, Pacemaker Potential
Document Summary
Contract ventricles- (from apex to the top) Conduction system- has sa node (up at top), av node (middle right atrium) connects to bundle of his, splits into left and right bundle branch, split into purkinje fibers. Sa node (pacemaker, spontaneously depolarizes) starts a heartbeat, stimulates contraction cells to av valve (critical in conduction pathway), stimulates bundle of his then bude branches to purkinje fibers. Purkinje fibers stimulate contractile fibers backup to create a contraction. Muscle twitch- contraction is maintained for long time. Calcium active as an electrically active ion that influences membrane potentials (used to be just a secondary messenger) Stimulated by depolarization of opening of sodium (na+ channels) opens up calcium channels (l-type, stands for lingering/ late) which do not immediately close back. The plateau of depolarization is cured by potassium channels opening again which causes a repolarization. Refractory period of the heart- can stimulate muscle again because of plateau of depolarization. When it"s impossible for tetany (continuous contraction)
