KINE 3012 Chapter Notes - Chapter 1.1: Pacemaker Potential, Atrioventricular Node, Sinoatrial Node
11 Mar 2018
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Pace(cid:373)aker pote(cid:374)tial: occurs in sa node self excitation of sa, sa called pacemaker b/c it regulates heartbeat, slope of pacemaker potential determines rate of ap generation. Without external input heart beats 100 aps/minute: gradual increase in membrane potential is pacemaker, calcium is high outside cell. Na+ & ca+ into cell; k+ diffuses out of cell. Cardiac action potential: brings membrane potential to threshold of sa node, progressive drop in k+ permeability. K+ channels close so no k+ can move out: increase in na+ permeability. Opening of f-type na+ channels: increase in ca2+ permeability. Opening of t-type ca2+ channels (voltage gated: cause membrane potential to rise. reaches threshold which gives ap, l-type ca2+ channels open. Calcium rushes in really fast to high max ap (peak). Ca2+ channels immediately close: k+ channels open to decrease membrane potential k+ leaves cell to restore potential, slow rise is called pace maker.
