BIOL 031 Lecture Notes - Lecture 10: Sinoatrial Node, Action Potential, Cardiac Output

• School: College of The Sequoias
• Department: Biology (BIOL)
• Course: BIOL 031
• Professor: trimble

Document Summary

Needs to contract in a synchronized manner with the pacemaker cells: pacemaker cells set the pace. Phase 0: increased permeability to sodium: rapid upswing of contractile ap is similar to neuronal ap, impulse from sa node arrives, depolarizes membrane, triggers opening of na channels, membrane becomes more positive, depolarization. Phase 2: increased permeability to calcium, decreased permeability to potassium: plateau phase, keep membrane in depolarized state. Phase 3: increased permeability to potassium, decreased permeability to calcium: channels open and repolarizes. Phase 4: resting membrane potential: all permeabilities are at resting values, closer to equilibrium of potassium. Skeletal muscle is short, so the contraction occurs after the action potential has arrived. If a muscle is stimulated repetitively, the individual twitches become indistinguishable, tension rises swiftly and smoothly: complete tetanus. However, do not want this in cardiac muscles!!!!! Cardiac muscles have long duration of action potential. Summation cannot occur because the duration is so long.