PHSI2005 Final: cardiac cycle 2

• School: University of Sydney
• Department: Physiology
• Course: PHSI2005
• Professor: phsi2005

Document Summary

At the end of the lecture you should be able to: explain how the structural properties of cardiac muscle permit the rapid spread of action potentials throughout the heart. Sino-atrial nodal cell (cid:120) no resting membrane potential instead, there is a pacemaker potential that spontaneously depolarises. In comparison to other aps, the sa node ap has a more gradual upstroke (cid:120) (cid:120) while the upstroke in skeletal muscle is dependent on na+ influx, the upstroke of cardiac pacemaker cells is dependent on ca2+ influx. The greater the intracellular [ca2+], the greater the force of contraction. (cid:120) (cid:120) If cardiac muscle cell is placed into a calcium free solution, it will not contract because contraction relies on ca2+ induced-ca2+ release. If skeletal muscle cell is placed into a calcium free solution, it would because it relies on sarcoplasmic stores of ca2+ for cross-bridge cycling.