Chapter 12-2 pages 413-416 By Isaac, Noah and Nick

Cardiac Muscle Cells In one heartbeat, the entire heart contracts in a coordinated manner so blood flows in the correct direction at the right time Have longer refractory period than skeletal muscle Relax long enough so that the hearts chambers can refill with blood

Cardiac Muscle Cells Contractile Cells - produce a powerful contraction that propels blood Conducting System – controls and coordinates the activities of the contractile cell

Contractile Cells Form the bulk of the hearts muscle tissue Forms 99% of all cardiac muscle cells

Contractile Cells Rapid Depolarization Plateau Repolarization Voltage gated sodium channels open, and the influx of sodium ions rapidly depolarizes the sarcolemma Plateau As the cell begins to actively pump sodium ions out, voltage gated calcium channels open and extracellular calcium ions enter the sarcoplasm Repolarization As the calcium channels begin to close, potassium channels open and potassium ions rush out

Conducting System

Conducting System Conducting Cells – distribute the contractile stimulus to the general myocardium Nodal Cells – responsible for establishing the rate of cardiac contraction Pacemaker Cells – nodal cells that reach threshold first