Download Chapter 12-2 pages 413-416

By Isaac, Noah and Nick
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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
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Contractile Cells - produce a powerful
contraction that propels blood
Conducting System – controls and coordinates
the activities of the contractile cell
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Form the bulk of the hearts muscle tissue
Forms 99% of all cardiac muscle cells
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Rapid Depolarization
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Plateau
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Voltage gated sodium channels open, and the influx
of sodium ions rapidly depolarizes the sarcolemma
As the cell begins to actively pump sodium ions out,
voltage gated calcium channels open and
extracellular calcium ions enter the sarcoplasm
Repolarization
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As the calcium channels begin to close, potassium
channels open and potassium ions rush out
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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