a&p2 test 2

The long plateau phase of the cardiac muscle action potential is due to -calcium channels remaining open. -increased membrane permeability to sodium ions. -increased membrane permeability to potassium ion. -movement of fewer sodium ions across the cell membrane. -decrease in the amount of calcium diffusing across the membrane.

calcium channels remaining open.

As a result of the long refractory period in the cardiac action potential, cardiac muscle cannot exhibit tonus. tetany. treppe. fatigue. recruitment.

tetany

Tetanic muscle contractions don't occur in a normal cardiac muscle because -cardiac muscle tissue contracts on its own. -neural stimulation is lacking. -the refractory period lasts until the muscle relaxes. -potassium channels outnumber sodium channels. -the refractory period ends before the muscle reaches peak tension.

the refractory period lasts until the muscle relaxes.

The normal pacemaker of the heart is located in -the atrioventricular node. -the sinoatrial node. -the wall of the left ventricle. -the Purkinje fibers. -both the left and right ventricles.

the sinoatrial node.

In cardiac muscle, the fast depolarization phase of the action potential is the result of -increased membrane permeability to potassium ions. -decreased membrane permeability to sodium ions. -increased membrane permeability to chloride ions. -increased membrane permeability to sodium ions. -decreased membrane permeability to calcium ions.

increased membrane permeability to sodium ions.