The noncontractile cardiac muscle cells that initiate their own depolarization and cause depolarization of the rest of the heart are called __________.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

e. Open sodium ion channels cause hyperpolarization in pacemaker cells, which triggers HCN channels to open and begins a new action potential.

What are the effects of the plateau phase of the contractile cell action potential?

An experimental toxin makes the refractory period of cardiac muscle cells equal in length to that of skeletal muscle fibers. Predict the consequences of this toxin. (Connects to Chapter 10)

Which of the following correctly identifies a difference between action potentials in cardiac and skeletal muscle?

Calcium ion channels open in response to changes in membrane potential. What type of opening mechanism do calcium ion channels in cardiac muscle exhibit?

Autorhythmicity is a unique feature of cardiac pacemaker cells. What feature of cardiac pacemaker cells allows them to be autorhythmic while other cardiac cells are not?

Cardiac contractile tissue uses sodium, calcium, and potassium channels for depolarization and repolarization. During which phase of the action potential is the calcium channel open?