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)

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

c. The plateau phase in contractile cells is due to the influx of calcium ions through calcium ion channels.

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

d.The repolarization phase of the contractile cell is due to the potassium ions rushing into the cell through potassium ion channels.

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?

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?