Which of the Following Statements About Membrane Potentials in Different

Multiple Choice

Which of the following statements about membrane potentials in different types of cardiac cells is TRUE?

A) Myocardial cells have a resting membrane potential of about -90 mV; pacemaker cells do not have a true resting membrane potential.
B) Once threshold depolarization is reached in both myocardial and pacemaker cells, the rapid upswing of the action potential is caused by the opening of voltage-gated Na⁺ channels
C) Voltage-gated transient (T-type) Ca²⁺ channels are present in all of the different types of cells of the heart.
D) There are no L-type Ca²⁺ channels in cardiac muscle cells.
E) The upstroke of the action potential is steeper in SA node cells than it is in Purkinje cells.