The Cardiac Cycle III: Volumes in the Left Ventricle

Practice: Exercise increases the amount of blood that returns to the heart between beats. Which of the following is directly changed by exercise-mediated increases in venous return?

Practice: Epinephrine is a hormone that binds to β1 adrenergic receptors on cardiac contractile fibers. The activation of β1 adrenergic receptors causes an increase in the “contractility” of cardiac contractile fibers—the fibers contract more forcefully. As a result, the heart ejects more blood per beat and leaves less “leftover.” Which of the following is directly changed by epinephrine-mediated increases in cardiac contractility?