Cardiac Muscle Excitation-Contraction Coupling

Practice: Epinephrine is a hormone (and drug) that binds to β1 adrenergic receptors on cardiac contractile cells. Binding of epinephrine to β1 receptors activates an intracellular signaling cascade that increases the Ca2+ conductance of both L-type Ca2+ channels (LTCCs) and ryanodine receptors (RyRs). Which of the following is the likely effect of epinephrine on the contraction force generated by cardiac contractile cells?

Practice: Epinephrine is a hormone (and drug) that binds to β1 adrenergic receptors on cardiac contractile cells. Binding of epinephrine to β1 receptors activates an intracellular signaling cascade that increases the activity of the sarcoplasmic reticulum/endoplasmic reticulum Ca2+ ATPase (SERCA). Which of the following is the likely effect of epinephrine on the contraction duration of cardiac contractile cells?

Practice: Digoxin is a drug that (indirectly) inhibits the activity of the Na+/Ca2+ Exchanger (NCX) in the membranes of cardiac contractile cells. Which of the following is the likely effect of digoxin on the contraction force generated by cardiac contractile cells?