Question

Which of the following statement(s) is (are) true? A. The force the heart must overcome in order to pump blood is known as the its stroke volume. B. The term preload refers to a tension, or pressure, that the left ventricle must develop in order for the heart to function properly. C. The preload and afterload are the primary factors that cause the heart rate to change. D. Contractility of the heart muscle refers to the force of contraction that this muscle can exert. E. Both C and D are true.

Answer 1

Answer:  D. Contractility of the heart muscle refers to the force of contraction that this muscle can exert.

Explanation:

The myocardial contractility is ability of the heart muscles to contract. This is achieved by the forces which develop between the contracting muscles caused by the filaments of actin and myosin.

The degree of binding of the muscle filaments dependents upon the calcium ion concentration. These actions are controlled in vivo by the sympathetic nervous system. It is driven by the release of the catecholamine, which is a process which determines the calcium ion concentration inside the cytosol of the muscles of the heart.