ANATOMY

Detailed explanation-1: -The heart is regulated by both neural and endocrine control, yet it is capable of initiating its own action potential followed by muscular contraction. The conductive cells within the heart establish the heart rate and transmit it through the myocardium.

Detailed explanation-2: -One other distinct feature of cardiac muscle fibers is that they have their own auto rhythmicity. Unlike smooth or skeletal muscle which require neural input for contraction, cardiac fibers have their own pacemaker cells like the sinoatrial (SA) node that spontaneously depolarizes.

Detailed explanation-3: -Which of the following is true of the cardiac action potential? You correctly answered: b. The cardiac action potential is longer than the skeletal muscle action potential.

Detailed explanation-4: -The cardiac action potential is a measurement of the membrane potential waveform of the cardiac myocytes signifying the electrical activity of the cell during the contraction and relaxation of the heart. Specific ionic currents contribute to each phase of the cardiac action potential (see Fig. 24-10).