MICROANATOMY

Detailed explanation-1: -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-2: -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. The contractile cells contract and propel the blood.

Detailed explanation-3: -The generation of the action potential and the regional differences that are observed throughout the heart are the result of the selective permeability of ion channels distributed on the cell membrane. The ion channels reduce the activation energy required for ion movement across the lipophilic cell membrane.

Detailed explanation-4: -The correct statement is d. The action potential in the heart generates when the concentration of potassium and sodium ion changes across the cell.