Compare And Contrast Cardiac And Smooth Muscle

Compare and contrast cardiac and smooth muscle.
In cardiac muscle, each heartbeat is triggered by the hearts own pacemaker cells, which initiate electrical discharge and when this reaches the contractile muscle cells (the cardiomyocytes), they create an action potential which increases the concentration of calcium ions into the cell. Calcium ions play a key role in activating what is known as the contractile machinery – the actin and myosin filaments. The cardiac action potential, unlike other forms of muscular contraction, will last roughly as long contraction. This is shown below, depolarisation is followed by an unusual plateau, and the cardiac action potential can be split into five main phases.
Cardiomyocytes are also electrically coupled – so they all contract and relax in unison, enabling for a unified response in the heart (i.e. the atrial and ventral muscles contract in unison) In cardiac cells, the
Phase 3 – As the plateau continues, the potassium conductance again begins to increase, due to the opening of delayed rectifier potassium channels – these act in a delayed or slow manner. As repolarisation occurs, the conductance of potassium ion channels decrease, causing final repolarisation. The size of the potassium ion current influx affects the duration of the plateau.
The refractory period is cardiomyocytes is during the depolarisation phase, where the cardiomyocyte cannot be electrically excited at all, this is called the absolute refractory period. As depolarisation occurs, when it reaches around -50mv, it enters its relative refractory period, where the cardiomyocyte can be excited, but only with a stimulus which is far stronger than the initial stimulus.
Excitation-contraction