AS OCR Biology-The Heart and the Cardiac cycle

The sequence of events during the beating of the mammalian heart is called the cardiac cycle. On average there are about 70 such cycles per minute in resting humans. The cardiac muscle is myogenic which means it can contract and relax without nervous stimulation, but to ensure that the cycle stays in sequence there is an in built control system. The cycle is initiated in a special part of the muscle in the wall of the right atrium called the Sino Atrial Node. This sets up a wave of excitation causing the atria to contract. After a delay about 0.6 seconds the wave of excitation passes to the ventricles via the Atrial Ventricular Node situated in the Septum…