Cardiovascular centre is detected by baroreceptors in the aortic sinuses or carotid sinuses, the cardiovascular centre affects changes to the heart rate by sending a nerve impulse to the cardiac pacemaker (or SA node) via sympathetic fibres (to cause faster and stronger cardiac muscle contraction) and the vagus nerve (to cause slower and less strong cardiac muscle contraction). The cardiovascular centre also increases the stroke volume of the heart (that is, the amount of blood it pumps). These two changes help to regulate the cardiac output, so that a sufficient amount of blood reaches tissue. Hormones like epinephrine and norepinephrine can affect
Cardiac action potential Cardiac action potential The cardiac action potential is a brief change in voltage (membrane potential) across the cell membrane of heart cells. This is caused by the movement of charged atoms (called ions) between the inside and outside of the cell, through proteins called ion channels. The cardiac action potential differs from action potentials found in other types of electrically excitable cells, such as nerves. Action potentials also vary within the heart; this is due to the presence of different ion channels in different cells (see below). Unlike the action potential in skeletal muscle cells, the cardiac action potential is