A heart murmur is a defect in one or more of the valves that allows backflow of blood. Serious defects are usually corrected by surgical replacement of the valve. The number of heartbeats per minute. Usually measured by taking the pulse. It is not uncommon for heart rates to change during the day.
Stroke volume is the amount of blood pumped by the left ventricle each time it contracts.
The average human stroke volume is about 75 ml per beat. The cardiac output of an average human is 5.25 L per minute. Located in the right atrium wall near the entrance of the superior vena cava. The SA node is composed of specialized muscle tissue which has characteristics of both muscle and nerve tissue. Contraction of the SA node initiates a wave of excitation that spreads rapidly from the node and causes the two atria to contract in unison.