Define the term 'cardiac output' and describe the two components which comprise it.

Cardiac output is a term used in cardiovascular physiology that describes the volume of blood being pumped by the heart, in particular by a left or right ventricle, per unit time. It is usually measured in liters per minute (L/min).

Cardiac output is determined by two components: heart rate and stroke volume.

1. Heart Rate (HR): This is the number of heartbeats per minute. In a healthy adult at rest, the heart rate is typically between 60 to 100 beats per minute.

2. Stroke Volume (SV): This is the amount of blood pumped by the left ventricle of the heart in one contraction. The stroke volume and the heart rate determine the cardiac output. A normal adult has a stroke volume of about 70 mL.

Therefore, the cardiac output (CO) can be calculated using the formula: CO = HR x SV.