The key word to consider when thinking about the control of blood flow and arterial blood pressure (ABP) is ‘integration’. The body has developed a large number of integrated homeostatic mechanisms in order to keep ABP and flow at around constant levels, with the aim of maintaining adequate perfusion of the vital organs both at rest and in situations where there is a change in environment or workload. Maintenance of normal ABP is mainly dependent on the balance between cardiac output and peripheral vascular resistance (PVR), related by the equation:
Mean ABP = Cardiac output × PVR