What two factors generally determine blood pressure?

Blood pressure is primarily determined by two critical factors: cardiac output and resistance to blood flow. Cardiac output refers to the amount of blood the heart pumps in one minute, which is influenced by both stroke volume (the amount of blood ejected with each heartbeat) and heart rate (the frequency of heartbeats). When cardiac output increases, it typically leads to a rise in blood pressure because more blood is being forced into the arteries.

Resistance to blood flow, on the other hand, is largely influenced by the diameter of the blood vessels; narrower vessels create higher resistance, leading to higher blood pressure, while wider vessels lower resistance and can decrease blood pressure. This relationship is described by the equation for blood pressure, which states that blood pressure = cardiac output × vascular resistance.

By understanding these two factors, it's clear why the correct answer emphasizes cardiac output and resistance to blood flow. Increasing either cardiac output or vascular resistance will lead to an increase in blood pressure, whereas decreasing either one could result in lower blood pressure.