Which of the following factors regulates blood pressure?

Blood pressure is primarily regulated by two major factors: cardiac output and total peripheral vascular resistance. Cardiac output refers to the volume of blood the heart pumps per minute, which is determined by heart rate and stroke volume. Total peripheral vascular resistance is the resistance to blood flow provided by the blood vessels, which can be affected by various factors including vessel diameter and blood viscosity.

When cardiac output increases, typically due to higher heart rate or increased stroke volume, there is a corresponding rise in blood pressure because more blood is being pumped into the arterial system. Conversely, if total peripheral vascular resistance decreases—such as during vasodilation—this can also impact blood pressure regulation. Therefore, the relationship between cardiac output and total peripheral vascular resistance forms a crucial part of the equation that determines blood pressure.

In contrast, while blood volume and heart rate are related to the regulation of blood pressure, they are not as directly impactful in combination as cardiac output and total peripheral vascular resistance. Similarly, physical activity can influence blood pressure, but it is not a regulatory factor in the direct sense. Peripheral resistance and oxygen levels may have some associations with blood pressure, but they do not encapsulate the primary regulatory mechanisms as accurately as cardiac output and total peripheral vascular resistance.