An increase in cardiac output should _ mean arterial pressure. increase decrease
The correct answer and explanation is:
Answer: An increase in cardiac output should increase mean arterial pressure.
Explanation:
Mean arterial pressure (MAP) is a critical measure of the average pressure in a person’s arteries during one cardiac cycle. It represents the driving force that pushes blood through the systemic circulation, delivering oxygen and nutrients to tissues.
The formula that relates MAP to cardiac output (CO) and systemic vascular resistance (SVR) is: MAP=CO×SVR\text{MAP} = \text{CO} \times \text{SVR}
- Cardiac Output (CO) is the volume of blood the heart pumps per minute. It is calculated as: CO=Heart Rate×Stroke Volume\text{CO} = \text{Heart Rate} \times \text{Stroke Volume}
- Systemic Vascular Resistance (SVR) refers to the resistance blood encounters as it flows through the systemic blood vessels.
When cardiac output increases, assuming systemic vascular resistance remains constant, there is more blood volume being pushed into the arteries every minute. This increase in volume causes arterial pressure to rise, leading to an increase in mean arterial pressure.
For example, during exercise, the heart pumps more blood per minute to meet the increased oxygen demands of muscles. This increase in cardiac output elevates arterial pressure temporarily. The body regulates this carefully through mechanisms such as vasodilation, which can reduce vascular resistance to balance the pressure increase.
If the heart pumps more blood but the vessels do not dilate (i.e., SVR stays the same or increases), then MAP will increase. Conversely, if SVR decreases significantly, it might offset the increased cardiac output, keeping MAP stable or even reducing it.
In clinical settings, abnormal increases in cardiac output (such as in hyperthyroidism or certain heart conditions) can cause elevated blood pressure, which increases the workload on the heart and risks damage to vessels and organs.
In summary, an increase in cardiac output generally leads to an increase in mean arterial pressure, provided that vascular resistance does not decrease enough to counteract this effect.