Final answer:
If cardiac output increases, the peripheral resistance must decrease for arterial blood pressure to remain constant. This is because when the heart pumps more blood per minute, the peripheral resistance needs to decrease to allow for easier blood flow through the blood vessels.
Step-by-step explanation:
If cardiac output increases, the peripheral resistance must decrease for arterial blood pressure to remain constant. When cardiac output increases, it means that the heart is pumping more blood per minute. To maintain a constant arterial blood pressure, the peripheral resistance needs to decrease to allow for easier blood flow through the blood vessels. This can be illustrated by the equation: Blood Pressure = Cardiac Output x Peripheral Resistance.
For example, let's say the cardiac output increases due to increased heart rate or stroke volume. If the peripheral resistance remains the same, the blood pressure would increase because there is more blood being pumped into the system with the same amount of resistance. To maintain a constant blood pressure, the peripheral resistance needs to decrease to offset the increased cardiac output.