Final answer:
When preload is too high, the baroreceptors stimulate parasympathetic activity, resulting in a lower heart rate and cardiac output, and causing a decrease in blood pressure, not an increase.
Step-by-step explanation:
When the preload is too high, the body activates various mechanisms to reduce the strain on the heart and lower blood pressure. High preload refers to the increased volume of blood in the ventricles before they contract, putting more strain on the heart. The body's response to high preload involves the activation of baroreceptors, which are sensitive to changes in blood pressure. When blood pressure rises too high, baroreceptors increase their firing rate, which results in parasympathetic stimulation of the heart. This stimulation ultimately leads to a decrease in cardiac output because the heart rate decreases, and may result in vasodilation of peripheral arterioles due to decreased sympathetic tone. Consequently, the blood pressure decreases rather than increases. Therefore, when preload is too high, the blood pressure decreases (option 3), not increases.