Final answer:
Increased blood volume leads to a decrease in sympathetic activity in the heart and vasodilation of renal arteries. This response helps regulate heart rate, cardiac output, and kidney filtration to maintain stable blood pressure and volume within the body.
Step-by-step explanation:
If blood volume increases, stretch receptors in the cardiovascular system respond by causing a decrease in sympathetic activity in the heart. This response serves as a reflex mechanism to lower blood pressure and reduce the risk of hypertension. The reduction in sympathetic activity leads to a decrease in heart rate and cardiac output. As a consequence of the decreased sympathetic activity, there is vasodilation of the renal arteries, which increases blood flow to the kidneys. This vasodilation is a part of an intricate regulatory mechanism to ensure the kidneys can properly filter blood at a healthy rate, maintaining homeostasis.
The kidneys are highly regulated by sympathetic nerves; under conditions of increased sympathetic stimulation, the kidneys experience vasoconstriction, which reduces the blood flow and filtration rate. Conversely, reduced sympathetic activity allows for the vasodilation of the afferent arterioles, leading to increased glomerular filtration rates. Essentially, the systemic adjustment to changes in blood volume and pressure is a coordinated effort that involves both the cardiovascular and renal systems to maintain blood pressure within a normal range.