Final answer:
ANP leads to a decrease in total blood volume and a decrease in systemic blood pressure by causing vasodilation and promoting the excretion of sodium and water.
Step-by-step explanation:
The correct answer to the question regarding systemic blood vessels responding to atrial natriuretic peptide (ANP) is: (B) Decrease in total blood volume and increased systemic pressure. However, an accurate understanding of ANP's function suggests a slight adjustment to this answer is necessary: ANP actually leads to blood vessel dilation, resulting in a decrease in blood volume and a decrease in systemic pressure.
ANP is released by cells in the atrium of the heart in response to an increase in blood volume. Consequently, ANP causes the kidneys to reduce sodium reabsorption, which in turn decreases blood volume as both sodium and water are excreted. Additionally, ANP leads to vasodilation, which lowers systemic blood pressure. The release of aldosterone and renin is also suppressed by ANP, contributing further to the reduction in blood volume and pressure.