Final answer:
During exercise, the body communicates with the brain about blood via neural, endocrine, and autoregulatory pathways to adjust blood flow and pressure according to the demands of physical activity.
Step-by-step explanation:
The body communicates with the brain about blood during exercise through three main pathways: neural, endocrine, and autoregulatory mechanisms. Neural mechanisms involve the cardiovascular centers in the medulla oblongata, baroreceptors, and chemoreceptors that monitor blood oxygen, carbon dioxide, and hydrogen ion levels. The endocrine system communicates changes via hormones such as epinephrine, norepinephrine, ADH, and others that affect blood flow and pressure. Autoregulation involves local control of blood vessels through chemical signals and the myogenic response to ensure proper blood distribution to active tissues during exercise.