How does the acetylcholine affect the blood vessels?

ACH effect on BV: M3 muscarinic ach receptors are located in smooth muscles of blood vessels. Because they're gq-coupled & mediate increase in intracellular calcium, they typically cause contraction of smooth muscle (as in bronchi). But activation of m3 on vascular endothelial cells causes increased synthesis of nitric oxide, which diffuses to adjacent vascular smooth muscle cells and causes their relaxation.