Final answer:
Nitric oxide is synthesized on demand and is known for causing vasodilation. It works by diffusing across cell membranes and binding to intracellular receptors in smooth muscle cells, triggering their relaxation and the expansion of blood vessels.
Step-by-step explanation:
Nitric oxide (NO) is not stored in nerve terminals and vascular endothelial cells; rather it is synthesized on demand and acts immediately due to its short-lived nature.
Among the three paracrine chemicals mentioned—ATP, adenosine, and nitric oxide—it is nitric oxide that is known for causing vasodilation. Nitric oxide diffuses across the plasma membrane of cells, interacts with receptors in smooth muscle cells, and leads to their relaxation, thereby causing vasodilation, an expansion of the blood vessels. This process restores blood flow and is crucial in situations such as heart disease treatment via nitroglycerin and in the mechanism of action of medications for erectile dysfunction like Viagra.
Nitric oxide functions as a signaling molecule and induces vasodilation by binding to intracellular receptors rather than G-protein-linked receptors, receptor tyrosine kinases, or gated ion channels. As a gas, it diffuses easily and acts locally given its short half-life.