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How do vasomotor nerves control the contraction and expansion of blood vessels?
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Physiology
Adenosine triphosphate (ATP) is the power source of many biochemical reactions. It is produced in the cell structures and system listed at the left to energize the important life processes listed on the right. An abbreviated chemical formula of the structure of ATP is also shown. The two high-energy P―O―P bonds are responsible for its power.
The contraction and expansion of blood vessels are primarily regulated by the autonomic nervous system, which utilizes chemical signaling to modulate the diameter of these vessels.12
Mechanisms of Control
The sympathetic nervous system plays a central role in controlling vasomotor tone through the release of neurotransmitters, most notably norepinephrine.32
- Vasoconstriction: When sympathetic fibers are stimulated, they release norepinephrine, which binds to -adrenergic receptors on the smooth muscle of blood vessels. This binding initiates biochemical reactions that cause the vessels to narrow, thereby increasing blood pressure. Some neurons also release neuropeptide Y alongside norepinephrine to modulate this response.32
- Vasodilation: While the sympathetic system is often associated with constriction, the body also employs vasodilators to widen vessels, which helps regulate body temperature and blood pressure. This process can involve various signaling molecules, including nitric oxide, which acts as a messenger to relax vascular smooth muscle.42
Because autonomic nerve terminals often have large gaps between themselves and their effector cells, these neurotransmitters act on specific receptors to produce either short-term or long-lasting physiological changes, allowing the body to adapt to stress or environmental conditions.2