 Dear students, in this topic we shall discuss the nervous control of microcirculation. First we shall discuss the role of nervous system in maintaining blood pressure. The arterial blood pressure is maintained by nervous system by adjusting the resistance to blood flow in peripheral circulation. And by controlling the number of capillaries open at any moment. If arterial blood pressure falls, nervous control of capillary flow ensures that blood flow to the brain and heart is maintained. And it also ensures that the blood flow to gut, liver and muscles is reduced. Because the more vital organs they have, the more blood they need to be transferred in such conditions when normal arterial blood pressure has fallen. Nervous control is possible because there are nervous innervations in the arterioles. The other three arterioles are innervated by sympathetic nerves. These sympathetic nerves release norepinephrine at their endings. Some arterioles are innervated by parasympathetic nerves which release acetylcholine at their endings. The sympathetic nerve stimulation in the arterioles causes the release of norepinephrine. Norepinephrine binds to alpha adeno receptors in smooth muscles of arterioles. This binding causes vasoconstriction that is decrease in the diameter of arterioles. Sympathetic nerves stimulation causes vasoconstriction and this vasoconstriction increases resistance to flow. So blood flow through capillary beds is reduced. Part of the microcirculation action of norepinephrine is modulated by another substance which is called neuropeptide y. Because of this norepinephrine and neuropeptide y action, blood flow decreases in coronary arteries. When parasympathetic nerves present in the arterioles are stimulated, acetylcholine is released. Parasympathetic nerves are present only in the arterioles of brain and lungs. When acetylcholine is produced, there is vasodilation in the arterioles which increases blood supply in the heart and lungs.