Sympathetic control of smooth muscle

The sympathetic nervous system is the part of the autonomic nervous system that prepares the body to react to stress or emergency situations. It is mainly formed by adrenergic fibers and tends to decrease the tone and contractility of smooth muscle.

It consists of preganglionic and postganglionic fibers, both connected in the ganglia. The preganglionic fibers are short, while the postganglionic ones are long.

Figure 1: Schematic representation of smooth muscle sympathetic control. Two different neurotransmitters are released in the sympathetic nervous system: acetylcholine (ACh) from the preganglionic fiber and Norepinephrine (NE) from the postganglionic fiber to the end organ. ACh binds to nicotinic receptors in the postganglionic fiber, while the NE binds to adrenergic receptors in the end tissue.