Parasympathische signalering

Parasympathetic signaling relays information from the nervous system to target organs, promoting rest, digestion, and relaxation responses. This pathway uses the neurotransmitter acetylcholine and its specific receptors, called cholinergic receptors.

There are two types of cholinergic receptors: nicotinic receptors in postganglionic fibers and muscarinic receptors in target tissues such as smooth muscles, cardiac muscles, and glands.

The parasympathetic signaling pathway begins when preganglionic neurons release acetylcholine. The released acetylcholine then binds and activates the nicotinic receptors on the postganglionic fibers.

The activated cells in postganglionic fibers release additional acetylcholine, subsequently stimulating the muscarinic receptors on the target tissue. Muscarinic receptors can either promote excitatory or inhibitory effects.

For instance, the activation of muscarinic receptors leads to the relaxation of the sphincter muscles in the gastrointestinal tract. This promotes the flow of food particles through the digestive system, aiding digestion.

In contrast, activation of muscarinic receptors in the smooth muscle lining of the bladder causes their activation and subsequent contraction. This contraction promotes urination.