Autonomic nervous system - parasympathetic nervous system (English)

The origin of the parasympathetic nervous system is found within the medulla oblongata and the sacral spinal cord. Like the sympathetic pathway, the parasympathetic pathway also consists of two neurons, the preganglionic (presynaptic) and postganglionic (postsynaptic) neurons, and parasympathetic ganglia. The presynaptic neurons of the parasympathetic system are located within the medulla oblongata and sacral spinal cord (S2-S4). These neurons send preganglionic fibers that synapse with the parasympathetic ganglia. In contrast to sympathetic ganglia, the parasympathetic ganglia are found near or within their target organs, which is why the parasympathetic preganglionic fibers are much longer than the sympathetic preganglionic fibers. The preganglionic fibers synapse with the postsynaptic neurons within the parasympathetic ganglia, which in turn project short postganglionic fibers to target organs, releasing the neurotransmitter acetylcholine.