Parasympathetic+Nervous+System

=**The Parasympathetic Nervous System.**=

The Parasympathetic Nervous system controls the slowing down of heart rate,  conserves energy as it slows the heart rate,  the increase of intestinal and glandular activity, and the relaxation of the sphincter musicales in the gastrointestinal tract.  This nervous system, unlike the Sympathetic Nervous system, does not necessarily use all of these functions at once, but selects the ones that are needed at that given time. It is also responsible for the body’s’ ability to recuperate and return to a balanced state after experiencing pain or stress. It is also constantly active at a lower level, but levels of activity increase when it is necessary to bring it back to its natural state. The Parasympathetic nervous system often refers to being the “relax and renew” system, while the Sympathetic Nervous system is referred to “fight or flight”. The main or primary nerve is called the Vaugs nerve, or also known as Cranial Nerve X. The Parasympathetic Nervous system is a branch off of the Autonomic Nervous system which is the part of your nervous system that controls involuntary actions, such as the beating of your heart, and the winding or narrowing of the blood vessels. To stimulate the Parasympathetic nerves, some use Physostigmine. Physostigmine is a reversible anticnollnesterase drug used as a parasympathetic, which when used in the eye constricts the pupil. It has been used for the treatment of glaucoma, but due to its side effects, its usage is rare and it has been discontinued.  Parasympathetics are autonomic or visceral branches of the peripheral nervous system . Parasympathetic nerve fibers arise from the  center of the nervous system with the S2, S3, and S4 spinal nerves and from the third, seventh, ninth, and tenth cranial nerves. The parasympathetic nervous system uses chiefly acetylcholine (ACh) as its neurotransmitter even though peptides , such as cholecystokinin, may act on the PSNS as a neurotransmitter.The ACh acts on two types of receptors, the muscarinic and nicotinic cholinergic receptors. Most transmissions occur in two stages: When stimulated, the preganglionic nerve releases ACh at the ganglion, which acts on nicotinic receptors of postganglionic neurons. The postganglionic nerve then releases ACh to stimulate the muscarinic receptors of the target organ.

The differences between Parasympathetic and Sympathetic organs. __**REFERENCES**__ [|Science Daily] [|Parasympathetic and Sympathetic Nervous System] [|Side effects of Physostigmine]