Cross references:   Acetylcholine Gate     Acetylcholine Metabotropic Receptor   
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Acetylcholine (Wiki)   

    "The chemical compound acetylcholine (often abbreviated ACh) is a neurotransmitter in both the peripheral nervous system (PNS) and central nervous system (CNS) in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system (ANS) and the only neurotransmitter used in the motor division of the Somatic Nervous System (sensory neurons use glutamate and various peptides at their synapses). Acetylcholine is also the principal neurotransmitter in all autonomic ganglia.
    Acetylcholine slows the heart rate when functioning as an inhibitory neurotransmitter. However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions.[1]


Acetylcholine and the associated neurons form a neurotransmitter system, the cholinergic system from the brainstem and basal forebrain that projects axons to many areas of the brain. In the brainstem it originates from the Pedunculopontine nucleus and dorsolateral tegmental nuclei collectively known as the mesopontine tegmentum area or pontomesencephalotegmental complex.[6][7] In the basal forebrain, it originates from the basal optic nucleus of Meynert and medial septal nucleus:     In addition, ACh acts as an important "internal" transmitter in the striatum, which is part of the basal ganglia. It is released by a large set of interneurons with smooth dendrites, known as tonically active neurons or TANs."  

Acetylcholine - Wikipedia   
Acetylcholine is an organic chemical that functions in the brain and body of many types of animals, including humans, as a neurotransmitter—a chemical released by nerve cells to send signals to other cells. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Parts in the body that use or are affected by acetylcholine are referred to as cholinergic. Substances that interfere with acetylcholine activity are called anticholinergics.

Acetylcholine is the neurotransmitter used at the neuromuscular junction—in other words, it is the chemical that motor neurons of the nervous system release in order to activate muscles. This property means that drugs that affect cholinergic systems can have very dangerous effects ranging from paralysis to convulsions. Acetylcholine is also used as a neurotransmitter in the autonomic nervous system, both as an internal transmitter for the sympathetic nervous system and as the final product released by the parasympathetic nervous system.

In the brain, acetylcholine functions as a neurotransmitter and as a neuromodulator. The brain contains a number of cholinergic areas, each with distinct functions. They play an important role in arousal, attention, memory and motivation.

Partly because of its muscle-activating function, but also because of its functions in the autonomic nervous system and brain, a large number of important drugs exert their effects by altering cholinergic transmission. Numerous venoms and toxins produced by plants, animals, and bacteria, as well as chemical nerve agents such as Sarin, cause harm by inactivating or hyperactivating muscles via their influences on the neuromuscular junction. Drugs that act on muscarinic acetylcholine receptors, such as atropine, can be poisonous in large quantities, but in smaller doses they are commonly used to treat certain heart conditions and eye problems. Scopolamine, which acts mainly on muscarinic receptors in the brain, can cause delirium and amnesia. The addictive qualities of nicotine derive from its effects on nicotinic acetylcholine receptors in the brain.