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Welcome to 2 minute neuroscience, where I explain neuroscience topics in 2 minutes or
less.
In this installment I will discuss acetylcholine.
Acetylcholine was the first neurotransmitter discovered, and is named for the two substances
used to synthesize it: the nutrient choline and the enzyme acetyl coenzyme A.
Neurons that contain acetylcholine are called cholinergic.
There are several clusters of cholinergic neurons throughout the brain.
Some are found in the basal forebrain; they include the medial septal nucleus, the nucleus
of the diagonal band, and the nucleus basalis.
Others are found in the brainstem, including the pedunculopontine nucleus and laterodorsal
tegmental nucleus.
Acetylcholine acts on two families of receptors, and each receptor family has several subtypes.
One family is ionotropic; they are called nicotinic acetylcholine receptors because
nicotine also binds to and activates the receptors.
Their activation generally results in excitation of the neuron.
Another family is metabotropic.
These are called muscarinic acetylcholine receptors because a substance called muscarine
binds to them; their effects depend on the subtype of the receptor.
The action of acetylcholine in the synapse is terminated by an enzyme called acetylcholinesterase,
which breaks acetylcholine down into acetate and choline.
The choline is then transported back into neurons to synthesize more acetylcholine.
Acetylcholine has a variety of functions in the nervous system.
It is the main neurotransmitter used at neuromuscular junctions, and is responsible for muscle contraction.
It is also widely used in the autonomic nervous system.
Its functions in the brain are still not fully understood, but it does appear to play important
roles in memory, arousal, and attention.