Discovery and Functions of Acetylcholine

Acetylcholine (ACh) is one of the most abundantneurotransmittersin the human body. It is found in both thecentral nervous system(CNS) and theperipheral nervous system(PNS).

The name acetylcholine is derived from its structure. It is a chemical compound made up of acetic acid and choline. Cholinergic synapses are those in which transmission is mediated by acetylcholine.

Why It's Important

Why is acetylcholine so important in the body? It serves a number of critical functions, many of which can be impaired by diseases or drugs that influence the function of this neurotransmitter.

Acetylcholine can be found in all motor neurons, where it stimulates muscles to contract. From the movements of the stomach and heart to the blink of an eyelash, all of the body's movements involve the actions of this important neurotransmitter.

It is also found in many brain neurons and plays an important role in mental processes such as memory and cognition. Severe depletion of acetylcholine is associated with Alzheimer's disease.

Discovery

Acetylcholine is not only the most common chemical messenger, but it was also the very first neurotransmitter to be identified. It was discovered by Henry Hallett Dale in 1914, and its existence was later confirmed by Otto Loewi. Both individuals were awarded the Nobel Prize in Physiology/Medicine in 1936 for their discovery.

Function in the Body

Acetylcholine has numerous functions in the body.

Muscles

In the peripheral nervous system, acetylcholine is a major part of thesomatic nervous system. Within this system, it plays an excitatory role leading to the activation of muscles.

Within the autonomic system, acetylcholine controls a number of functions by acting on preganglionic neurons in thesympatheticand parasympathetic systems. It is also the neurotransmitter released at all parasympathetic innervated organs, promoting contraction of smooth muscles, dilation of blood vessels, increased body secretions, and a slower heart rate.

For example, the brain might send out a signal to move the right arm. The signal is carried by nerve fibers to the neuromuscular junctions. The signal is transmitted across this junction by the acetylcholine neurotransmitter, triggering the desired response in those specific muscles.

Brain and Central Nervous System

Acetylcholine also acts at various sites within the central nervous system where it can function as a neurotransmitter and as a neuromodulator. It plays a role in motivation, arousal, attention, learning, and memory, and is also involved in promotingREM sleep.

Critical cholinergic pathway deterioration in the CNS has been associated with the onset of Alzheimer's disease. Drugs and substances that interrupt acetylcholine function can have negative effects on the body and can even lead to death. Examples of such substances include some types of pesticides and nerve gasses.

A Word From Verywell

Acetylcholine is a critical neurotransmitter that plays an important role in the normal function of the brain and body. Disruptions in the release and function of this neurotransmitter can result in significant problems in areas such as memory and movement.