What Is Acetylcholine?

Acetylcholine molecule
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Acetylcholine (ACh) is is a chemical that plays an important role in many different body functions. It is a neurotransmitter that communicates signals between neurons in the central nervous system (CNS) and the peripheral nervous system (PNS).

Acetylcholine serves a number of critical functions, many of which can be impaired by diseases or drugs that influence the function of this neurotransmitter. The name acetylcholine is derived from its structure. It is a chemical compound made up of acetic acid and choline.

This article discusses how acetylcholine functions in the body as well as how it is produced. It also covers what can happen when acetylcholine function is impaired.

Acetylcholine Function

Acetylcholine has numerous functions in the body. It 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 eye, 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.

Some cells of the body have what are known as cholinergic synapses. These synapses convert an electrical signal into acetylcholine, which then interacts with acetylcholine receptors on the other side of the synapse to trigger another electrical signal.

Peripheral Nervous System

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

Within the autonomic system, acetylcholine controls a number of functions by acting on neurons in the ​sympathetic and parasympathetic systems. It is also involved in the contraction of smooth muscles and dilation of blood vessels, and it can promote 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 acetylcholine, triggering the desired response in those specific muscles.

Because acetylcholine plays an important role in muscle actions, drugs that influence this neurotransmitter can cause various degrees of movement disruption and even paralysis.

Brain and CNS

Acetylcholine also acts at various sites within the CNS, 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 promoting REM sleep.

Disrupted levels of acetylcholine may be associated with conditions such as Alzheimer's disease. Drugs and substances that interrupt acetylcholine function, such as some types of pesticides and nerve gasses, can have negative effects on the body and can even lead to death.

Discovery

Acetylcholine was the first neurotransmitter to be identified. It was discovered by Henry Hallett Dale in 1914, and its existence was later confirmed by Otto Loewi. Both were awarded the Nobel Prize in Physiology or Medicine in 1936 for their discovery.

Choline and Acetylcholine

Choline is a nutrient precursor of acetylcholine. The body uses choline to produce acetylcholine. When people don't consume enough choline, they may experience a range of negative health effects.

A lack of choline can affect the liver's ability to process fat, which increases the risk of liver cancer and diabetes. Children who lack choline in their diet during critical points of development may have impairments in mental function and cognitive performance as a result.

Because the body cannot produce enough choline on its own, it needs to be obtained from food. Supplements containing choline are available. Dietary sources of choline include:

  • Meat, fish, dairy, and eggs
  • Whole grains, legumes, nuts, and seeds
  • Broccoli, cabbage, apples, and tangerines

Adequate daily intake of choline is 550 mg per day for men and 425 mg per day for women over the age of 19 years old. Individuals who menstruate may need less because estrogen helps stimulate the synthesis of choline.

Acetylcholine Dysfunction

Acetylcholine's function in the body can be disrupted by a variety of causes, including disease and toxins. Imbalances in this important neurotransmitter can lead to a number of health consequences, many of which impact memory and muscle control.

Alzheimer's Disease

Alzheimer's disease causes problems with memory and thinking. The exact causes of the condition are not known, but the disease does affect acetylcholine, leading to low levels of the neurotransmitter.

Myasthenia Gravis

Myasthenia gravis is a condition that leads to muscle weakness. It can affect muscles in the arms, legs, neck, hands, and fingers. It is an autoimmune condition that occurs when the body's immune system attacks acetylcholine receptors. 

Parkinson's Disease

Parkinson's disease is a degenerative neurological condition that causes tremors and involuntary movements. While the exact causes of the condition are not fully understood, acetylcholine imbalances are believed to play a role.

Toxins and Pesticides

Certain toxins can affect acetylcholine in the body and enhance, mimic, or interact with acetylcholine. This can result in symptoms such as blurred vision, muscle weakness, diarrhea, and paralysis.

For example, the venom of a black widow spider interacts with acetylcholine. When a person is bitten by a black widow, their acetylcholine levels rise dramatically, leading to severe muscle contractions, spasms, paralysis, and even death.

Treatment for these conditions may involve taking medications, known as anticholinergics (ACE inhibitors) that work to block the actions of acetylcholine in the body.

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.

Frequently Asked Questions

  • What does acetylcholine do?

    Acetylcholine is a type of chemical messenger, or neurotransmitter, that plays a vital role in the central and peripheral nervous system. It is important for muscle control, autonomic body functions, and in learning, memory, and attention.

  • Where is acetylcholine produced?

    Certain cells known as cholinergic neurons produce acetylcholine by synthesizing it from choline and acetyl-coenzyme A (acetyl-CoA). This process takes place in the cytoplasm at the nerve terminals of the cell.

  • What is the role of acetylcholine in a muscle contraction?

    In order to contract a muscle, an electrical impulse must travel down a motor neuron until it arrives at the end of the cell. It then triggers the release of acetylcholine from tiny vesicles so that the neurotransmitter can cross the synaptic cleft and bind to receptors on the other side of the cell. The message can then trigger a response in the cell that it connects with.

  • What foods contain acetylcholine?

    The body produces acetylcholine by synthesizing it from choline. Good food sources of choline include meat, eggs, dairy, nuts, whole grains, apples, and broccoli.

13 Sources
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