How Acetylcholine Functions in Your Body

What Is Acetylcholine and Why Is It Important?

Acetylcholine (ACh) is a chemical that plays an important role in many different body functions. It is a neurotransmitter, and its main role is to communicate 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.

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.

Acetylcholine is also found in many brain neurons where it plays a vital role in mental processes and human behaviors, such as memory and cognition. It is involved in attention, arousal, neuroplasticity, and REM sleep.

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.

The 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 block or interrupt acetylcholine function, such as some types of pesticides and nerve gasses, can have negative effects on the body and may even lead to death.

Choline and Acetylcholine

Acetylcholine production takes place in the nerve terminals of cholinergic neurons. It is made by the choline acetyltransferase enzyme.

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

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.

Some of these conditions involve the depletion of acetylcholine or damage to acetylcholine receptors, but excessive acetylcholine can also have damaging effects. When acetylcholine increases in the synapses and neuromuscular joints, it can lead to what is known as nicotinic and muscarinic toxicity. Symptoms include increased salivation, cramps, diarrhea, blurry vision, paralysis, and muscle twitches.

Alzheimer's Disease

Alzheimer's disease causes problems with memory and thinking. It is an example of a condition that may be caused by acetylcholine deficiency. The exact causes of the condition are unknown, but the disease affects 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.

Medications That Affect Acetylcholine

Medications that affect acetylcholine are used to treat certain health conditions.

• Botox is a medication that interferes with acetylcholine in specific muscles where it is injected. It leads to paralysis of those muscles, which is why it temporarily reduces wrinkles.
• AChE (acetylcholinesterase) inhibitors are medications that affect the enzymes that are used in acetylcholine production. These medications, which include Aricept (donepezil), Exelon (rivastigmine), and Razadyne (galantamine), are used to help improve symptoms of Alzheimer's disease and myasthenia gravis.
• Anticholinergics are medications that block the actions of acetylcholine. These medications are often used to treat Parkinson's disease.