Acetylcholine (Ach) was probably not the first neurotransmitter, but it was the first one to be identified. This occurred in 1915 through the work of Henry Hallett Dale, and it is very common in many locations throughout your body.
Ach is an interesting neurotransmitter because it is excitatory in some locations and inhibitory in others.
In the Peripheral Nervous System
Ach is the neurotransmitter that activates skeletal muscle. When your brain sends a signal to move your arm Ach is the messenger that transmits the message from the neuron to the muscle.
Acts on Your Heart
Acetylcholine also affects your heart muscle except on your heart it attaches to a different type of receptor where it causes a slowing or inhibition of your heart muscle contraction.
In Your Autonomic Nervous System
Your autonomic nervous system is composed of your sympathetic and parasympathetic nervous systems.
Acetylcholine is one of the major neurotransmitters these systems used to control your organs and other body parts without you thinking about.These autonomic reactions are known as your "fight or flight" and your "rest and digest" responses.
Within Your Brain
Ach is the neurotransmitter involved in many important functions of your brain. It has been shown to strengthen strong nerve signals and filter out weak signals coming into your brain.
The connections that it makes between parts of your brain play a part in the reward and arousal behaviors related to drug abuse, food intake, and sustaining attention.
This neurotransmitter that is found in so many different areas and has so many different effects accomplishes this by attaching to many different types of receptors. The stimulation of different types of receptors causes different types of responses.
On skeletal muscle it attaches to acetylcholine receptors.
On cardiac muscle it attaches to muscarinic receptors.
In the sympathetic nervous system it stimulates the release of epinephrine and norepinephrine.
Within the brain its effects, both excitatory and inhibitory, will vary depending on the site of release and the receptor subtypes available at that location.
Doctors can use medications to block certain receptors or to manipulate your Ach levels. They are attempting to cause specific reactions within your body.
Side effects and other problems can develop when other receptors are also blocked or the altered levels of Ach cause unintended reactions.
•Atropine blocks muscarinic receptors
This will cause dilation of your pupils, decreased stomach acid, and is also helpful in treating Parkinson's disease. It may also cause dry mouth, photophobia, and increased heart rate.
•Bethanechol mimics the action of Ach.
This will stimulate activity of the intestinal tract and is also helpful treating urinary retention. It may also cause nausea, vomiting, and sweating.
•Tacrine blocks Ach breakdown.
This medication is used to treat Alzheimer's disease. It may also cause confusion, seizures, and changes in behavior.
•Scopolamine blocks muscarinic receptors in your brain .
This helps to treat motion sickness, dizziness, and nausea. It may also cause blurred vision, sensitivity to light, and agitation.
•Physostigmine blocks Ach breakdown .
This treatment is used to diagnose and treat myasthenia gravis. It also lowers pressure within your eye and is used to treat glaucoma. It may also cause headaches, stomach pain, and anorexia.
Many of these medications can be very helpful for improving your life. However, whenever you start a new medicine you should discuss possible side effects with your doctor because any new treatment can have unintended consequences.
Ach is a neurotransmitter that is found throughout your body and it serves many different valuable functions. Researchers are working to find ways to manipulate or control it to help manage many different diseases.
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