What is the Difference Between Acetylcholine and Epinephrine

The main difference between acetylcholine and epinephrine is that acetylcholine is a neurotransmitter acting in the parasympathetic nervous system, whereas epinephrine is a hormone that stimulates the sympathetic nervous system.

Acetylcholine and epinephrine are two types of substances that can act as neurotransmitters. Generally, they involve in different types of functions in the nervous system.

Key Areas Covered

1. What is Acetylcholine
     – Definition, Features, Function
2. What is Epinephrine
     – Definition, Features, Function
3. What are the Similarities Between Acetylcholine and Epinephrine
     – Outline of Common Features
4.  What is the Difference Between Acetylcholine and Epinephrine
     – Comparison of Key Differences

Key Terms

Acetylcholine, Epinephrine

What is Acetylcholine

Acetylcholine is the chief neurotransmitter in the parasympathetic nervous system in the body. Also, it is a cholinergic neurotransmitter. Since this neurotransmitter acts on the parasympathetic nervous system, it slows the heart rate, increases the secretions like saliva, and increases blood flow. On the other hand, acetylcholine is an ester of choline and acetic acid. Here, the parasympathetic nervous system is a part of the autonomic nervous system. Cholinergic nerve ends secrete acetylcholine.

Figure 1: Acetylcholine

Furthermore, acetylcholine releases from the nerve ends of the peripheral nervous system when the nerve impulse arrives at the end of the motor neuron into the neuromuscular junction. Usually, the releasing neurotransmitters join with the receptors in the post-synaptic membrane. This generates a nerve impulse in the post-sympathetic neuron.

What is Epinephrine

Epinephrine or adrenaline is a hormone secreted by the medulla of adrenal glands. It is produced during strong emotions like fear or anger, giving a surge of energy to the body and released into the bloodstream in order to act on almost all the body tissues. Epinephrine is capable of constricting blood vessels in order to maintain blood pressure. It relaxes breathing tubes, allowing easier breathing as well. Eventually, epinephrine increases the heart rate, blood pressure, and sugar metabolism and muscle strength.

Figure 2: Epinephrine

Moreover, epinephrine stimulates alpha and beta receptors, but it is more effective on alpha receptors, which are involved in insulin secretion in the pancreas, glycogen breakdown in the liver and muscle, and glycolysis. Beta receptors are involved in glucagon secretion in the pancreas, increased ACTH secretion by the pituitary gland, and increased fat metabolism in adipose tissue.

Similarities Between Acetylcholine and Epinephrine

• Acetylcholine and epinephrine are two types of substances that act as neurotransmitters.
• Also, they have different functions in the nervous system.

Difference Between Acetylcholine and Epinephrine

Definition

Acetylcholine refers to a compound that occurs throughout the nervous system, in which it functions as a neurotransmitter while epinephrine refers to a hormone secreted by the adrenal glands that increases rates of blood circulation, breathing, and carbohydrate metabolism and prepares muscles for exertion.

Significance

Acetylcholine is the most abundant neurotransmitter in the nervous system while epinephrine is a neurotransmitter active outside the brain.

Type of Nervous System

Acetylcholine works in the parasympathetic nervous system while epinephrine works in the sympathetic nervous system.

Functions

Acetylcholine increases digestive blood flow, increases secretions like saliva, and slows the heart rate while epinephrine stimulates adrenergic receptors.

As a Hormone

Acetylcholine does not act as a hormone in the body while epinephrine acts as a hormone increasing the rates of blood circulation, breathing, and carbohydrate metabolism, and preparing the muscles for exertion.

Conclusion

In brief, acetylcholine and epinephrine are two types of substances that act as neurotransmitters. Generally, acetylcholine is the most abundant neurotransmitter in the body, acting in the parasympathetic nervous system. Also, the functions of acetylcholine include increasing the digestive blood flow, increasing secretions like saliva, and slowing the heart rate. Moreover, acetylcholine serves as a hormone to increase blood circulation, carbohydrate metabolism, etc. Meanwhile, epinephrine is another neurotransmitter that works outside the brain. However, it stimulates the sympathetic nervous system.  Therefore, the main difference between acetylcholine and epinephrine is their function.

References:

1. Acetylcholine (ACH): What it is, Function & Deficiency. Cleveland Clinic. (n.d.). Retrieved April 19, 2023
2. Epinephrine (adrenaline): What it is, function, deficiency & side effects. Cleveland Clinic. (n.d.). Retrieved April 19, 2023

Image Courtesy:

1. “Acetylcholin” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “Epinephrine” By Roland1952 – Own Work (Public Domain) via Commons Wikimedia