Question

Which of the following neurotransmitters is NOT classified as a catecholamine? (A) Epinephrine (B) Norepinephrine (C) Dopamine (D)Acetylcholine

Short answer

D) Acetylcholine

Step-by-step solution

- Understand Catecholamines

Catecholamines are a class of neurotransmitters that are derived from the amino acid tyrosine. The main catecholamines include epinephrine, norepinephrine, and dopamine.

- Identify Catecholamines from Options

Examine each option to see if it is classified as a catecholamine. Epinephrine (A), norepinephrine (B), and dopamine (C) are all catecholamines.

- Identify the Non-Catecholamine

The only option left is acetylcholine (D). Acetylcholine is classified as a different type of neurotransmitter and is not a catecholamine.

Key concepts

catecholamines

Catecholamines are a class of neurotransmitters that play a major role in the body's response to stress. They are derived from the amino acid tyrosine.
The three main catecholamines include:

• Epinephrine: Also known as adrenaline, it's crucial for the 'fight or flight' response, causing an increase in heart rate and blood pressure.
• Norepinephrine: Similar to epinephrine, it's involved in arousal and alertness.
• Dopamine: This neurotransmitter is integral for reward and pleasure systems in the brain, along with motor control.

These catecholamines are synthesized in the adrenal medulla and the brain.
They are essential for various physiological responses and are released during stress.

acetylcholine

Acetylcholine is a different type of neurotransmitter, distinct from the catecholamines. It is derived from the compounds choline and acetyl-CoA.
It plays several vital roles in the body:

• Motor Control: Found in neuromuscular junctions, it is responsible for stimulating muscle contractions.
• Memory and Learning: In the brain, acetylcholine is essential for cognitive functions including memory and learning.
• Autonomic Nervous System: It also influences various functions of the autonomic nervous system, such as slowing the heart rate.

Acetylcholine is broken down by the enzyme acetylcholinesterase, making it different from catecholamines that are typically broken down by monoamine oxidase.

amino acids

Amino acids are organic compounds that play a key role in neurotransmitter synthesis. Tyrosine, for instance, is a precursor for catecholamines.
Neurotransmitters derived from amino acids include:

• Glutamate: The most common excitatory neurotransmitter in the brain, essential for synaptic plasticity.
• GABA (Gamma-Aminobutyric Acid): The main inhibitory neurotransmitter in the brain, important for reducing neuronal excitability.
• Glycine: Functions as an inhibitory neurotransmitter in the spinal cord.

These amino acid-derived neurotransmitters affect various functions such as mood, arousal, and motor control.
Understanding these neurotransmitters helps in grasping how the nervous system regulates numerous physiological processes.