Neurotransmitters are chemical messengers that transmit signals between nerve cells (neurons) and other target cells, such as muscles, glands, or other neurons. They are released from synaptic vesicles in the axon terminals of a neuron into the synaptic cleft, where they bind to specific receptors on the postsynaptic cell to either excite or inhibit its activity. This chemical communication is essential for every brain and body function — from controlling movement, heart rate, and breathing, to regulating mood, sleep, memory, and behavior. Examples include dopamine (involved in motivation and reward), serotonin (mood and sleep regulation), GABA and glycine (inhibitory control), acetylcholine (muscle activation and memory), and norepinephrine and epinephrine (stress and alertness). Together, neurotransmitters form the foundation of how the nervous system processes information and coordinates complex physiological and psychological functions.
🧠 Neurotransmitter Quiz: Functions and Disorders
🧾 Answer Key — Neurotransmitter Quiz
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| b | b | c | d | b | a | c | b | d | a | c | a | d | b | c |
- Which of the following is the primary inhibitory neurotransmitter in the brain?
(a) Glutamate
(b) GABA
(c) Dopamine
(d) Acetylcholine - Which neurotransmitter is primarily associated with the “fight-or-flight” response?
(a) Serotonin
(b) Norepinephrine
(c) Glycine
(d) Endorphins - A deficiency of which neurotransmitter is most closely linked to Parkinson’s disease?
(a) Serotonin
(b) Acetylcholine
(c) Dopamine
(d) GABA - Which neurotransmitter is a key player in mood regulation, sleep, and appetite?
(a) Glutamate
(b) Dopamine
(c) Norepinephrine
(d) Serotonin - Which of the following is an amino acid that acts as an inhibitory neurotransmitter, particularly in the spinal cord?
(a) Glutamate
(b) Glycine
(c) Dopamine
(d) Epinephrine - Acetylcholine is the primary neurotransmitter at which junction?
(a) Neuromuscular junction
(b) NMDA receptor
(c) Serotonin pathway
(d) Nigrostriatal pathway - Which neurotransmitter is often referred to as the body’s natural painkiller?
(a) Acetylcholine
(b) Serotonin
(c) Endorphins
(d) Glycine
Neurotransmitter MCQ
- The brain’s reward and pleasure centers are primarily mediated by which neurotransmitter?
(a) GABA
(b) Dopamine
(c) Acetylcholine
(d) Norepinephrine - Which neurotransmitter is synthesized from the amino acid tryptophan?
(a) Dopamine
(b) Acetylcholine
(c) Norepinephrine
(d) Serotonin - Which of the following is a catecholamine neurotransmitter?
(a) Epinephrine
(b) GABA
(c) Glutamate
(d) Glycine
- Which neurotransmitter is crucial for the formation of new memories and synaptic plasticity?
(a) GABA
(b) Acetylcholine
(c) Glutamate
(d) Serotonin - A deficiency of which neurotransmitter is associated with Alzheimer’s disease?
(a) Acetylcholine
(b) Dopamine
(c) Serotonin
(d) Endorphins - Which neurotransmitter is an inhibitory neurotransmitter that helps regulate sleep and wakefulness?
(a) Serotonin
(b) Glutamate
(c) Norepinephrine
(d) GABA - Which neurotransmitter is synthesized from the amino acid tyrosine?
(a) Serotonin
(b) Dopamine
(c) Glycine
(d) Acetylcholine - Which of the following is a neuropeptide that acts as a neurotransmitter?
(a) Acetylcholine
(b) GABA
(c) Endorphin
(d) Nitric Oxide
🧾 Answer Key — Neurotransmitter Quiz
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| b | b | c | d | b | a | c | b | d | a | c | a | d | b | c |
Detailed Explanations of Neurotransmitter Quiz
1. Primary Inhibitory Neurotransmitter in the Brain Answer: (b) GABA
- Explanation: GABA (gamma-aminobutyric acid) is the chief inhibitory neurotransmitter in the mature mammalian central nervous system. Its primary role is to reduce neuronal excitability. It does this by binding to receptors, allowing negative ions to enter the neuron, which makes the cell resistant to firing. Drugs like benzodiazepines and barbiturates enhance the effect of GABA, leading to sedative, anxiolytic, and anticonvulsant effects.
2. Neurotransmitter Associated with “Fight-or-Flight”
- Answer: (b) Norepinephrine
- Explanation: Norepinephrine (also called noradrenaline) acts as both a hormone and a neurotransmitter. During a stress response, it is released widely, increasing arousal, alertness, and vigilance in the brain. In the body, it causes blood vessels to constrict, increases heart rate, and dilates airways, all of which prepare the body to face a threat.
3. Deficiency Linked to Parkinson’s Disease
- Answer: (c) Dopamine
- Explanation: Parkinson’s disease is a neurodegenerative disorder characterized by the progressive loss of dopamine-producing neurons in a key region of the midbrain. This dopamine deficit leads to the classic motor symptoms: resting tremor, muscle rigidity, and extreme slowness of movement. The primary treatment, Levodopa (L-DOPA), helps replenish the brain’s dwindling dopamine supply.
4. Key Player in Mood Regulation, Sleep, and Appetite
- Answer: (d) Serotonin
- Explanation: Serotonin is a monoamine neurotransmitter with widespread effects. It is heavily implicated in regulating mood and emotion, and its deficiency is a key factor in depression and anxiety disorders. It also plays a critical role in regulating sleep-wake cycles, appetite, pain perception, and gastrointestinal function. Many antidepressants work by increasing serotonin levels in the synaptic gap.
5. Inhibitory Amino Acid in the Spinal Cord
- Answer: (b) Glycine
- Explanation: Glycine is a simple amino acid that serves as a major inhibitory neurotransmitter, especially in the spinal cord, brainstem, and retina. Similar to GABA, it acts on receptors that lead to hyperpolarization and reduced firing of motor and sensory neurons. Strychnine, a potent poison, acts by blocking glycine receptors, leading to uncontrolled muscle spasms and convulsions.
Explanations Neurotransmitter MCQ
6. Acetylcholine’s Primary Junction
- Answer: (a) Neuromuscular junction
- Explanation: Acetylcholine (ACh) is the definitive neurotransmitter at the neuromuscular junction, the synapse between a motor neuron and a muscle fiber. When released, ACh binds to receptors on the muscle, triggering an electrical potential that leads to muscle contraction. It is also critical in the CNS for attention, learning, and memory.
7. The Body’s Natural Painkiller
- Answer: (c) Endorphins
- Explanation: Endorphins (a contraction of “endogenous morphine”) are neuropeptides produced by the central nervous system and the pituitary gland. They function by binding to opioid receptors in the brain and spinal cord. This binding inhibits the release of pain signals and activates reward pathways, leading to pain relief (analgesia) and feelings of euphoria, such as the “runner’s high.”
8. Brain’s Reward and Pleasure Centers
- Answer: (b) Dopamine
- Explanation: The dopamine system controls the central circuit of the brain’s reward system. Dopamine release in this pathway reinforces behaviors essential for survival (like eating) and is strongly linked to the subjective experience of pleasure and motivation. This system is often implicated in addiction.
9. Synthesized from Tryptophan
- Answer: (d) Serotonin
- Explanation: The biosynthesis of serotonin begins with the essential amino acid tryptophan, which is from diet from the diet. Tryptophan is chemically converted into serotonin (5-HT). This is why diet can influence serotonin levels; low tryptophan intake can lead to reduced serotonin synthesis.
10. A Catecholamine Neurotransmitter
- Answer: (a) Epinephrine
- Explanation: Catecholamines are a group of neurotransmitters and hormones that share a common chemical structure. They are all synthesized from the amino acid tyrosine. The three key catecholamines are Dopamine, Norepinephrine (synthesized from dopamine), and Epinephrine (synthesized from norepinephrine).
EXPLANATION
11. Crucial for New Memories and Synaptic Plasticity
Answer: (c) Glutamate
Explanation: Glutamate serves as the primary excitatory neurotransmitter in the brain, and moreover, it plays a key role in synaptic plasticity — the brain’s ability to strengthen or weaken synapses over time. In particular, the process known as Long-Term Potentiation (LTP), which represents the cellular basis of learning and memory, relies heavily on glutamate receptors. Therefore, glutamate is essential for forming new memories and learning processes.
12. Deficiency Associated with Alzheimer’s Disease
Answer: (a) Acetylcholine
Explanation: In Alzheimer’s disease, there is a profound loss of cholinergic neurons in the basal forebrain — the very neurons responsible for producing acetylcholine. As a result, this deficiency of acetylcholine leads to memory loss and cognitive decline. Furthermore, several Alzheimer’s medications work by inhibiting the enzyme acetylcholinesterase, which breaks down acetylcholine, thereby increasing its availability in the brain and temporarily improving symptoms.
13. Inhibitory Neurotransmitter Regulating Sleep and Wakefulness
Answer: (d) GABA
Explanation: GABA (Gamma-Aminobutyric Acid) acts as the main inhibitory neurotransmitter in the brain. More importantly, its widespread inhibitory action is essential for maintaining the balance between wakefulness and sleep. During the initiation of sleep, GABAergic neurons in specific brain regions become highly active and suppress arousal centers, effectively turning off the “wake state.” Consequently, many sleep aids and sedative drugs enhance GABA’s effect to promote relaxation and sleep.
14. Synthesized from Tyrosine
Answer: (b) Dopamine
Explanation: Dopamine is synthesized through the catecholamine biosynthetic pathway, which begins with the amino acid tyrosine. First, tyrosine is converted into L-DOPA, which is then transformed into dopamine. Moreover, dopamine itself serves as a precursor for two other important neurotransmitters — norepinephrine and epinephrine — thereby linking it directly to both motivation and stress-response mechanisms.
15. A Neuropeptide Neurotransmitter
Answer: (c) Endorphin
Explanation: Unlike classical small-molecule neurotransmitters such as GABA or glutamate, neuropeptides are composed of short chains of amino acids and act as both neurotransmitters and neuromodulators. Specifically, endorphins are a well-known group of neuropeptides that help reduce pain perception and enhance feelings of pleasure. In addition, they are synthesized in the neuronal cell body and then transported to the nerve terminal, making them functionally distinct from other neurotransmitters.