All of the following are neurotransmitters EXCEPT?

AIIMS Raipur - 2017 (Shift-3)

Applied Physiology

Easy

Appeared in: AIIMS Raipur - 2017 (Shift-3)

Explanation

Troponin is a complex of regulatory proteins found in the sarcomeres of striated muscle (skeletal and cardiac).
It is not a chemical messenger that transmits signals between neurons; its function is to regulate muscle contraction.
When a muscle cell is stimulated, calcium ions bind to troponin, which causes a conformational change in the troponin-tropomyosin complex, exposing binding sites on the actin filament and allowing muscle contraction to occur.
Clinically, cardiac-specific troponins (cTnI and cTnT) are measured in the blood as sensitive and specific markers of myocardial injury (heart attack).

Option A: Dopamine is a well-known neurotransmitter belonging to the catecholamine family.
Option B: GABA (Gamma-aminobutyric acid) is the primary inhibitory neurotransmitter in the central nervous system.
Option C: Serotonin (5-hydroxytryptamine or 5-HT) is a key neurotransmitter that plays a major role in regulating mood, sleep, and appetite.

Visual 1: Diagram - A labeled diagram of a chemical synapse, showing the presynaptic terminal releasing neurotransmitters (like dopamine, GABA, serotonin) into the synaptic cleft to bind with receptors on the postsynaptic neuron.
Visual 2: Diagram - An illustration of a muscle sarcomere, highlighting the troponin complex on the actin filament and its interaction with calcium and tropomyosin during muscle contraction.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Differentiating neurotransmitters from other biomolecules, specifically muscle proteins as background academic context rather than a clinical decision trigger.
Understanding the difference between neurotransmitters and other biomarkers is critical for interpreting lab results and understanding pathophysiology. A high troponin level points to cardiac damage, not a neurological disorder.
Many psychiatric and neurological medications work by modulating neurotransmitter systems (e.g., SSRIs for serotonin, antipsychotics for dopamine). Nurses must understand this to monitor for therapeutic effects and side effects.
What if? If a patient with chest pain has normal troponin levels but shows signs of confusion and agitation, the nurse's focus should shift from an acute cardiac event to investigating other causes, which could be neurological (e.g., stroke, delirium) or metabolic, possibly involving neurotransmitter imbalances.

How to Approach the Question

First, identify the core concept of the question, which is 'neurotransmitters'.
Note the keyword 'EXCEPT'. This means you are looking for the option that does not fit the category of a neurotransmitter.
Review each option: Dopamine, GABA, and Serotonin are all well-known neurotransmitters involved in various functions of the nervous system.
Consider the last option, Troponin. Recall or deduce its function. Troponin is associated with muscle, specifically cardiac muscle, and is a key lab marker for heart attacks.
Since Troponin is a muscle protein and not a chemical messenger for neurons, it is the correct answer as the exception.

Concept Tested & Keywords

Concept Tested: Differentiating neurotransmitters from other biomolecules, specifically muscle proteins.
Stem keywords: neurotransmitters
Lead-in keywords: EXCEPT
Negative lead-in flag: This is a negative-lead-in question requiring you to identify the option that does not belong to the specified category.

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