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Which neurotransmitter has both muscarinic and nicotinic receptor subtypes?

A.

Serotonin

B.

Acetylcholine

C.

Dopamine

D.

Gamma-aminobutyric acid (GABA)

Answer and Explanation

The Correct Answer is B

Choice A reason: Serotonin acts on 5-HT receptors, not muscarinic or nicotinic subtypes. It modulates mood and behavior but lacks the receptor diversity of acetylcholine. Serotonin’s receptors are G-protein-coupled or ligand-gated, unrelated to muscarinic or nicotinic mechanisms, making it incorrect for this neurotransmitter classification.

Choice B reason: Acetylcholine binds to muscarinic (G-protein-coupled) and nicotinic (ligand-gated) receptors. Muscarinic receptors regulate parasympathetic functions like heart rate, while nicotinic receptors mediate muscle contraction and CNS signaling. This dual receptor system is unique to acetylcholine, making it the correct neurotransmitter for this question.

Choice C reason: Dopamine acts on D1 and D2 receptors, not muscarinic or nicotinic subtypes. It regulates reward and motor functions but lacks the cholinergic receptor classifications. Dopamine’s receptors are G-protein-coupled, not ligand-gated like nicotinic, making it an incorrect choice for this neurotransmitter property.

Choice D reason: GABA binds to GABA-A (ligand-gated) and GABA-B (G-protein-coupled) receptors, not muscarinic or nicotinic. It inhibits neural activity, unrelated to cholinergic systems. GABA’s receptors mediate inhibitory signaling, not the excitatory or parasympathetic functions of muscarinic/nicotinic receptors, rendering it incorrect for this question.


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Related Questions

Correct Answer is B

Explanation

Choice A reason: Intervening in self-harm prioritizes beneficence, ensuring safety, over autonomy. Self-mutilation, often linked to dysregulated serotonin or impulsivity, requires immediate action to prevent harm, overriding patient choice. Autonomy is secondary when safety is at risk, making this an incorrect application of the principle.

Choice B reason: Exploring medication options respects autonomy by involving patients in decisions, aligning with their values. This considers individual neurobiological responses (e.g., serotonin reuptake variations) and preferences, empowering informed choice. Autonomy emphasizes patient control over treatment, making this the correct approach for ethical psychiatric care.

Choice C reason: Restricting patients for fighting prioritizes safety and unit order, not autonomy. Conflict may stem from emotional dysregulation or neurotransmitter imbalances, but restricting movement limits patient choice. This action reflects beneficence or justice, not autonomy, making it an incorrect choice for this ethical principle.

Choice D reason: Staying with an anxious patient supports emotional regulation, possibly linked to GABA deficits, but emphasizes beneficence over autonomy. While supportive, it does not involve patient decision-making. Autonomy requires empowering patient choice, not just presence, making this an incorrect application of the ethical principle.

Correct Answer is A

Explanation

Choice A reason: Blocking norepinephrine at alpha-1 receptors inhibits vasoconstriction, reducing vascular tone. This disrupts baroreceptor-mediated blood pressure regulation, causing orthostatic hypotension when standing. The autonomic nervous system fails to compensate for positional changes, leading to dizziness and fainting, a common side effect of alpha-1 blockers like prazosin.

Choice B reason: Increased psychotic symptoms are linked to dopamine dysregulation, not alpha-1 receptor blockade. Norepinephrine blockade affects autonomic functions, not psychosis, which involves mesolimbic dopamine hyperactivity. This side effect is unrelated to alpha-1 receptors, making this option scientifically inaccurate for the described mechanism.

Choice C reason: Appetite disturbance is typically associated with serotonin or histamine receptor effects, not alpha-1 norepinephrine blockade. Norepinephrine at alpha-1 receptors regulates vascular tone, not appetite control, which involves hypothalamic signaling. This side effect is not a direct consequence of alpha-1 blockade, rendering this option incorrect.

Choice D reason: Hypertensive crisis results from excessive norepinephrine activity, often due to monoamine oxidase inhibitors, not alpha-1 receptor blockade. Blocking alpha-1 receptors causes vasodilation, lowering blood pressure, not raising it. This makes hypertensive crisis an unlikely side effect, contrary to the pharmacological mechanism of alpha-1 blockers.

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