Metabolic transformation (phase 1) is:

Correct Answer: B

Rationale: The correct answer is B because metabolic transformation (phase 1) involves the conversion of substances through oxidation, reduction, or hydrolysis processes, which alter the chemical structure of the compound. This phase prepares the substance for further metabolism or excretion. Acetylation and methylation (choice A) involve different enzymatic processes unrelated to phase 1 metabolism. Glucuronide formation (choice C) is part of phase 2 metabolism, not phase 1. Binding to plasma proteins (choice D) is not a metabolic transformation process but rather a mechanism of distribution in the body.

Correct Answer: C

Rationale: Muscarinic receptors are located in autonomic effector cells. These receptors respond to acetylcholine released by parasympathetic nerves in organs like the heart, smooth muscle, and glands. They play a key role in regulating functions such as heart rate, digestion, and glandular secretions. Autonomic ganglia (A) contain nicotinic receptors, not muscarinic. Skeletal muscle neuromuscular junctions (B) have nicotinic receptors. Sensory carotid sinus baroreceptor zone (D) is not directly involved in cholinergic signaling. Hence, the correct answer is C.

Correct Answer: A

Rationale: Atropine causes spasmolitic activity by blocking acetylcholine receptors, leading to relaxation of smooth muscles. This is beneficial in conditions like irritable bowel syndrome. Intestinal hypermotility, stimulation of gut contraction, and secretory activity are all effects opposite to what atropine causes due to its anticholinergic properties. Atropine's mechanism of action supports choice A as the correct answer.

Correct Answer: C

Rationale: The correct answer is C: Tachycardia. Direct beta1-adrenoreceptor stimulation leads to an increase in heart rate by enhancing the conduction of electrical impulses in the heart. Beta1 receptors are primarily located in the heart, particularly in the sinoatrial node, atria, and ventricles. This stimulation results in an increased rate of depolarization, leading to tachycardia. Choices A and B are incorrect because beta2 receptors are responsible for bronchodilation and vasodilation, respectively. Choice D is incorrect because bradycardia is not associated with direct beta1-adrenoreceptor stimulation.

Correct Answer: B

Rationale: The correct answer is B: Phentolamine. This drug is a nonselective alpha receptor antagonist, blocking both alpha-1 and alpha-2 receptors. It is used to treat hypertensive emergencies. Prazosin (A) is a selective alpha-1 receptor antagonist, used for hypertension and BPH. Metoprolol (C) is a beta blocker, mainly blocking beta-1 receptors for heart conditions. Reserpine (D) inhibits the uptake of norepinephrine into vesicles, reducing sympathetic activity.