Tick the substances whose mechanisms are based on interaction with ion channels

Correct Answer: D

Rationale: The correct answer is D because all the substances listed interact with ion channels. Sodium channel blockers inhibit sodium influx, calcium channel blockers block calcium entry, and potassium channel activators enhance potassium efflux. A and B specifically target ion channels, while C indirectly influences ion channels through potassium activation. Therefore, all choices align with ion channel interactions.

Correct Answer: B

Rationale: Rationale: 1. Atropine is a muscarinic receptor antagonist. 2. It competes with pilocarpine and choline esters for the muscarinic receptors. 3. By binding to the receptors, atropine blocks the excessive stimulation. Summary: - A: Edrophonium is an acetylcholinesterase inhibitor, not a muscarinic receptor antagonist. - C: Pralidoxime is used to treat organophosphate poisoning, not muscarinic receptor overstimulation. - D: Echothiophate is a long-acting acetylcholinesterase inhibitor, not a muscarinic receptor antagonist.

Correct Answer: D

Rationale: Succinylcholine is the correct answer because it is a depolarizing agent with an extremely brief duration of action. It rapidly metabolizes by plasma cholinesterase, leading to a short duration of effect. Mivacurium, Rocuronium, and Rapacuronium are non-depolarizing agents with longer durations of action due to their mechanisms of action and metabolism, making them incorrect choices.

Correct Answer: B

Rationale: The correct answer is B because methoxamine is a direct-acting alpha1-receptor agonist that increases blood pressure by causing vasoconstriction and increasing total peripheral resistance. It does not increase heart rate, contractility, or cardiac output; instead, it can cause reflex bradycardia due to its hypertensive effect. Therefore, the statement that it increases heart rate, contractility, and cardiac output is incorrect. The other choices (A, C, and D) are all characteristics of methoxamine, making them incorrect options for this question.

Correct Answer: B

Rationale: The correct answer is B. Beta-receptor antagonists, also known as beta-blockers, do not cause a fall in peripheral resistance as an acute effect. Here's why: A, negative inotropic and chronotropic effects, occur because beta-blockers decrease heart rate and contractility. C, vasoconstriction, is not a direct effect of beta-blockers; they actually cause vasodilation. D, reduction of renin release, is correct as beta-blockers inhibit renin-angiotensin system activity. Therefore, B is the exception among the listed cardiovascular effects of beta-receptor antagonists.