Inhaled anesthetics and intravenous agents having general anesthetic properties:

Correct Answer: A

Rationale: Rationale: Inhaled anesthetics and intravenous agents with general anesthetic properties directly activate GABAA receptors. GABAA receptors are inhibitory neurotransmitter receptors in the brain. Activation of GABAA receptors leads to hyperpolarization of the neuron, resulting in decreased neuronal excitability and ultimately producing the anesthetic effect. Summary: A: Direct activation of GABAA receptors is correct as it aligns with the mechanism of action of general anesthetics. B: Facilitating GABA action but not directly acting on GABAA receptors is incorrect as direct activation is necessary for the anesthetic effect. C: Reducing glutamatergic neurotransmission is incorrect as it is not the primary mechanism of action for general anesthetics. D: Increasing the duration of opening of nicotine-activated potassium channels is incorrect as it is not related to the mechanism of action of general anesthetics.

Correct Answer: C

Rationale: The correct answer is C: Activation of the antifibrinolytic system. This system is involved in clot dissolution, not bleeding control. Platelet adhesion, release, and triggering the coagulation process are essential physiological reactions that help control bleeding by forming a stable blood clot. Platelet adhesion allows platelets to stick to the site of injury, platelet release releases factors that promote clot formation, and triggering the coagulation process leads to the formation of fibrin strands that strengthen the clot. Therefore, choices A, B, and D are involved in the control of bleeding, while choice C is not.

Correct Answer: A

Rationale: Step 1: Class IC antiarrhythmic drugs work by blocking sodium channels to slow down conduction in the heart. Step 2: Flecainide is a Class IC antiarrhythmic drug that specifically blocks sodium channels effectively. Step 3: Sotalol (Choice B) is a Class III antiarrhythmic drug that blocks potassium channels. Step 4: Lidocaine (Choice C) is a Class IB antiarrhythmic drug that also blocks sodium channels, but it is not a Class IC drug. Step 5: Verapamil (Choice D) is a calcium channel blocker and not a Class IC antiarrhythmic drug. Summary: Flecainide (Choice A) is the correct answer as it is a Class IC antiarrhythmic drug that blocks sodium channels, while the other choices are different classes of antiarrhythmics with different mechanisms of action.

Correct Answer: C

Rationale: The correct answer is C: Guanethidine. Guanethidine is a sympatholytic drug that blocks the release of norepinephrine from sympathetic nerve terminals, thus reducing sympathetic activity. This leads to a decrease in blood pressure. A: Labetalol is a non-selective beta blocker with alpha-blocking activity. B: Prazosin is an alpha-1 adrenergic receptor antagonist. D: Clonidine is a centrally acting alpha-2 adrenergic agonist. Therefore, the correct choice for a sympatholytic drug is Guanethidine due to its mechanism of action in inhibiting sympathetic activity.

Correct Answer: C

Rationale: The correct answer is C: Dysfunction of regulation of cerebral vessel tonus. Migraine is a neurological disorder characterized by recurrent headaches. The underlying cause is believed to involve abnormal brain activity and the dysfunction of regulating cerebral vessel tonus, leading to vasodilation and inflammation. Thrombosis of cerebral vessels (choice A), brain hemorrhage (choice B), and malignant growth in the brain (choice D) are not directly associated with the pathophysiology of migraine.