All of the following parts of the heart are very sensitive to muscarinic receptor blockade except:

Correct Answer: D

Rationale: The correct answer is D: Ventricle. Muscarinic receptors are predominantly found in the atria, sinoatrial node, and atrioventricular node. Blocking these receptors can lead to decreased heart rate and conduction. The ventricles, however, are more sensitive to beta-adrenergic stimulation rather than muscarinic blockade. This is because beta-adrenergic receptors play a significant role in the contractility of the ventricles. Therefore, the ventricles are not as sensitive to muscarinic receptor blockade compared to the other parts of the heart.

Correct Answer: A

Rationale: The correct answer is A: Formoterol. It is a long-acting beta2-adrenergic agonist used in bronchial asthma therapy to dilate airways by relaxing smooth muscles. Norepinephrine (B) is a vasopressor, not used in asthma. Methoxamine (C) is an alpha1-adrenergic agonist, not indicated for asthma. Dobutamine (D) is a beta1-adrenergic agonist mainly used in heart failure, not asthma. Formoterol's mechanism of action aligns with the therapeutic goal of bronchial asthma treatment, making it the correct choice.

Correct Answer: C

Rationale: The correct answer is C: Pheochromocytoma. Beta-receptor blocking drugs are contraindicated in pheochromocytoma because they can potentially worsen hypertension due to unopposed alpha-adrenergic effects. Choice A is correct as beta-blockers are commonly used in hypertension, ischemic heart disease, and cardiac arrhythmias. Choice B is incorrect as beta-blockers are used in the treatment of glaucoma to reduce intraocular pressure. Choice D is incorrect as beta-blockers are used to manage symptoms of hyperthyroidism such as tachycardia and tremors.

Correct Answer: D

Rationale: The correct answer is D because all of the antiseizure drugs listed (Lamotrigine, Carbamazepin, Phenytoin) produce voltage-dependent inactivation of sodium channels. This mechanism helps to control neuronal excitability and prevent seizure activity. Lamotrigine inhibits voltage-gated sodium channels by stabilizing their inactive state. Carbamazepin and Phenytoin also act by blocking sodium channels in a voltage-dependent manner. Therefore, all of these drugs are effective in preventing seizures by modulating sodium channel function. The other choices (A, B, C) are incorrect because they individually target sodium channels through voltage-dependent inactivation, distinguishing them from other antiseizure drugs that act through different mechanisms.

Correct Answer: A

Rationale: Certainly! Chlorpromazine is the correct answer as it is a typical antipsychotic known to induce parkinsonian syndromes as a side effect due to its dopamine-blocking properties. This leads to a decrease in dopamine levels and imbalance in the basal ganglia function, resulting in symptoms resembling Parkinson's disease. Diazepam, Triazolam, and Carbamazepine do not typically induce parkinsonian syndromes as they do not directly affect dopamine levels or basal ganglia function.