In a patient given a cardiac glycoside, important effects of the drug on the heart include which of the following?

Correct Answer: D

Rationale: In this scenario, the correct answer is D) All of the above. When a patient is given a cardiac glycoside, such as digoxin, it exerts multiple effects on the heart. A) Decreased atrioventricular conduction velocity: Cardiac glycosides like digoxin can indeed decrease atrioventricular conduction velocity, which can lead to a decrease in heart rate and potentially help in managing certain cardiac conditions like atrial fibrillation. B) Decreased ejection time: Cardiac glycosides can prolong the ejection time by increasing the contractility of the heart muscle, leading to more efficient ejection of blood from the heart. C) Increased ectopic automaticity: Cardiac glycosides can also increase ectopic automaticity, which refers to abnormal electrical activity in the heart, potentially leading to arrhythmias. Educationally, understanding the effects of cardiac glycosides on the heart is crucial for healthcare professionals, especially those working in cardiology or critical care settings. Knowing these effects helps in assessing the patient's response to the medication, monitoring for potential side effects, and adjusting treatment plans as needed. It also highlights the importance of close monitoring and patient education when administering drugs that can have significant impacts on cardiac function.

Correct Answer: C

Rationale: In this scenario, the correct answer is C) Mexiletine. Mexiletine is a Class IB antiarrhythmic drug that is orally active and works by blocking sodium channels, thus decreasing action potential duration. This mechanism of action helps in regulating abnormal heart rhythms. Option A) Adenosine is not the correct answer because it works by activating adenosine receptors and is used for treating supraventricular tachycardia, not by blocking sodium channels. Option B) Amiodarone is a Class III antiarrhythmic drug that prolongs action potential duration by blocking potassium channels, so it does not fit the description given in the question. Option D) Esmolol is a beta-blocker that works by blocking beta-adrenergic receptors, leading to a decrease in heart rate and contractility. It does not block sodium channels or affect action potential duration. In an educational context, understanding the mechanisms of action of different drugs is crucial for healthcare professionals, especially those involved in managing cardiac conditions. Knowing how each drug affects ion channels and action potentials helps in selecting the most appropriate medication for a specific arrhythmia based on its underlying pathophysiology. This knowledge is essential for optimizing patient outcomes and preventing potential adverse effects.

Correct Answer: B

Rationale: In the context of peripheral nervous system drugs, understanding the specificity of drug actions on different muscarinic receptor subtypes is crucial. Oxytremorine, a parasympathomimetic drug, is indeed a selective agonist of muscarinic receptors, particularly targeting the M2 subtype. The correct answer is B) M2 because oxytremorine primarily acts on M2 muscarinic receptors. Activation of M2 receptors leads to various physiological responses, such as decreased heart rate and decreased contractility in the heart, which are consistent with the effects of oxytremorine. Option A) M1 is incorrect because oxytremorine has minimal affinity for M1 receptors. Option C) M3 is incorrect as oxytremorine has minimal to no affinity for M3 receptors, which are typically targeted by drugs like pilocarpine. Option D) M4 is also incorrect as oxytremorine does not significantly interact with M4 receptors. Educationally, understanding the specific receptor targets of drugs helps in predicting their physiological effects and potential side effects. This knowledge is fundamental for healthcare professionals in prescribing the right medication for a patient's condition and avoiding adverse reactions. It also underscores the importance of drug selectivity in achieving desired therapeutic outcomes with minimal off-target effects. In conclusion, grasping the selectivity of drugs like oxytremorine for specific muscarinic receptor subtypes enhances pharmacological knowledge and clinical decision-making, ultimately improving patient care and treatment efficacy in the realm of peripheral nervous system pharmacology.

Correct Answer: C

Rationale: The correct answer is C) Calcitriol is the major derivative responsible for increasing intestinal absorption of phosphate. Explanation: - Calcitriol, the active form of Vitamin D, plays a crucial role in regulating calcium and phosphate metabolism. It acts on the intestines to enhance the absorption of both calcium and phosphate. While calcium absorption is a well-known function of Vitamin D, its role in increasing phosphate absorption is equally important for maintaining bone health and overall mineral balance in the body. Why the other options are incorrect: A) Vitamin D actually acts to increase serum levels of calcium by enhancing its absorption in the intestines and promoting its reabsorption in the kidneys. B) Activation of Vitamin D receptors leads to the production of proteins involved in calcium and phosphate homeostasis, not cAMP. D) Vitamin D and its metabolites actually help in increasing the renal reabsorption of calcium to maintain adequate levels in the body, rather than promoting its excretion. Educational context: Understanding the functions of Vitamin D and its metabolites is essential for healthcare professionals, especially those working with patients at risk of bone disorders or mineral imbalances. Knowing the role of calcitriol in regulating phosphate absorption is crucial for managing conditions like osteoporosis, renal bone disease, and other metabolic disorders. This knowledge helps in making informed decisions regarding the use of Vitamin D supplements and other treatment options for maintaining optimal bone health.

Correct Answer: D

Rationale: The correct answer is D) All of the above. The action of norepinephrine and epinephrine are terminated by a combination of processes, not just one singular mechanism. Understanding this concept is crucial in pharmacology and neurophysiology. A) Reuptake into nerve terminal is one way these neurotransmitters are terminated, where they are taken back up into the presynaptic neuron for recycling or storage. B) Dilution by diffusion and uptake at extraneuronal site involves the neurotransmitters diffusing away from the synaptic cleft and being taken up by other cells or tissues, reducing their concentration and effect. C) Metabolic transformation occurs when norepinephrine and epinephrine are broken down by enzymes like monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT), leading to their inactivation. Understanding these mechanisms is vital for healthcare professionals as it helps in comprehending the effects and duration of action of drugs that target the peripheral nervous system. Mastery of these concepts is essential for safe and effective medication administration and patient care.