A patient has a digoxin level of 1.4 ng/mL. The nurse interprets that this level is

Correct Answer: B

Rationale: The correct answer is B because a digoxin level of 1.4 ng/mL falls within the therapeutic range of 0.5-2 ng/mL. This level is appropriate for treating heart conditions effectively without causing toxicity. Choice A is incorrect because 1.4 ng/mL is within the therapeutic range. Choice C is incorrect as the level is not above the therapeutic range. Choice D is incorrect because a level of 1.4 ng/mL is not considered toxic.

Correct Answer: D

Rationale: The correct answer is D because hydrophilic substances cannot permeate membranes by passive diffusion due to their polarity and inability to dissolve in the hydrophobic lipid bilayer. This prevents them from crossing the membrane without the assistance of transport proteins. A, B, and C are incorrect because lipid-soluble, non-ionized substances, and hydrophobic substances can easily pass through membranes by passive diffusion as they can dissolve in the lipid bilayer.

Correct Answer: D

Rationale: The correct answer is D: cAMP. G-protein-coupled receptors activate adenylyl cyclase, leading to the production of cAMP, which acts as the second messenger. cAMP then triggers downstream signaling cascades. Choice A (Adenylyl cyclase) is the enzyme activated by G-protein-coupled receptors, not a second messenger itself. Choice B (Sodium ions) is not typically involved in GPCR signaling pathways. Choice C (Phospholipase C) generates inositol trisphosphate and diacylglycerol, which are part of a separate signaling pathway, not the second messenger system for GPCRs.

Correct Answer: A

Rationale: The correct answer is A because Type A delta and C fibers are known to participate in high-frequency pain transmission. Type A delta fibers transmit sharp, localized pain signals, while Type C fibers transmit dull, aching pain signals. Choice B, Type A alpha fibers, are responsible for transmitting proprioceptive information. Choice C, Type B fibers, are not involved in pain transmission. Choice D, Type A beta fibers, are responsible for touch and pressure sensations, not high-frequency pain transmission. Therefore, based on the characteristics of each fiber type, Type A delta and C fibers are the correct choice for high-frequency pain transmission.

Correct Answer: A

Rationale: The correct answer is A: Physostigmine, which penetrates the blood-brain barrier. Physostigmine is a reversible cholinesterase inhibitor that can cross the blood-brain barrier, allowing it to exert its effects on cholinesterase enzymes in the central nervous system. This property makes it useful in conditions where increasing cholinergic activity in the brain is desired, such as in the treatment of Alzheimer's disease. Choice B, Edrophonium, is a reversible cholinesterase inhibitor but does not effectively penetrate the blood-brain barrier. Choice D, Neostigmine, is also a reversible cholinesterase inhibitor but is primarily used for its effects on peripheral cholinesterase enzymes and does not cross the blood-brain barrier effectively.