The nurse administers a drug that stimulate the parasympathetic nervous system. What physiologic response would indicate that the drug is working?

A) Pupil dilation:
Pupil dilation is typically a response from stimulation of the sympathetic nervous system, not the parasympathetic system. The parasympathetic system tends to cause pupil constriction, so pupil dilation would not be an expected response to a parasympathetic agonist.

B) Increased gastrointestinal motility:
Stimulation of the parasympathetic nervous system, which is responsible for the "rest and digest" response, promotes the movement of food through the digestive tract, increasing gastrointestinal motility. This response is a classic sign that the parasympathetic system is being activated. Drugs that stimulate the parasympathetic nervous system often aim to enhance digestive functions.

C) Vasoconstriction:
Vasoconstriction is typically mediated by the sympathetic nervous system, not the parasympathetic system. The sympathetic nervous system activates alpha-adrenergic receptors that cause blood vessels to constrict, raising blood pressure. The parasympathetic system, on the other hand, typically promotes vasodilation, lowering blood pressure.

D) Increased heart rate:
Increased heart rate is generally associated with the sympathetic nervous system, which prepares the body for "fight or flight." The parasympathetic nervous system, in contrast, slows down the heart rate through vagal stimulation, so an increase in heart rate would not be the expected response to parasympathetic stimulation.

A) Excessive salivation: Neostigmine (Prostigmin) is a cholinesterase inhibitor, which works by increasing the levels of acetylcholine at neuromuscular junctions. If a dose is missed, excessive salivation can be a side effect of too much acetylcholine activity, but it is not the most immediate symptom in this case. Muscle weakness is a more direct consequence of a missed dose.

B) Respiratory paralysis: While respiratory weakness or paralysis can occur in myasthenia gravis, it is usually associated with a severe form of the disease or if the patient is in a myasthenic crisis. A single missed dose of neostigmine typically does not result in respiratory failure unless the patient is already in a very fragile state.

C) Muscle weakness: Neostigmine helps to improve neuromuscular transmission by inhibiting the breakdown of acetylcholine, which is crucial for muscle contraction. A missed dose would directly lead to a reduction in acetylcholine levels, exacerbating the characteristic muscle weakness of myasthenia gravis. Muscle weakness is the most anticipated symptom when neostigmine is not administered on time.

D) Muscle spasms: Muscle spasms are typically not a symptom of missed neostigmine therapy. Instead, muscle weakness occurs due to impaired neuromuscular transmission. Spasms might occur if there is significant overstimulation of the muscles, but this is more associated with electrolyte imbalances or other neuromuscular issues