Pralidoxime is a cholinesterase reactivator used in the treatment of toxicity by:

Correct Answer: C

Rationale: The correct answer is C: Organic phosphate. Pralidoxime is used to treat toxicity caused by organophosphates, which inhibit cholinesterase enzymes. Pralidoxime works by reactivating the inhibited cholinesterase enzymes, restoring their function. Atropine is used to counteract the effects of excessive acetylcholine in cholinergic toxicity, not organophosphate poisoning. Nicotine is a nicotinic receptor agonist and not treated with pralidoxime. Amphetamine is a central nervous system stimulant and does not involve cholinesterase inhibition. Therefore, the correct answer is C as pralidoxime is specifically used to treat toxicity caused by organophosphates.

Correct Answer: D

Rationale: The correct answer is D because physostigmine is used in the treatment of glaucoma due to its ability to lower intraocular pressure. It works by inhibiting the enzyme acetylcholinesterase, leading to increased levels of acetylcholine which helps in constricting the pupil and improving drainage of fluid in the eye. Options A and C are incorrect as physostigmine is a tertiary amine and a reversible anti-cholinesterase. Option B is incorrect as physostigmine does have CNS action, crossing the blood-brain barrier and affecting brain function.

Correct Answer: D

Rationale: The correct answer is D because anticholinesterase drugs are not bronchodilators; they actually increase cholinergic activity by inhibiting the breakdown of acetylcholine. Reversible and irreversible types do exist (A), neostigmine and physostigmine are examples (B), and they can cause miosis and lacrimation due to increased cholinergic activity (C). Hence, D is the incorrect statement.

Correct Answer: C

Rationale: Rationale: Edrophonium is used to differentiate myasthenia crisis and cholinergic crisis by temporarily improving muscle weakness in myasthenia crisis but worsening symptoms in cholinergic crisis. Neostigmine (A) and Succinylcholine (D) can exacerbate cholinergic crisis. Hyoscine (B) is not used for this purpose.

Correct Answer: B

Rationale: The correct answer is B: Noradrenaline. Sympathetic nerve fibers release noradrenaline as the primary neurotransmitter to activate the fight-or-flight response. Noradrenaline acts on adrenergic receptors to increase heart rate, blood pressure, and blood flow to muscles. Epinephrine (choice A) is also released in the sympathetic nervous system but mainly by the adrenal glands. Acetylcholine (choice C) is the primary neurotransmitter in the parasympathetic nervous system. Acetylcholinesterase (choice D) is an enzyme that breaks down acetylcholine and is not a neurotransmitter.