All are features of organophosphorus poisoning except
**Core Concept**
Organophosphorus poisoning is a type of chemical toxicity caused by exposure to organophosphorus compounds, which are commonly found in pesticides and nerve agents. These compounds inhibit the enzyme acetylcholinesterase, leading to an accumulation of acetylcholine in the nervous system and resulting in a range of systemic effects.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of organophosphorus poisoning, specifically the inhibition of acetylcholinesterase. This enzyme is responsible for breaking down acetylcholine, a neurotransmitter that plays a crucial role in the transmission of nerve impulses. When acetylcholinesterase is inhibited, acetylcholine builds up in the synapses, leading to overstimulation of muscarinic and nicotinic receptors, resulting in symptoms such as bradycardia, bronchospasm, and muscle fasciculations.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because organophosphorus poisoning is characterized by an overdose of acetylcholine, which leads to overstimulation of muscarinic and nicotinic receptors, resulting in symptoms such as bradycardia, bronchospasm, and muscle fasciculations. This is in contrast to atropine poisoning, which is characterized by an underdose of acetylcholine, leading to anticholinergic symptoms such as tachycardia, dry mouth, and blurred vision.
* **Option B:** This option is incorrect because organophosphorus poisoning is associated with an increase in acetylcholine levels, leading to overstimulation of muscarinic and nicotinic receptors, resulting in symptoms such as bradycardia, bronchospasm, and muscle fasciculations. This is in contrast to botulism, which is characterized by a decrease in acetylcholine release, leading to flaccid paralysis and respiratory failure.
* **Option C:** This option is incorrect because organophosphorus poisoning is associated with an increase in acetylcholine levels, leading to overstimulation of muscarinic and nicotinic receptors, resulting in symptoms such as bradycardia, bronchospasm, and muscle fasciculations. This is in contrast to tetanus poisoning, which is characterized by an abnormal increase in muscle tone, resulting in rigidity and spasms.
**Clinical Pearl / High-Yield Fact**
A key feature of organophosphorus poisoning is the presence of miosis (pupil constriction), which is due to the overstimulation of muscarinic receptors by excess acetylcholine. This is in contrast to atropine poisoning, which is characterized by mydriasis (pupil dilation).
**Correct Answer: B. Botulism**