All are features of acute morphine poisoning, except: Kerala 11; MAHE 12
**Core Concept**
Morphine poisoning occurs due to the excessive accumulation of morphine in the body, leading to its central nervous system (CNS) effects. Morphine acts on the opioid receptors in the brain, altering the perception of pain and producing various systemic effects.
**Why the Correct Answer is Right**
Morphine poisoning is characterized by several symptoms, including respiratory depression, miosis (pupil constriction), sedation, and hypotension. The mechanism behind these effects involves morphine's action on the mu-opioid receptors in the brain, which reduces the release of neurotransmitters such as dopamine, norepinephrine, and acetylcholine. This results in a decrease in respiratory rate, blood pressure, and consciousness.
**Why Each Wrong Option is Incorrect**
**Option A:** Hypertension is incorrect because morphine typically leads to hypotension due to its vasodilatory effects and decreased sympathetic tone.
**Option B:** Tachypnea is incorrect because morphine causes respiratory depression, leading to a decrease in respiratory rate.
**Option C:** Mydriasis (pupil dilation) is incorrect because morphine causes miosis, which is the constriction of the pupils.
**Clinical Pearl / High-Yield Fact**
Morphine poisoning can be treated with naloxone, an opioid antagonist that reverses the effects of morphine by competitively binding to the mu-opioid receptors.
**Correct Answer: C. Mydriasis.**