Which of the following is the site of action of strychnine poison for its toxicity?
**Core Concept**
The underlying principle being tested is the understanding of the neurotoxic effects of **strychnine**, a potent inhibitor of **glycine receptors** in the central nervous system. **Strychnine** acts by blocking the inhibitory effects of glycine, leading to an increase in neuronal excitability. This results in muscle convulsions and eventually death.
**Why the Correct Answer is Right**
The correct site of action of strychnine is the **spinal cord**, where it inhibits the release of **glycine**, an inhibitory neurotransmitter. By blocking glycine receptors, strychnine removes the inhibitory control over neuronal activity, leading to an exaggerated response to stimuli and resulting in muscle spasms and convulsions. The **spinal cord** is the primary site where this action occurs, as it is rich in glycine receptors that regulate motor neuron activity.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while the brain is affected by strychnine toxicity, it is not the primary site of action.
**Option B:** Incorrect as it is not directly related to the mechanism of strychnine toxicity.
**Option D:** Incorrect because, although strychnine can affect various parts of the nervous system, its primary toxic effect is not at this site.
**Clinical Pearl / High-Yield Fact**
Remember that **strychnine poisoning** presents with muscle rigidity and convulsions without significant depression of the CNS, distinguishing it from other neurotoxins. The key to diagnosing strychnine poisoning is recognizing the rapid onset of severe muscle spasms.
**Correct Answer:** C. Spinal cord.