**Core Concept:**
Strychnine is a highly toxic alkaloid found in plants of the Strychnos genus, particularly in seeds of the Strychnos nux-vomica plant. It works by blocking the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) receptors, leading to excessive stimulation of the central nervous system.

**Why the Correct Answer is Right:**
Strychnine poisoning is characterized by its effects on the central nervous system. In this case, the correct answer is **D:** The spinal cord is preserved in strychnine poisoning. The toxic effects of strychnine primarily involve the inhibition of GABAA receptors, leading to overstimulation of neurons and spasticity, tachypnea, and increased intracranial pressure. However, the spinal cord, being a part of the peripheral nervous system, is less affected by strychnine as compared to the central nervous system, which includes the brain and brainstem.

**Why Each Wrong Option is Incorrect:**
A) The brain is predominantly affected in strychnine poisoning due to its involvement in the central nervous system, making it an incorrect choice.
B) Although the peripheral nervous system is less severely affected than the central nervous system, the spinal cord is still involved, which makes this option incorrect as well.
C) The skeletal muscles are affected by strychnine poisoning due to its inhibition of neuromuscular junctions, but this is not the primary organ preserved in strychnine poisoning.

**Clinical Pearl / High-Yield Fact:**
Strychnine poisoning can present with a characteristic "double pattern" electroencephalogram (EEG) pattern, characterized by a burst-suppression pattern followed by a spike-wave pattern, which is often used to diagnose the condition. This feature is particularly useful for clinical examiners assessing patients with unexplained seizures or abnormal neurological findings.