This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: NEET Jan 2020, Subject name: Medicine
In Multiple sclerosis, Where does the defect occur? 
Select and explain. 
A. Oligodendrocytes, B. Myelin sheath, C. Node of Ranvier, D. Neuroglial cells
B: Myelin sheath
Answer: B: Myelin sheath 
Explanation: Multiple sclerosis Autoimmune condition Attacks the myelin sheath in the brain and spinal cord. Layer that surrounds the nerves, protect them and help electrical signals travel from the brain to the rest of the body. Autoimmune attacks cause the myelin sheath to become inflamed in a small patches (plaques or lesions), which can be seen on an MRI Scan. These patches of inflammation can disrupt the messages travelling along the nerves.