Correct option is B
Explanation-
There are four main types of glial cells in the CNS:
1. Astrocytes- Maintain K⁺ balance, support neurons, form blood-brain barrier, help in repair
2. Oligodendrocytes - Form myelin sheath around CNS neurons
3. Microglia - Phagocytosis of debris/pathogens; immune defense
4. Ependymal cells - Line ventricles, circulate CSF via cilia
Statement A - Oligodendrocytes help maintain K⁺ level, and contribute to the blood-brain barrier - Incorrect
Oligodendrocytes primarily form the myelin sheath in CNS. The tasks mentioned here (K⁺ balance and blood-brain barrier maintenance) are actually the function of astrocytes, not oligodendrocytes.
Statement B- Microglia are capable of movement and phagocytosis of pathogens and damaged tissue - Correct
Microglia are the resident immune cells of the CNS. They are motile and perform phagocytosis of damaged neurons, debris, and pathogens. Their activity increases during CNS injury or infection.
Statement C - Astrocytes produce the myelin sheath to electrically insulate neurons of the CNS - Incorrect
Oligodendrocytes, not astrocytes, form the myelin sheath in the CNS. Astrocytes are more involved in metabolic support, ion regulation, neurotransmitter uptake, and forming the blood-brain barrier.
Statement D - Ependymal cells which are ciliated are involved in circulation of cerebrospinal fluid - Correct
Ependymal cells line the ventricles of the brain and the central canal of the spinal cord. Their cilia help in circulation of cerebrospinal fluid (CSF). Also involved in CSF production (via choroid plexus).
Incorrect Statement - A and C
Correct answer is option b - A and C
