CNS

Central nervous system (CNS) is one of the two main divisions of the nervous system, consisting of the brain and spinal cord. It processes sensory information, coordinates motor responses, and underlies cognition, emotion, and behavior. The CNS integrates signals, stores memories, and orchestrates complex activities such as language and planning. It is protected by the skull and vertebral column and surrounded by three membranes called the meninges: dura mater, arachnoid mater, and pia mater. Cerebrospinal fluid cushions the CNS and circulates within the ventricular system and subarachnoid space. The blood-brain barrier, formed in part by astrocyte endfeet and tight junctions of brain capillaries, regulates substance passage between the bloodstream and neural tissue.

Anatomically, the brain comprises the cerebrum, cerebellum, brainstem, and diencephalon. The cerebrum handles higher functions; the cerebellum coordinates movement and balance; the brainstem controls autonomic functions and relays signals. The spinal cord transmits information between the brain and the body and houses reflex circuits. Neurons and glial cells, including myelinating oligodendrocytes, form networks that underlie processing and communication.

Developmentally, the CNS arises from the neural tube during early embryogenesis and undergoes differentiation, myelination, and synaptic pruning. Clinically, CNS pathology includes neurodegenerative diseases, stroke, multiple sclerosis, spinal cord injury, infections, and epilepsy. Diagnosis relies on imaging such as MRI and CT, electrophysiology like EEG, and analysis of cerebrospinal fluid.

Compared with the peripheral nervous system, the CNS functions as an autonomous control center but remains connected to the body through cranial and spinal nerves and autonomic pathways.