OCR GCSE Biology Practice Exam 2025 – Comprehensive All-in-One Guide to Exam Success

The central nervous system (CNS) is primarily composed of the brain and spinal cord. The brain serves as the control center for the entire body, processing sensory information, controlling movement, and managing higher functions such as reasoning and emotion. The spinal cord acts as a vital communication pathway between the brain and the rest of the body, transmitting signals that coordinate reflexes and voluntary movements.

The CNS is distinct from the peripheral nervous system, which includes all the nerves outside the brain and spinal cord. While neurons are essential components of the CNS, they are not the only components, and hormones are regulated by the endocrine system, not directly part of the CNS. Muscles and glands are effectors and are influenced by the nervous system but are not components of it. Similarly, sensory neurons and receptors are associated with the peripheral nervous system, which sends information to the CNS rather than being part of it.