What liquid circulates throughout the spaces within the brain and spinal cord?

Cerebrospinal fluid is the liquid that circulates throughout the spaces within the brain and spinal cord. It plays a critical role in protecting the central nervous system, serving as a cushion that absorbs shock and reduces the risk of injury. Additionally, cerebrospinal fluid helps maintain intracranial pressure and provides essential nutrients to the brain while removing waste products.

In contrast, synovial fluid is found in joint cavities, serving to lubricate and cushion joints, rather than in the central nervous system. Blood plasma is the liquid component of blood and is involved in transporting nutrients, gases, and hormones throughout the body, but it does not circulate within the brain and spinal cord. Lymph is a fluid that is part of the lymphatic system and plays a role in immune function, not in the central nervous system. Thus, cerebrospinal fluid is the only correct answer when considering the specific function and location within the brain and spinal cord.