Final answer:
The statement is true; myelinated fibers within the brain and spinal cord are known as white matter, which is essential for rapid communication in the nervous system.
Step-by-step explanation:
The statement "Myelinated fibers within the brain are known as white matter" is true. White matter is a type of nervous tissue that is found in the brain and the spinal cord. It consists mainly of axons that are covered with a myelin sheath, giving them a lighter appearance than the non-myelinated parts of the nervous system. This myelin sheath is crucial as it insulates the axons and increases the speed of electrical signals (or action potentials) along the axons, which facilitates rapid communication between different regions of the brain and between the brain and the spinal cord.
White matter, therefore, plays a vital role in the fast transmission of information through the nervous system. Axons within white matter can be quite long; in adult humans they may be more than a meter, such as those extending from the base of the spine to the toes. This is important for the efficient operation of the nervous system across the vast network of neurons that span our body.