Which type of tissue is characterized by the presence of myelin?

The presence of myelin is a defining characteristic of white matter in the nervous system. Myelin is a fatty substance that surrounds and insulates the axons of neurons, facilitating the rapid transmission of electrical signals along the nerve fibers. This myelinated structure is what gives white matter its distinctive color when viewed in a cross-section of the brain or spinal cord, as the myelin content contrasts with the neuronal cell bodies and unmyelinated fibers found in grey matter.

In contrast, grey matter primarily consists of neuronal cell bodies, dendrites, and unmyelinated axons, which is why it appears darker. While brain tissue and nervous tissue include both grey and white matter, the specific identification of white matter focuses solely on the presence of myelin. Therefore, the recognition of myelin as a key feature leads directly to the conclusion that the correct answer points to white matter as the type of tissue characterized by this crucial insulating material.