What is the primary composition of brain tissue?

The primary composition of brain tissue consists of gray matter and white matter, making the first option the correct answer. Gray matter is primarily made up of neuronal cell bodies, dendrites, and unmyelinated axons, while white matter consists mostly of myelinated axons that connect different parts of the brain, facilitating communication between areas.

Gray matter is critical for processing information and executing functions such as thought, emotion, and memory. In contrast, white matter plays a vital role in transmitting signals across the brain and nervous system, ensuring that various brain regions can communicate efficiently.

The option stating "only gray matter" or "only white matter" does not accurately reflect the true structure of brain tissue, as both components are essential for the proper functioning of the brain. Cerebrospinal fluid, while important for cushioning and protecting the brain, does not constitute brain tissue itself but is found within the brain's ventricular system. Therefore, recognizing that brain tissue is composed of both gray and white matter is fundamental to understanding its anatomy and function.