human brain

The adult human brain houses an estimated 100 billion to 1 trillion neurones, forming a massive network of axons, dendrites, and cell bodies. These cells and their networks give form and function to the brain, which in humans makes up roughly 2 percent of an adult’s body weight.

The human brain has three major parts, the cerebrum, cerebellum, and brainstem. The cerebrum is the largest of the three and is known for its convoluted (wrinkled) surface. It is divided into two hemispheres—left and right—which carry out complex, or “higher,” functions, such as problem solving, integrating and interpreting sensory information, and forming and storing memories. The cerebellum, which is located below and behind the cerebral hemispheres, is responsible for coordinating muscle movements and controlling balance. Both the cerebrum and cerebellum are composed of gray matter, which consists primarily of neuroglia and unmyelinated neurons, and white matter, which mostly is made up of myelinated neurons. The brainstem lies at the base of the brain and between the deep tissues of the cerebral hemispheres and the cervical portion of the spinalcord. Its primary role is as a control center for basic, “automatic” body functions, such as breathing and swallowing.

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