Human brain structure and function

Brain as central organ of the nervous system

The brain is the central organ of the nervous system and, together with the spinal cord, forms the central nervous system (CNS). It is composed of three main parts—the cerebrum, brainstem, and cerebellum. The brain processes, integrates, and coordinates information received from the sensory nervous system and uses this information to control most body activities by sending instructions to the rest of the body. Structurally, the cerebrum is the largest portion and is divided into two cerebral hemispheres. Each hemisphere contains white matter in its inner core and grey matter on its outer surface (the cerebral cortex). The cortex includes the neocortex and allocortex, and the hemispheres are organized into lobes (frontal, parietal, temporal, occipital) with specialized roles such as executive functions and vision. The hemispheres are connected by commissural tracts, especially the corpus callosum, while the brainstem connects the cerebrum to the spinal cord and supports essential functions like breathing and eye movement control. The brain is protected by the skull and suspended in cerebrospinal fluid, with additional protection from the blood–brain barrier, but it remains vulnerable to injury, stroke, disease, and infection.

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Major brain parts: cerebrum, brainstem, cerebellum

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