Human brain structure and function

Brain as central organ of nervous system

The brain is the central organ of the human nervous system and, together with the spinal cord, forms the central nervous system (CNS). It is composed of three major parts—the cerebrum, brainstem, and cerebellum—and it controls and coordinates most body activities by processing, integrating, and directing information received from the sensory nervous system to the rest of the body. The cerebrum is the largest component and includes two cerebral hemispheres, each with an outer cerebral cortex (gray matter) and an inner core of white matter. The cortex is organized into lobes (frontal, parietal, temporal, occipital) with specialized roles such as executive functions and reasoning (frontal lobe) and vision (occipital lobe). The hemispheres communicate via commissural tracts, especially the corpus callosum, and the brainstem connects the cerebrum to the spinal cord. The cerebellum supports coordination and balance, while the brain is protected by the skull, suspended in cerebrospinal fluid, and shielded from the bloodstream by the blood–brain barrier. Brain function depends on vast neural interconnections and neurotransmission, and the brain is vulnerable to injury, stroke, degenerative diseases, infections, tumors, and psychiatric or neurological dysfunctions.

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Central nervous system components: brain and spinal cord

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