MY LIFE

brain. A large, highly organized complex of neuron cell bodies, axons, dendrites, and glia filling the cavity inside the skull; the brain is enveloped by fluid-filled protective membranes (meninges).

ANATOMY
The brain is a soft, compact organ responsible for consciousness, planned neural programs, and cognition. The brain is continually active, and, although it is only 2% of the body’s mass, it receives 17% of the heart's output and consumes 20% of the body's oxygen supply. The brain receives its blood through four arteries: two large arteries, the right and left internal carotid arteries, run up from the chest in the front (anterior half) of the neck; and two smaller arteries, the right and left vertebral arteries, run in the back (posterior half) of the neck. The carotid arteries supply blood to about 80% of the brain, including most of the frontal, parietal, and temporal lobes of the cerebral hemispheres and the basal ganglia. The vertebral arteries supply blood to the remaining 20% of the brain, including the brainstem, cerebellum, and most of the posterior lobes of the cerebral hemispheres.