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Brain (Front Cutaway) The brain is the primary component of the nervous system, occupying the cranial cavity. Without its outermost protective membrane, the dura mater, the brain weighs an average of three pounds (about 1.4 kilograms), comprising about 97% of the entire central nervous system. The brain is connected to the upper end of the spinal cord (which connects through the foramen magnum of the skull) and is responsible for issuing nerve impulses, processing nerve impulse data, and engaging in the higher order thought processes. The brain is divided into three parts: the large cerebrum, the smaller cerebellum, and the brainstem leading to the spinal cord. The brainstem is also descriptively divided into the medulla oblongata, the midbrain, and the pons. Cerebellum The cerebellum is second smaller division of the brain, located below the cerebrum and in the posterior of the brain. The cerebellum features a central portion, called the vermis, and two side portions, or hemispheres - one on each side. It is the responsibility of the cerebellum to coordinate and modify the resultant activity of impulses and orders sent from the cerebrum. It does this by receiving information from nerve endings all over the body, such as the balance and equilibrium centers in the inner ear, and adjusts and fine tunes these actions by passing the regulating signals to the motor neurons of the brain and spinal cord.
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