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Central Nervous System.docx

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PSYC 494N1
Geraldine Akman

 The Central Nervous System o Consists of the parts of the nervous system encased in bone: the brain and the spinal cord o Three parts of the brain are common to all mammals: the cerebrum, the cerebellum, and the brain stem o The Cerebrum  Rostral-most and largest part of the brain  It is split down the middle into two hemispheres; separated by the deep sagittal fissure.  The right hemisphere receives information and controls the left side of the body; the left hemisphere receives information and controls the right side of the body o The Cerebellum  Lies behind the cerebrum  It contains as many neurons as both cerebral hemispheres combined  It is primarily a movement control center with extensive connections to the cerebrum and spinal cord  Left side of the cerebrum is concerned with the left side of the body and the same applies to the right portion. o The Brain Stem  The remaining part of the brain  Forms the stalk from which the cerebral hemispheres and the cerebellum sprout  A complex nexus of fibers and cells that in part serves to relay information from the cerebrum to the spinal cord and cerebellum; and vice versa  Also the site where vital functions are regulated (e.g. breathing, consciousness, and the control of body temp.)  Considered the most primitive part of the mammalian brain but also the most important to life o The Spinal Cord  Encased in a bony vertebral column and is attached to the brain stem  Is the major conduit of info from skin, joints, and muscles of the body to the brain and vice versa  It communicates with the body via the spinal nerves (part of PNS).  Each spinal nerve attaches to the spinal cord by means of two branches: the dorsal root and the ventral root  The Peripheral Nervous System o Has two parts: the somatic PNS and the visceral PNS o The Somatic PNS  All the spinal nerves that innervate the skin, the joints, and the muscles that are under voluntary control are part of this PNS  The somatic motor axons (command muscle contraction) derives from motor neurons in the ventral spinal cord  The cell bodies of the motor neurons lie within the CNS, but their axons are mostly in the PNS  The somatic sensory axons enter the spinal cord via the dorsal ro
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