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A&P OPENSTAXCHAPTER13 : NERVOUS SYSTEM13.1 The Central Nervous System ( BRAIN )A.The brain is the largest and most complex portion of the nervous system.It occupies the cranial cavityand is composed of one hundred billion multipolar neurons.B.Cerebrum=the largestportion of the brain, which is divided intotwo cerebral hemispheres1.Anatomy of Cerebruma.Conscious thought, memory storage and processing, sensory processing, and theregulation of skeletal muscle contractions.b.The surface of the cerebrum is highly folded and covered with a superficial layer of graymatter called thecerebral cortex.a.Fissures= deep grooves1.longitudinal fissureseparates the two cerebral hemispheres.2.transverse fissure(separates cerebrum from cerebellum)b.Sulci(sulcus) = shallow depressions that separate the folds or wrinkles1.central sulcus(separates frontal lobe from parietal lobe)2.lateral sulcus(separates frontal and parietal lobes from temporal lobe)c.Gyri(gyrus) = elevated regions that increase surface area1.precentral gyrus(motor cortex)2.postcentral gyrus(somatosensory cortex)c.Each cerebral hemisphere is further subdivided intolobes.There are five lobes:thefrontal, parietal, occipital, temporal, and insula (deep).
d.The gyrus immediately anterior to the central sulcus is called theprecentral gyruswhilethe gyrus immediately posterior the central sulcus is called thepostcentral gyrus.e.Gray matter = neuron cell bodies and unmyelinated axons.f.White matter=myelinated axons. For example thecorpus callosumprovides themajor pathway for communication between the two hemispheres of the cerebral cortexg.Nuclei – term for clusters of cell bodies belonging to many neuronsh.Tracts – pathways formed by large groups of axons that run together2.Important features of cerebruma.Cerebrum functions include conscious thought, memory storage and processing,sensory processing, and the regulation of skeletal muscle contractions.b.Thecerebral cortexis the GRAY matter of the cerebrum and is responsible for allqualities associated with “consciousness”.c.Each hemisphere is concerned with the sensory and motor functions of the opposite sideof the body (contralateral)d.Thetwo hemispheresare not equal in function, though symmetrical in structure. Insteadthere iscerebrallateralizationor specialization of the cortical functionsi.Right brain= analyzes sensory information and relates the body to the sensoryenvironment; interpretive centers in this hemisphere enable you to identifyfamiliar objects by touch, sight, smell, taste, or feel.Right brained individuals areoften more artistic, musically inclined, or attuned to their emotions.ii.Left brain= possesses the general interpretive and speech centers and isimportant in language-based skills; important in reading, writing, speaking, math,and logic.