NERVOUS SYSTEM 2.ppt - NERVOUS SYSTEM Objectives • • • • •...

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NERVOUS SYSTEM
ObjectivesDefine CNSExplain how the nervous system is protectedDescribe the meningesDescribe CSFDescribe ventricles of the brainDescribe the brain
Objective 1: Define CNSIt is formed by the brain and the spinal cordIt forms the control centre of all activities inthe body.
Objective 2: Explain Protection ofthe CNSThe brain is protected by:Cranial bonesThe spinal cord protected by the vertebralcolumnBoth brain and spinal cord are protected by:MeningesCerebrospinal fluid
Objective 3: Describe theMeningesThree connective tissue membranes lieexternal to the CNSdura materarachnoid materpia materFunctions of the meningesCover and protect the CNSContain cerebrospinal fluid (CSF)Form partitions within the skull
MeningesFigure 12.23a
Dura MaterLeathery, strong meninx composed of twofibrous connective tissue layersThe two layers separate in certain areas andform dural sinuses.It forms the outer layer of the meninges andinner periosteum of cranial bones.
Three dural septa extend inward and limitexcessive movement of the brainFalx cerebri – fold that dips into the longitudinalfissure between the two hemispheresFalx cerebelli – separates the 2 hemispheres of thecerebellumTentorium cerebelli – horizontal dural fold extendsinto the transverse fissure ie separates thecerebrum from the cerebellum.
Dura MaterFigure 12.24
Arachnoid MaterThe middle layer, which forms a loose braincoveringIt is separated from the dura mater by thesubdural space which contains lubricatingserousfluid.Beneath the arachnoid is a wide subarachnoidspace filled with CSF and large blood vesselsArachnoid villi protrude superiorly and permitCSF to be absorbed into venous blood
Arachnoid MaterFigure 12.23a
Pia MaterThe innermost layer composed of delicateconnective tissue that clings tightly to the brain
Objective 4: DescribeCerebrospinal Fluid (CSF)Watery solution similar in composition to bloodplasma produced by choroid plexus in eachventricle.
FunctionsForms a liquid cushion that gives buoyancy tothe CNS organsPrevents the brain from crushing under itsown weightProtects the CNS from blows and othertraumaNourishes the brain and carries chemicalsignals throughout it
Composition of CSFWaterMineral saltsProteins eg albumin,globulinGlucoseUreaFew leukocytes
Objective 5: Describe Ventricles ofthe BrainThese are hollow chambers with CSF and linedwith ependymal cellsThe ventricles are:The paired C-shaped lateral ventricles i.e. the rightand the left ventricles.The third ventricle found in the diencephalonThe fourth ventricle found in the hindbrain dorsalto the pons
Lateral ventriclesThey are located within each hemisphere andare separated by a thin membrane calledseptum pellucidum.

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