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Lecture 6

Week 6 - Structure of the Nervous System

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Ryerson University
PSY 324
Ayesha Khan

Week 6 Structure of the Nervous SystemOctober0511437 PMBasic Features of the Nervous SystemDescribing DirectionsDirections in the nervous system are generally described relative to the neuraxis an imaginary line drawn through the spinal cord up to the front of the brainThe front end is anteriorand the back end is posterior The terms rostraltoward the beak and caudal toward the tail are also usedThe top of the head and the back are part of the dorsalsurface while the ventralfront surface includes our frontSuperior means above and inferior means belowLateralmeans toward the outside and medial means toward the midlineBrain Slices and PlainsWe can slice the nervous system in three waysTransversely giving us cross sectionsParallel to the ground giving us horizontal sectionsPerpendicular to the ground and parallel to the neuraxis giving us sagittal sections The midsagittal plane divides the brain into two symmetrical halvesAn OverviewThe nervous system consists of the brain and spinal cord which make up the central nervous system CNSThe CNS is encased in bone the brain is covered by the skull and the spinal cord is encased by the vertebral columnThe cranial nerves spinal nerves and peripheral ganglia constitute the peripheral nervous system PNSMeningesThe entire nervous systembrain spinal cord cranial and spinal nerves and peripheral gangliais covered by tough connective tissue The protective sheaths around the brain and spinal cord are referred to as the meninges Meninges consist of three layersThe outer layer is thick tough and flexible but unstretchable its name the dura mater means hard motherThe middle layer the arachnoid membrane gets its name from the weblike appearance of the arachnoid trabeculae that protrude from it It lies beneath the dura materThe pia materis closely attached to the brain and spinal cord and follows every convolution The smaller surface blood vessels of the brain and spinal cord are contained within this layerBetween the pia mater and the arachnoid membrane is a gap called the subarachnoid spaceThis space is filledwith cerebrospinal fluidThe PNS is covered with two layers of meningesThe Ventricular System and Production of Cerebrospinal FluidThe brain floats in a bath of CSF contained in the subarachnoid space This reduces the weight of the brain and the pressure of the brain is greatly diminishedThe CSF around the brain and spinal cord also reduces the shock from a sudden movementThe brain contains a series of hollow interconnected chambers called ventricles little bellies which are filled with CSFThe largest chambers are the two lateral ventricles which are connected to the third ventricleThe cerebral aqueduct a long tube connects the third ve
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