Tortora - Chapter 14 - The Brain and Cranial Nerves

Tortora - Chapter 14 - The Brain and Cranial Nerves -...

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Unformatted text preview: 14-1Chapter 14The Brain and Cranial NervesLargest organ in the body at almost 3 lb.Brain functions in sensations, memory, emotions, decision making, behavior14-2Principal Parts of the BrainCerebrumDiencephalonthalamus & hypothalamusCerebellumBrainstemmedulla, pons & midbrain14-3Protective Coverings of the BrainBone, meninges & fluidMeninges same as around the spinal corddura materarachnoid materpia materDura mater extensionsfalx cerebritentorium cerebellifalx cerebelli14-4Blood Supply to BrainArterial blood supply is branches from circle of Willis on base of brain (page 699)Vessels on surface of brain----penetrate tissueUses 20% of our bodies oxygen & glucose needsblood flow to an area increases with activity in that areadeprivation of O2 for 4 min does permanent injuryat that time, lysosome release enzymesBlood-brain barrier (BBB)protects cells from some toxins and pathogensproteins & antibiotics can not pass but alcohol & anesthetics dotight junctions seal together epithelial cells, continuous basement membrane, astrocyte processes covering capillaries14-5Cerebrospinal Fluid (CSF)80-150 ml (3-5oz)Clear liquid containing glucose, proteins, & ionsFunctionsmechanical protection floats brain & softens impact with bony wallschemical protectionoptimal ionic concentrations for action potentialscirculationnutrients and waste products to and from bloodstream14-6Origin of CSFChoroid plexus = capillaries covered by ependymal cells2 lateral ventricles, one within each cerebral hemisphereroof of 3rd ventriclefourth ventricle14-7Drainage of CSF from VentriclesOne median aperture & two lateral apertures allow CSF to exit from the interior of the brain14-8Flow of Cerebrospinal Fluid14-9Reabsorption of CSFReabsorbed through arachnoid villigrapelike clusters of arachnoid penetrate dural venous sinus20 ml/hour reabsorption rate = same as production rate14-10HydrocephalusBlockage of drainage of CSF (tumor, inflammation, developmental malformation, meningitis, hemorrhage or injuryContinued production cause an increase in pressure --- hydrocephalusIn newborn or fetus, the fontanels allow this internal pressure to cause expansion of the skull and damage to the brain tissueNeurosurgeon implants a drain shunting the CSF to the veins of the neck or the abdomen14-11Medulla OblongataContinuation of spinal cordAscending sensory tractsDescending motor tractsNuclei of 5 cranial nervesCardiovascular centerforce & rate of heart beatdiameter of blood vesselsRespiratory centermedullary rhythmicity area sets basic rhythm of breathingInformation in & out of cerebellumReflex centers for coughing, sneezing, swallowing etc14-12Ventral Surface of Medulla OblongataVentral surface bulge pyramidslarge motor tractdecussation of most fibersleft cortex controls right musclesOlive = olivary nucleusneurons send input to cerebellumproprioceptive signalsgives precision to movements14-13...
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Tortora - Chapter 14 - The Brain and Cranial Nerves -...

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