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 Nerves•Largest organ in the body at almost 3 lb.•Brain functions in sensations, memory, emotions, decision making, behavior14-2Principal Parts of the Brain•Cerebrum•Diencephalon–thalamus & hypothalamus•Cerebellum•Brainstem–medulla, pons & midbrain14-3Protective Coverings of the Brain•Bone, meninges & fluid•Meninges same as around the spinal cord–dura mater–arachnoid mater–pia mater•Dura mater extensions–falx cerebri–tentorium cerebelli–falx cerebelli14-4Blood Supply to Brain•Arterial blood supply is branches from circle of Willis on base of brain (page 699)•Vessels on surface of brain----penetrate tissue•Uses 20% of our bodies oxygen & glucose needs–blood flow to an area increases with activity in that area–deprivation of O2 for 4 min does permanent injury•at that time, lysosome release enzymes•Blood-brain barrier (BBB)–protects cells from some toxins and pathogens•proteins & antibiotics can not pass but alcohol & anesthetics do–tight 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, & ions•Functions–mechanical protection •floats brain & softens impact with bony walls–chemical protection•optimal ionic concentrations for action potentials–circulation•nutrients and waste products to and from bloodstream14-6Origin of CSF•Choroid plexus = capillaries covered by ependymal cells–2 lateral ventricles, one within each cerebral hemisphere–roof of 3rd ventricle–fourth ventricle14-7Drainage of CSF from Ventricles•One median aperture & two lateral apertures allow CSF to exit from the interior of the brain14-8Flow of Cerebrospinal Fluid14-9Reabsorption of CSF•Reabsorbed through arachnoid villi–grapelike clusters of arachnoid penetrate dural venous sinus•20 ml/hour reabsorption rate = same as production rate14-10Hydrocephalus•Blockage of drainage of CSF (tumor, inflammation, developmental malformation, meningitis, hemorrhage or injury•Continued production cause an increase in pressure --- hydrocephalus•In newborn or fetus, the fontanels allow this internal pressure to cause expansion of the skull and damage to the brain tissue•Neurosurgeon implants a drain shunting the CSF to the veins of the neck or the abdomen14-11Medulla Oblongata•Continuation of spinal cord•Ascending sensory tracts•Descending motor tracts•Nuclei of 5 cranial nerves•Cardiovascular center–force & rate of heart beat–diameter of blood vessels•Respiratory center–medullary rhythmicity area sets basic rhythm of breathing•Information in & out of cerebellum•Reflex centers for coughing, sneezing, swallowing etc14-12Ventral Surface of Medulla Oblongata•Ventral surface bulge –pyramids–large motor tract–decussation of most fibers•left cortex controls right muscles•Olive = olivary nucleus–neurons send input to cerebellum–proprioceptive signals–gives precision to movements14-13...
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Tortora - Chapter 14 - The Brain and Cranial Nerves -...

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