Chapter_9_CNS_1 - Chapter 9 Central Nervous System Chapter...

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Chapter 9 Central Nervous System Chapter Outline CNS: brain and spinal cord Necessary for the maintenance of homeostasis Contains 10 11 neurons (100 billion) Contains 10 14 synapses (100 trillion) Responsible for everything we perceive, do, feel, and think Physical Support of the CNS fig 9.2a Bone Cranium Vertebrae Meninges Dura mater Arachnoid mater Location of blood vessels Pia mater Small thin layer that sits on top of the brain Cerebrospinal fluid Cerebrospinal Fluid (CSF) fig 9.3b Extracellular fluid of the CNS Secreted by Circulates to Reabsorbed by arachnoid villi Replenished Functions Cushions brain Maintains stable interstitial fluid environment SEE TABLE 9.1 Plasma vs CSF Clinical Aspects : Hydrocephalus Blocked drainage 1/500 births corrected by inserting shunt Clinical Aspects: Spinal Meningitis Originates in CSF of subarachnoid space intracranial pressure &/or seizures
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Spinal Tap (Lumbar Puncture) To check CSF for invasion of bacteria or viral particles Needle is inserted into subarachnoid space between the 3 rd th vertebrate Blood Supply to the CNS CNS comprises 2% of body weight (3-4 pounds) Receives 15% of blood supply High metabolic rate Brain uses 20% of oxygen consumed by body at rest Brain uses 50% of glucose consumed by body at rest Depends on blood flow for energy High Demand for Blood Depends on aerobic glycolysis Requires glucose and oxygen No glycogen stores Fatty acids not used for energy Ketones used during extreme conditions Clinical Aspects:Strokes Caused by decreased blood supply Occlusion of cerebral blood vessel (carotid artery) Hemorrhage from cerebral blood vessel FAST : Face Arm Speech Test ABCMH A Aphasia (in left side lesions) B Blindness (unilateral) C Coma, Convulsions M Mentality changes H ICH (intracerebral hemorrhage) Physical causes: skull fracture, violent shaking, sudden accelerative force Risks: age, hypertension, African Amercian and Males Most die in first 2 days; fewer than 20% live independently at 6 months Signs: vomiting, headache, ↑ BP Gray Matter and White Matter fig 9.5a
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Chapter_9_CNS_1 - Chapter 9 Central Nervous System Chapter...

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