Y2 s1 csf

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Y2 s1 csf

  1. 1. cerebrospinal fluid (CSF) Prof. Vajira Weerasinghe Dept of Physiology
  2. 2. cerebral blood flow <ul><li>750 ml/min (15% of cardiac output) </li></ul>
  3. 3. cerebrospinal fluid <ul><li>The cavity enclosing the brain & spinal cord, and the central canal: filled with CSF </li></ul><ul><li>This fluid is in </li></ul><ul><ul><li>ventricles </li></ul></ul><ul><ul><li>cisterns </li></ul></ul><ul><ul><li>subarachnoid space </li></ul></ul><ul><ul><li>central canal </li></ul></ul>
  4. 5. cushioning function <ul><li>brain is floating in the fluid </li></ul><ul><li>this provides a protective function </li></ul>
  5. 6. contrecoup injury <ul><li>when there is a severe blow on the head </li></ul><ul><li>brain is lushed so that the opposite side is struk on the skull to cause an injury </li></ul>
  6. 7. <ul><li>volume of CSF </li></ul><ul><ul><li>150 ml </li></ul></ul><ul><li>rate of production </li></ul><ul><ul><li>500 ml/day </li></ul></ul><ul><li>formed </li></ul><ul><ul><li>mainly in the choroid plexuses of the ventricles </li></ul></ul><ul><ul><li>small amounts in the ventricles, arachnoid membranes & perivascular spaces </li></ul></ul>
  7. 9. formation <ul><li>choroid plexus projects into </li></ul><ul><ul><li>horn of lateral ventricle </li></ul></ul><ul><ul><li>posterior portion of 3rd ventricle </li></ul></ul><ul><ul><li>roof of the 4th ventricle </li></ul></ul><ul><li>Mechanism: </li></ul><ul><ul><li>active transport of Na through the epithelial cells, Cl follows passively </li></ul></ul><ul><ul><li>osmotic outflow of water </li></ul></ul><ul><ul><li>glucose moves in to CSF </li></ul></ul><ul><ul><li>K and HCO3 moved out of CSF </li></ul></ul>
  8. 10. absorption <ul><li>arachnoid villi in the walls of venous sinuses </li></ul>
  9. 11. circulation <ul><li>fluid secreted in the lateral ventricles into the 3rd ventricle (secretes here) </li></ul><ul><li>pass along the aqueduct of Sylvius into the 4th ventricle </li></ul><ul><li>through foramina of Luschka & Magendie into the cisterna magna (behind the medulla) </li></ul><ul><li>subarachnoid spaces around the brain & spinal cord </li></ul><ul><li>arachnoid villi in the venous sinuses </li></ul>
  10. 15. composition <ul><li>similar to plasma </li></ul><ul><ul><ul><ul><li>CSF Plasma </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Na 147 (similar) 150 mmol/l </li></ul></ul></ul></ul><ul><ul><ul><ul><li>K 2.9 (less) 4.6 mmol/l </li></ul></ul></ul></ul><ul><ul><ul><ul><li>HCO3 25 24.8 mmol/l </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Cl 113 (more) 99 mmol/l </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Pco2 50 40 mmHg </li></ul></ul></ul></ul><ul><ul><ul><ul><li>pH 7.33 7.4 </li></ul></ul></ul></ul><ul><ul><ul><ul><li>osmolality 289 (similar) 289 mosm </li></ul></ul></ul></ul><ul><ul><ul><ul><li>protein 20 (less) 6000 mg/dl </li></ul></ul></ul></ul><ul><ul><ul><ul><li>glucose 64 (less) 100 mg/dl </li></ul></ul></ul></ul><ul><ul><ul><ul><li>urea 12 (less) 15 mg/dl </li></ul></ul></ul></ul><ul><li>some substances do not pass into CSF </li></ul>
  11. 16. blood brain barrier <ul><li>tight junctions between capillary endothelial cells & epithelial cells in the choroid prevent some substances entering CSF </li></ul><ul><li>small molecules & lipid soluble substances pass through easily </li></ul><ul><li>blood-brain barrier exists between blood & brain tissue </li></ul><ul><li>blood-CSF barrier is present in choroid </li></ul><ul><li>these barriers are </li></ul><ul><ul><li>highly permeable to water, CO 2 , O 2 , lipid soluble substances (such as alcohol), most anaesthetics, </li></ul></ul><ul><ul><li>slightly permeable to electrolytes </li></ul></ul><ul><ul><li>impermeable to proteins, large organic molecules </li></ul></ul><ul><ul><li>drugs (variable) </li></ul></ul>
  12. 17. Blood brain barrier
  13. 18. blood brain barrier <ul><ul><ul><li>CO 2 & O 2 crosses easily </li></ul></ul></ul><ul><ul><ul><li>H+ & HCO3- slow penetration </li></ul></ul></ul><ul><ul><ul><li>glucose </li></ul></ul></ul><ul><ul><ul><ul><li>passive: slow penetration </li></ul></ul></ul></ul><ul><ul><ul><ul><li>active transport system by glucose transporter GLUT </li></ul></ul></ul></ul><ul><ul><ul><li>Na-K-Cl transporter </li></ul></ul></ul><ul><ul><ul><li>transporters for other substances </li></ul></ul></ul>
  14. 19. blood brain barrier <ul><ul><li>No blood brain barrier in the hypothalamus & posterior pituitary </li></ul></ul><ul><ul><ul><li>substances diffuses easily </li></ul></ul></ul><ul><ul><ul><li>these areas contain chemoreceptors for various substances to detect changes in conc </li></ul></ul></ul>
  15. 20. CSF pressure <ul><li>lumbar CSF pressure: 70-180 mmH 2 O </li></ul><ul><li>this is regulated by absorption through arachnoid villi </li></ul><ul><li>rate of CSF formation is constant </li></ul>
  16. 21. CSF pressure rises <ul><ul><li>if the arachnoid villi are blocked by a disease process </li></ul></ul><ul><ul><li>brain tumour may compresses the brain and blocks the absorption </li></ul></ul><ul><ul><li>haemorrhage into the brain tissue can block small channels in the arachnoid villi </li></ul></ul><ul><ul><li>babies are born with high CSF (as in hydrocephalus) due to a defect before birth </li></ul></ul><ul><ul><ul><li>blocking the aqueduct of Sylvius </li></ul></ul></ul><ul><ul><ul><li>blocking of arachnoid villi </li></ul></ul></ul>
  17. 25. cerebral oedema <ul><ul><li>because brain is enclosed in a solid cranial vault, accumulation of fluid compresses brain tissue and have serious effects </li></ul></ul><ul><ul><li>happens due to increased capillary pressure or damage to the capillaries </li></ul></ul><ul><ul><li>causes </li></ul></ul><ul><ul><ul><li>compresses vasculature, decreases blood flow, brain ischaemia, arteriolar dilatation, increased capillary pressure, oedema worsens </li></ul></ul></ul><ul><ul><ul><li>decreases blood flow, deceases oxygen supply, increases capillary permeability, more fluid leakage </li></ul></ul></ul>
  18. 26. Cerebral oedema <ul><li>A 45-year-old man was brought to the emergency department by his friends </li></ul><ul><li>because of a 1-day history of a severe headache and &quot;bizarre behavior.“ </li></ul><ul><li>CT scan of his brain revealed </li></ul><ul><ul><li>acute intracranial hemorrhage </li></ul></ul><ul><ul><li>with cerebral edema </li></ul></ul><ul><ul><li>evidence of midline shift </li></ul></ul><ul><ul><li>increased intracranial pressure </li></ul></ul><ul><li>The patient was admitted to the intensive care unit (ICU) </li></ul><ul><li>young patient </li></ul><ul><li>was found belatedly after a collapse </li></ul><ul><li>secondary to drug overdose </li></ul><ul><li>Note the extensive cerebral oedema </li></ul><ul><li>with loss of normal grey-white matter differentiation. </li></ul><ul><li>The patient never regained consciousness </li></ul><ul><li>eventually died with increased intracranial pressure. </li></ul>
  19. 27. brain metabolism <ul><li>brain metabolism is 15% of total metabolism of the body (although brain mass is 2% of total body mass) </li></ul><ul><li>therefore brain has an increased metabolic rate </li></ul><ul><li>this is due to increased activity of neurons (AP) </li></ul><ul><li>requires oxygen </li></ul><ul><li>brain is not capable of anaerobic metabolism </li></ul><ul><li>energy supply is by glucose </li></ul><ul><li>glucose entry is not controlled by insulin </li></ul>
  20. 28. Lumbar puncture <ul><li>This is the method of obtaining access to the subarachnoid space This is done for the following purposes </li></ul><ul><ul><li>To obtain CSF for examination </li></ul></ul><ul><ul><li>To estimate CSF pressure </li></ul></ul><ul><li>Patient lying on one side </li></ul><ul><li>LP needle is inserted between 3 rd and 4 th or 4 th and 5 th lumbar spinous processes </li></ul><ul><li>Fluid is withdrawn </li></ul><ul><li>Manometer is connected and pressure measured </li></ul>
  21. 29. Lumbar puncture

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