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How is the CNS protected from Injuries?

How is the CNS protected from Injuries?. 1. The Meninges. Composed of 3 Connective Tissue Membranes 1. Dura Mater – “Tough Mother” outer layer of protection that covers and protects the brain A. Falix Cerbri - extension of the dura mater that separates the two hemispheres of the cerebrum.

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How is the CNS protected from Injuries?

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  1. How is the CNS protected from Injuries?

  2. 1. The Meninges • Composed of 3 Connective Tissue Membranes • 1. Dura Mater – “Tough Mother” outer layer of protection that covers and protects the brain • A. FalixCerbri- extension of the dura mater that separates the two hemispheres of the cerebrum

  3. Meninges Continued • B. TenoriumCerebelli- extension of the dura mater that separates the cerebrum from the cerebellum • C. FalxCerebelli- separates the two hemispheres of the cerebellum

  4. Meninges Cont. • 2. Arachnoid Mater- middle layer of the meningies • Threadlike layer that looks like spider webs through the entire surface • Creates an open space where CSF can circulate

  5. 3. Pia Mater • Innermost meningeal layer • Clings to the surface of the brain and spinal cord • Arachnoid villi project up into the arachnoid layer from here and re-absorb CSF to maintain a steady pressure within the meningeal space

  6. CSF • Water based cushioning fluid • Formed by the choroid plexus of each lateral ventricle (networks of capillaries within the walls of the ventricles) • Formed by blood plasma

  7. Circulation of CSF • Flows from choroid plexus to the third ventricle • More CSF is added at the 3rd ventricle and it moves through the cerebral aqueduct through the midbrain and onto the 4th ventricle • Choroid plexus here adds more CSF and it enters the subarachnoid space • From here it circulates into the central canal of the spinal cord, through the subarachnoid space around the brain • Pressure is 150 mL per vol • Spinal tap is used to check it for infection

  8. Blood-Brain Barrier • Maintains a constant internal environment for the brain • Tight junctions seal together the endothelial cells of the brain capillaries preventing free passage of substances • Glucose passes via active transport • Creatinine, Urea, and ions cross slowly • Proteins and antibiotic drugs do not pass at all • This barrier is useless against fat-soluble substances • So, Oxygen, Carbon Dioxide, alcohol, and fat-soluble drugs all pass freely

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