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Blood-Brain Barrier

Topic updated on 03/20/17 9:11pm

Overview
 
                                  
 
Snapshot
  • A 56-year-old female is brought to the emergency department by her daughter due to new-onset abnormal movements suggestive of a seizure. While the patient is being managed, the physician learns that the patient is being treated for lung cancer. Head CT was obtained after the patient was stabilized.
Introduction
  • Structure 
    • tight junctions between nonfenestrated capillary endothelial cells
      • also consists of astrocytic foot processes, pericytes, basement membrane
    • irradiation, malignancy, infection can disrupt the blood-brain barrier (BBB)
      • infarction destroys tight junctions → vasogenic edema
        • fluid is extravasated into the interstitial space
  • Function
    • control entry of substances into the brain
      • substances cross via diffusion, ion channels, and selective transport proteins
        • diffusion: nonpolar/lipid-soluble substances readily cross the BBB
          • O2, CO2, heroin, nicotine
        • ion channels: movement of Na+ and K+
        • selective transport proteins: nutrients
          • glucose, amino acids, peptides
          • removes metabolites
    • certain areas of the CNS lack a BBB
      • posterior pituitary (neurohypophysis)
        • allows ADH release from brain into systemic circulation
      • area postrema
        • chemotherapeutic drugs → vomiting
      • vascular organ of the lamina terminalis (OVLT)
        • senses blood osmolality


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