cerebrospinal fluid and blood-brain barrier

CSF

• similar to blood plasma composition

• formed by the choroid plexus

  • choroid plexuses-capillaries in the ventricles of the brain

• forms a watery cushion to protect the brain

• circulated in the arachnoid space, ventricles and central canal of the spinal cord

• CSF carries antibodies

• constant pumping mechanism that goes through the entire brain, the brain stem, the spinal cord, all the way to sacrum

CSF pathway of flow

1.) CSF is produced by the choroid plexus of each ventricle

2.) CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. some CSF flows through the central canal of the spinal cord

3.) CSF flows through the subarachnoid space

4.) CSF is absorbed into the sural venous sinuses via the arachnoid villi

hydrocephalus in a newborn

• CSF accumulates and exerts pressure on the brain if not allowed to drain and reabsorb properly

• possible in an infant because the skull bones have not yet fused

  • starts expanding, pushing outward, resembling a lightbulb

  • common in NICU

• in adults, this situation results in brain damage

  • exerting pressure on brain, causing neurons to die

blood-brain barrier

• astrocytes

• includes the least permeable capillaries of the body

• excludes many potentially harmful substances

• useless as a barrier against some substances

  • fats and fat soluble molecules (because of myelin, which is made of fat)

  • respiratory gases (such as O2)

  • alcohol

  • nicotine

  • anesthesia