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white matter and tracts
mostly myelinated axons
axons are organised into tracts
tracts replay similar info to same destination
ascending tracts - sensory/afferent input to brain
descending tacts - motor/efferent input from brain
gray matter and nuclei
most cell bodies
cell bodies organised into sensory and motor nuclei
sensory nuclei contain cell bodies of interneurons that receive and issue input entering spinal cord
motor nuclei contain cell bodies or motor neurons that receive and issue motor input from brain
protection of brain
nervous tissue = soft and delicate - light pressure can injure neoruns
protected by:
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Blood-brain barrier
protective mechanism
helps provide a stable environment for brain
formed by glial cells (astrocytes) encourage endothelial cells to form tight junctions
↓ permeability
selective permeable
keep metabolic waste, proteins, certain toxins, proteins and most drugs out
blood supply to brain
right and left internal carotid and right vertebral arteries take blood to the cerebrum
arteries form branches to supply the brain
Circle of willies
provides a constant blood supply (the cerebral arterial circle)
unites the anterior and posterior blood supplies
provides alternate routes for blood to reach the cerebrum if a vessel is occluded
provides a constant blood supply to the cerebrum