12.3 Flashcards
Glial cells
-Non neural cells in nervous system that support and protect neurons
-out number neurons by 10-1
-1 trillion in human nervous system
Oligodendrocytes
Form my line sheaths around CNS axons which speed up signal conduction by insulating axon
-type of glial cell
Ependymal cells
Line the internal cavities of the brain, have cilia that help circulate CSF
-type of glial cell
Microglia
-Cleans up debris and responding to injury
-develops from white blood cells and are concentrated on damaged areas
-type of glial cell
Astrocytes
-create supportive framework
-form blood-brain barrier
-regulate blood flow and nutrient supply to neurons
-most abundant glial cell type
Schwann cells
Wrap around axons to form myelin sheaths in the PNS and assist in regeneration of damaged fibers
Satellite cells
Surround neuron cell bodies in ganglia
Provides insulation and regulates chemical environment
Structure of myelin sheath
Insulating layer around axons composed of 20% protein and 80% lipid
When does myelination begin
Begins at 14 weeks of fetal development with dietary fats playing significant role
Do oligodendrocytes form neurilemma in the CNS?
No the myelination process is less efficient leading to different capabilities between CNS and PNS
Outermost layer of myelin sheath in PNS
Neurilemma
When can regeneration of damaged PNS nerve fibers occur
If the soma is intact and some neurilemma remains
What does the regeneration process involve
Degeneration of the axon distal to the injury
Cleanup my macrophages
Formation of regeneration tube by Schwann cells
What does a successful regeneration look like
Reestablishmenf of contact with the original target
Process can take up to 2 years and is not always perfect
Multiple sclerosis
Autoimmune disease where oligodendrocytes and myelins sheaths in the CNS deteriorate
