Myelin and myelination - oligodendrocytes and Schwann cells Flashcards
What is the main function of myelin?
To allow fast and efficient transmission of impulses along the axons.
(facilitate action potential transmission)
At what stage of development, does myelination start? When does it end?
Myelination starts late in development, just a little bit before birth.
It ends late, up to 30 years later.
What is the psychological impact of myelination?
Better judgement, impulse control, decision making, social interactions
What area of the brain is the first to be myelinated?
Myelination starts in the spinal chord.
What cells are responsible for myelination?
Schwann cells and oligodendrocytes
What is the node of ranvier? What is its function?
The area of the axon with no myelination (the gaps).
The nodes of ranvier, have Na+ channels, and are boosters: they are able to enhance the modes of transmission (saltatory transduction)
What is saltatory transduction?
The nodes of ranvier, have Na+ channels, and are boosters: they are able to enhance the modes of transmission.
Depolarization happens one node after another - the positive current moves to the next node, where membrane pumps will cause another depolarization, and this continues to move down the axon. After they are retuned to the normal action potential.
How is myelin function connected to motor skills?
Animals will be worse at learning motor skills, if myelin development and maintenance is deficient
What is the main difference between oligodendrocytes and schwann cells?
Oligodendrocytes: CNS, multiple areas and cells.
Schwann cells: PNS, one cell one area.
What determines how much myelin is on an axon?
Its size - the thickness of myelination is proportional to the axon diameter.
Smaller axons may not be myelinated.
What signal suppress oligodendrocyte fate in progenitors to create neurons?
BMP signaling
Where do oligodendrocyte progenitors first arise?
From the pMN region of the neural tube
How do myelin sheaths form?
The sheath moved both around and out. The cytoplasmic channels allow for transport of materials needed for growth.
Where do schwann cells progenitors first arise?
Schwann cells are generated from the neural crest (the area on top of the neural tube)
Why is schwann cell plasticity important for axonal regrowth?
Schwann cells are able to return to an immature stage and help guide the growing axon.
