Role of Myelination and Multiple sclerosis Flashcards
What is the structure/ anatomy of myelination?
Myelin is fatty tissue that wraps around neuron axons
Myelination is performed by 2 glial cells- Schwann cells and oligodendrocytes.
Schwann cells wrap individual axons- myelination in the PNS
oligodendrocytes (cns) wraps several axons
What is a node of Ranvier?
it is a naked axon- so it is not insulated by myelin.
purpose of myelin
When areas are insulated there is no ion leakage meaning AP can spread a further distance. AP is only triggered at each node of Ranvier as ions can only cross membrane at nodes of Ranvier. This means an action potential can move quickly along an axon by jumping from node to node. This is called SALATORY CONDUCTION.
How is myelin economic?
Sodium enters during action potential.
this sodium must be removed via sodium potassium pump.
so myelinated areas stop lots of sodium entering as they can only enter at nodes of Ranvier meaning less enters so less to be removed.
So overall myelin saves ATP as less energy is required by the cell to pump out the sodium.
What is multiple sclerosis
disorder of thCNS
Immune system attacks myelin sheaths leaving behind sclerotic plaques. This means normal transmission of neural messages is interrupted.
Symptoms of multiple sclerosis
all due to damage of white matter
fatigue numbness' visual issues tingling paralysis
treatments to multiple sclerosis
Interferon B and Glatiramer acetate are both partially effective treatments. GA is a mixture of synthetic peptides and it was found it reduces symptoms. They are only effective for remitting-relapsing form of MS and not the progressive form. Ga works by stimulating certain cells of immune system to to secrete anti inflammatory chemicals which prevents activity of immune cells which would be attacking myeline. / another encouraging treatment is transplanting autologous hemopoietic stem cells
