Friday, January 3, 2014

Myelin Sheath and Blood-Brain Barrier

Myelin Sheath

Myelin is a substance that forms the myelin sheath associated with nerve cells.
This sheath is a layer of phospholipids that increases the conductivity of the electrical messages that are sent through the cell.
Diseases such as multiple sclerosis are a result in a lack of this myelin sheath, with the resultant effect being that the conductivity of signals is much slower severely decreasing the effectiveness of the nervous system in sufferers.

Myelinated nerve fibers

A Myelinated nerve fiber is one that is surrounded by a myelin sheath.
The myelin sheath is not part of the neuron but is formed by a supporting cell.

Blood-Brain Barrier

Capillaries in brain do not have pores between adjacent endothelial cells.
        Joined by tight junctions.
Molecules within brain capillaries moved selectively through endothelial cells by:
        Diffusion.
        Active transport.
        Endocytosis.
        Exocytosis.

The nervous system consists of a large number of neurons that are linked together to form functional conducting pathways.
When two neurons come into close proximity and functional interneuronal communication occurs, the site of such communication is referred to as a synapse.
The space between two cells is known as the synaptic cleft.