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.
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