Nerve heel themselves . However the repair is

Nerve cells are capable of division in the embryonic stages
due to the presence of groth factors, thus if we take out nerve cell from the
stem cells from the embryo and keep it in presence of growth factors, neural
differentiation  may be possible. If differentiated
, these nerve cells can be added to the damaged portion of the body in patients
sufferring from parkinson or mutiple sclerosis, we may be able to regenerate
the damaged nerve cell and the neuron may work functionally.

Neurons are highly efficient in their work, and responsible
for our interaction with the environment. The way we behave, our memory , the
movement of our voluntary muscles are all coordinated by the neurons. Thus they
are the “basic working units of the nervous system”. A nerve cell recieves
information by fine branched thread like structure known as the dendrite. This message
in carried by the axon followed by the cell body with the help of
sodium-potassium ion exchange . the signal is finally transmitted to other
neuron by the nerve ending of the first via a chemical known as the
neurotransmitter or by ion exchange with the help of gap junction. Neve cell
can transmitt information in seconds of receiving the information during reflex
by electrical synapse. However in case of chemical synapse, it takes more time.Nerve
cell which send or receive information from the spinal cord or brain are known
to be central nuerons which play a role mainly during reflexes, memory,
thought, etc while  nerve cells which
pick information from the skin , eye ,etc and deliver information to the
skeletal mucles , etc are refered to as peripheral nerve cells. The central nerve
cells are incapable of regeration primarily because of inavailabity of cells to
fill the damaged portion while in the peripheral nerve cells bridges are formed
by schwann cells  and thus the peripheral
nerve cell can heel themselves . However the repair is not fully efficient and
may only occur if the cell body is intact.  Absence of growth factors which initiate new
growth programs and  inhibition from
neuron supporting cells also leads to the incapability of cell division in
nerve cells.  

Nerve cell or nueron are persistent in our body throughout
life, however if they are damaged or undergo programmed cell death i.e
apoptosis, they do not regenerate . Nerve cell are formed only during the
embryonic stages. And thus when they are damaged or go under apoptosis which
maybe due to environmental condition or due to the gene pool , they may  lead to several diseases such as parkinson’s and
is often fatal.  The diseases caused by
this condition are incurable.