Nerve regeneration in the peripheral nervous system
© LifeArt / Super Anatomy 3
Unlike nerves in the brain and spinal cord (central nervous system) can
the nerve cells, which are outside thereof (peripheral nervous system), according to
completely regenerate damage to some degree.
Using nerve cells of the body can receive stimuli in the form of electrical
forward pulses and transmit such signals to the brain. Tree-like outgrowths
(So-called. Dendrites) of the nerve cell to take the stimuli, pass them through the
Cell body and from there toward Axon.
Each nerve cell has usually only a single axon - a long,
tubular cell process, which in conjunction with the dendrite of another
Nerve cell is. Some axons are of myelin surrounded a kind
electrical insulating layer also provides some mechanical protection. The
Myelin is formed by the so-called Schwann cells, which is why the myelin sheath
sometimes too "Schwann sheath" lists. Axons with myelin sheath can significantly stimuli
conduct faster than the "uninsulated" Axons.
The cell far end of the axon has no direct contact to the neighboring nerve cell,
but is a so-called synapse indirectly associated with it. reaches
the stimulus from the cell body eventually to the cell distal end of the axon, be
chemical messengers (Neurotransmitters) distributed. this cross
a gap - the synaptic cleft - and dock onto receptors of the
Neighboring nerve cell to, which in turn triggers an electrical pulse
axons can damage Take, for example, by disease or injury
- and thereby also the nerve cells. As a result, it can cause pain or
Sensory disturbances (such as tingling, numbness and similar
Paresthesia) may occur. Under certain conditions, nerve cells can
However, in the peripheral nervous system regenerate and their old function very
or partially resume.
Whether this works depends mainly on the type of axonal damage, and whether
the cell body of the nerve cell is undamaged. On average start
To regenerate nerve cells about two to three days after the injury so that
and the axon grows - about 0.5 to 3 millimeters per day. Under
favorable conditions, it is possible in the peripheral nervous system that in a
damaged body portion (depending on the extent of damage) within weeks or
Axons months - and in nerve fibers - regenerate.
The nerve regeneration begins in each case at the point where the axon
was severed or damaged. disintegrate Axonreste behind the breaking point, which
remaining cell residues by the macrophages of the body (macrophages)
To repair the defect after axonal damage, the nerve cell begins
highly produce new proteins, as a replacement for the lost cell material
to serve. The Axonstumpf widens the so-called "growth piston", there
from the cell body new cell material is delivered and accumulates.
From the point of contact with the axon of the neuron was formerly attached form
the remaining Schwann cells a kind Guardrail and enter along with other
Cell proteins from which the growth factor act. Proteins serve as
Attractant for renewable Axon: The Axonstumpf restarts auszusprossen
and growing by the guide rail in the direction.
Once the axon reaches the previous contact point form again synapses
and the Schwann cells wrap around the regrown Axonabschnitte with myelin. The
Myelin sheath at regrown axons is generally thinner than before