Why can't nerves be replaced?

Well, neurogenesis does occur in the subventricular zone of the anterior lateral ventricles and the dentate gyrus of the hippocampus, despite previous claims that it does not. I'm assuming that you are referring to a massive loss of neurons, though. read more

The human brain and spinal cord contain approximately 100 billion nerve cells. They are the only cells in the human body that do not regenerate. For example, human skin, liver and heart cells regenerate at a high rate. read more

This is possible because in the Peripheral Nervous System, we have a special cell called a Schwann cell which forms a tunnel around the nerves. After a nerve has been cut, the Schwann cell tunnel remains as a guide for the newly regrowing nerve to travel. read more