Can neurons be replaced if damaged?

As a neuroscientist with a focus on cellular and molecular neuroscience, I can provide insight into the complex nature of neuronal repair and regeneration. The human body has a remarkable capacity for healing and regeneration in many of its tissues. However, the neurons in our brain and nervous system are unique in that they are post-mitotic, meaning they do not undergo cell division to produce new cells. When neurons are damaged, the body's ability to repair them is limited. Unlike skin or bone, which can heal by replacing damaged cells with new ones, damaged neurons typically cannot be replaced. Instead, the body relies on the remaining healthy neurons to compensate for the loss of function. In some cases, neurons can repair themselves, particularly in the case of minor injuries. For instance, if the axon of a neuron is injured, the neuron may be able to repair or even fully regenerate its axon, depending on the severity of the damage and the location within the nervous system. However, this regenerative capacity is not universal across all types of neurons or all parts of the nervous system. The central nervous system (CNS), which includes the brain and spinal cord, has a much lower capacity for regeneration compared to the peripheral nervous system (PNS), which is the network of nerves outside the CNS. In summary, while there is some capacity for neuronal repair, the ability to replace damaged neurons is limited and varies depending on the type of injury and the location within the nervous system.

Other parts of your body -- such as skin and bone -- can be replaced by the body growing new cells, but when you injure your neurons, you can't just grow new ones; instead, the existing cells have to repair themselves. In the case of axon injury, the neuron is able to repair or sometimes even fully regenerate its axon.