Axons carry signals to and from the neurons and are covered by a protective sheath called myelin. Axons are metabolically independent from neurons so that if an axon is injured, its function will be disrupted even though the neuron may still be intact. Like most parts of the brain, the spinal cord is over-designed, Ransom said. We may have lost some, but if we can get the residual axons to work better, there can be some improvement. A traumatic injury can tear an axon apart, or, more commonly, it can damage an axon by producing reduced blood flow.
Blood supplies the axon with the oxygen and glucose it needs to function.
Studies done in the 1940s demonstrated that brain cells stop working 6-8 seconds after their blood supply is cut off. After five minutes, irreversible neuron damage occurs. In order to be able to minimize damage, it is important to understand what causes nerve cell damage after the restriction of oxygen and glucose, he said. When glucose and oxygen are cut off, ATP production stops, disrupting the orderly balance of ions in the cells. Calcium, normally only present between cells, rushes inside the cells, and activates enzymes that destroy cell membranes and proteins.