Imagine your brain as a network of all the airports, airplanes and their flight paths around the world. This network represents the brain cells or neurons and all of their connections. If a storm comes in, some flights will be grounded and others diverted to alternate airport hubs for safety, increasing the operational demand at those hubs. This bad weather also leaves a trail of damage in its path.
The same is true in the brain. A concussion is a bad storm that disrupts many neurons, causes stretching and shearing of the axons, and leads to an overall energy crisis within the brain.
After an injury to the brain, two major events unfold:
1. Activity at the cellular level is disrupted, leading to a loss of potassium ions and an influx of calcium ions. Ion pumps work overtime to return this activity to normal, which requires a lot of energy in the form of glucose.
2. There is a decrease in the blood flow to the brain. However, blood flow is vital to transport much-needed glucose to the injured cells. This results in an energy crisis, where the body needs more glucose but reduced cerebral blood flow prevents its delivery.
Going back to the airport analogy, the storm causes chaos inside the remaining airport hubs as employees become overworked and airports understaffed.
If another bad storm passes through, it can shut down everything. So another head injury during this energy crisis can lead to brain swelling and to a potentially fatal condition called Second Impact Syndrome.