One of the most current and serious health issues today is concussion. You hear about it everywhere from the 4th grade football game to the scene of a fender bender. One of the scariest things about concussion is that it manifests itself in so many different ways– what exactly constitutes a concussion? Does everyone who has a concussion go unconscious? How long until your injury will heal? These questions are nearly impossible to answer because you are dealing with different bodies and different injuries.
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According to the CDC, 1.7 million people suffer from concussions each year.1 Furthermore, they are the cause of 1/3 of all injury-related deaths annually.1 Sports-related concussions are particularly alarming due to their prevalence among adolescents. Per year, it is estimated that 1.6-3.8 million sports related concussions occur in the U.S. to those between the ages of 5 and 18.2 Frighteningly, some hypothesize that at least one mild concussion occurs in every football game played in the U.S.2 While many know that concussions are serious brain injuries, most are still unaware of the biology and chemistry behind these injuries.
What happens?
When the brain goes through some mechanical impact, the first thing that occurs is the opening of K+ channels. Since the cell usually maintains a negative charge within the cell and a positive charge outside the cell, this forces Na+/K+ pumps, the ones which move Na+ out and K+ in, to work overtime.
These channels working overtime is bad news for the cell. The pump needs energy to run, so this forces the cell to try to produce more and more ATP through glycolysis. However, since the brain is always running at its max energy production, this just causes stress on the cell. Additionally, since blood flow decreases in the brain upon injury, the cell doesn’t have much glucose to use to make ATP. Lactate, the endproduct of glycolysis, accumulates in the cell causing swelling and other adverse effects.
Another issue which the mechanical force causes is excitatory neurotransmitter release. Glutamate, the most common excitatory neurotransmitter, binds to its receptors which cause increased Ca2+ levels in the cell. Since Ca2+ in the cell is necessary for neurotransmitter release, this causes further excitation and release of glutamate. Increased Ca2+ also impairs mitochondria, the major players in oxidative metabolism. Of course, this just adds to the decreased energy problem the cell has. Lastly, another imbalance occurs within the cell – lowered Mg2+ levels. This has widespread effects for the cell as Mg2+ is required for so many cellular functions. One of these is energy production.4
The basic story of concussion seems to be a blow to the head and a resulting imbalance of ions and excitation. This leaves your cell scrambling to put everything back in its proper place, which requires a lot of energy – in fact, more energy than the cell can provide in its injured state. Hopefully someday we can find a better way to protect our brains from being knocked around so much, or possibly a chemical treatment to help the cell effectively restore its original balances.
1. http://www.cdc.gov/traumaticbraininjury/
2. http://www.momsteam.com/health-safety/concussion-rates-high-school-sports
3. http://www.womensradio.com/articles/Brain-Injuries%3A-Something-Soldiers-and-Athletes-Have-In-Common/1948.html
4. Giza CC, Hovda DA. The neurometabolic cascade of concussion. Journal of Athletic Training 2001; 36(3): 228-235.
