This is what happens when our brain hits our skull. DYSFUNCTION AND STRESS. Our nerves go through microstructural damage by sheering or stretching. What does it mean to stretch a nerve? Disruption to blood flow, ion channels, and neurotransmitters. All those important elements we just talked about that help us function.
Disruption of Blood Flow
When blood vessels are broken or damaged, the brain is not supplied with adequate blood flow. If we have a reduction of blood flow, it means we have a reduction of oxygen being transported to the brain. Lack of oxygen leads dysfunction and takes longer for us to heal since oxygen is a key element to promote healing.
Disruption of Neurotransmitters
When nerves are initially damaged, there tends to be a massive release of excitatory neurotransmitters, like glutamine. The release of glutamine triggers the influx of positive ions from the extracellular membrane, like Na+ and Ca+ ions. Why is this bad? Increase in glutamine, influx of Ca+ and Na+ moving into the intracellular membrane which directly affects the function of the Na+/K+ pump and restoring resting potential. Remember, another action potential will not be able to fire if the neuron does not stabilize by cycling through its refractory period. On a bigger scale, this means there will be delayed or lost messages from the brain or body. Furthermore, the accumulation of Ca+ can impair ATP production in the mitochondria* and can lead to cell death.
Disruption of Na+/K+ Pump
We spoke about the importance of the Na+/K+ pump in regards to maintaining resting potential in neurons. With the influx of positive ions in the membrane, the Na+/K+ pump is working overtime to try and restore resting potential. We know that ATP powers the pump. Thus, if the pump is working harder, ATP supply needs to be greater. Our body does everything it possibly can to try and supply these pumps with energy, however the supply has trouble keeping up with the demand (mitochondria dysfunction) which leads to an energy crisis. Ever wonder why you are super fatigued all the time after the initial concussion? A lot of our energy is going towards stabilizing and fixing our dysfunctional neurons and vessels.
All these changes happen within seconds, but can last up to weeks or months to recover. For example, the massive influx of excitatory neurotransmitters stabilizes within minutes, but proper blood flow is usually not restored until 10-14 days after the initial blow. That's why it's so important to start aerobic rehab within a few days of hitting your head. It promotes healing of damaged blood vessels and leads to the creation of others to restore proper blood flow to the brain.
This also brings into perspective how you need to have a structured plan to return to sport or work after the initial hit. Even if you feel 'fine' within a few days, the body needs time for the metabolic changes to subside. Going back to 'normal' too soon, can delay the recovery time and make symptoms worse. Furthermore, it can also lead to Post Concussion Syndrome, the very scary reality that your symptoms become chronic.
Everyone's recovery time looks different. Children, adults, people with predisposed health conditions will all experience a concussion differently. Why? Because brains are complicated. So it's important to find concussion rehab help right away, be patient, and listen to your body. If you are in a position to start rehab within the first 48-72 hours, do it! It is crucial to kickstart recovery and increase your chances of improving symptoms quicker.
References
Crash Course (2014). The Chemical Mind: Crash Course Psychology #3. [Video]. YouTube. https://www.youtube.com/watch?v=W4N-7AlzK7s
Giza, C. C., & Hovda, D. A. (2001). The Neurometabolic Cascade of Concussion. Journal of athletic training, 36(3), 228–235.
Sahyouni, R., Gutierrez, P., Gold, E., Robertson, R. T., & Cummings, B. J. (2017). Effects of concussion on the blood-brain barrier in humans and rodents. Journal of concussion, 1, 10.1177/2059700216684518. https://doi.org/10.1177/2059700216684518
Speed Pharmacology (2016). Neuron Action Potential (Made Easy). [Video] YouTube. https://www.youtube.com/watch?v=XnksofQN8_s
Rehab Lab (2022, March 7). Day 1 Concussion Recovery Bootcamp. [Video] YouTube. https://www.youtube.com/watch?v=gOxNefEGUv8