Immediately after a blow to the head, any number of the following: headache, loss of memory, loss of consciousness, confusion, dizziness, nausea or vomiting, etc. Later on, concentration problems, irritability, and sensitivity to light and noise. If you didn’t get hit very hard, some of the symptoms might be subtle.
What’s Going On In There?
In medical terms, a concussion is a mild traumatic brain injury, but in reality there’s nothing mild about it. It’s serious. When you get whacked in the head, the force makes nerves twist and stretch, and your brain hits the inside of your skull.
Read more at http://triathlon.competitor.com/2014/10/training/get-concussion_108061#tKHeCVmGr4JG4mrw.99