Traumatic Brain Injury

There has not always concensus on the classification of the severity of brain injury or in the terms that are used for describing a head injury.  Please describe what is meant by the following terms and how they differ from each other: concussion, mild-traumatic brain injury, post-concussion syndrome (PCS), and dysexecutive syndrome.  You will note that they last two are not described in your book so you will have to search for information on these.