A concussion may occur from a direct blow to the head, face or neck. This may be a punch, fast moving object such as a baseball, or a clash of body parts such as head-to-head or head-to-knee. A concussion can can occur from collisions between Athletes or the head striking the ground. Indirect trauma can also cause a concussion including whiplash-type jerking movement of the head and neck.
The force to the head, neck or other portion of the body results in the brain shifting inside the skull and knocking against the inner bony surface. This may be enough to cause microscopic shearing of nerve fibers and probably sets off a process of swelling and a series of chemical reactions that affects the way the brain works (e.g. thinking and co-ordination).