For the purposes of this question, I will use the example of a legally sanctioned athletic contest (i.e., a boxing match), rather than criminal activity or accidents, but the question certainly applies to any brain trauma that has similar effects.
Anyone who watches boxing and other fighting sports knows that when a fighter is hit hard in the head or face, a few things are very likely to happen (links lead to videos showing examples of the effect in question):
The eyes glaze over and seem to lose focus
The fighter will stumble and fall, sometimes after a slight delay
Mobility and coordination are profoundly reduced
In some cases, the fighter will immediately lose consciousness, but I am more interested in the alternative - that is, a serious blow to the brain that results in the above effects, but doesn't render the victim totally unconscious.
Obviously, when the face or head suffers a strong, sudden impact from the front, back, or sides (or, in cases like an uppercut punch, from below, and to the bottom of the chin), momentum causes the brain to strike one or more surfaces inside the skull, so there is some mechanical/physical injury going on - in short, the person who was hit has a concussion. I know that this can cause significant, long-term damage to the brain and nervous system, but I am interested in the short-term, immediate effects.
Is this physical/mechanical injury the sole reason we see the symptoms I've described above? Are there separate processes taking place (e.g., abnormal electrical/chemical activity causing the symptoms described above)? Or does the physical/mechanical injury cause other types of abnormal activity in the brain/nervous system?