The top two vertebrae in the spinal column surround the lower brain stem. These two bones are the most freely moveable vertebrae of the entire spine. They allow us to turn our head from side to side, look up and around, and move in three directions (unlike the two directions in which all other vertebrae move). Due to the amount of mobility here, we give up stability making these bones prone to misalignment. When one of these bones misalign, it exerts an irritation onto the lower brain stem interfering with the nerve impulses traveling from the brain to the body and back again.
Adjustments, or manipulation as they're sometimes referred to, is the minor movement of vertebrae in the spine. The objective of this movement is to realign vertebrae that have moved out of place for a number of reasons ranging from normal daily activity to trauma such as a car accident.
When these vertebrae are out of place, it has an overall systemic effect from muscular to the central nervous system. Without proper alignment and flow of all nerves and systems in the body from the brain, we can't function at our peak.
An adjustment is often a pressure from the chiropractor utilizing the hands or an instrument to move a vertebrae back into place. This happens with a quick movement and is often without discomfort. You may hear a noise that sounds like you're cracking your knuckles referred to as joint cavitation. It is the release of gases such as oxygen and nitrogen from the joint.
Overall, adjustments are an excellent way to keep the body functioning at its highest level. When the body is in alignment, the body is able to respond and perform as it was designed to.