"Chakra" is a Sanskirt word meaning "wheel". A chakra resembles a spinning disc /vortex about the size of a silver dollar that opens and closes like the lens of a camera. Chakras are energy centers that receive and send information and life force energy; neuro-transmitters connecting nerves, hormones and emotions. When a chakra is open it is receiving information (picking up data from the environment around you). Generally speaking whether a chakra is wide open or closed is not as important as whether the chakra system is balanced and the chakras are in alignment with each other.
The seven main chakras are connected to an "energy channel" that runs behind and parallel with the spine. All seven chakras affect each other and are interactive, much like any high-quality, fine-tuned instrument, so it is important that proper balance be maintained.
Each of the seven chakras corresponds with particular body organs and emotional and psychological patterns. Physical illness and disease appear in the etheric body (energy system) prior to manifesting in the physical body. This being the case, I believe that our awareness of and ability to clear out and balance our energy system can be a form of "preventive medicine".