The brain, through the spinal cord and the nerves, controls every part of the body. In particular, the brain sends messages that control the heartbeat, the movement of the muscles of breathing and all other body functions. Brain cells require a continuous supply of oxygen in order to function, and they are irreversibly damaged if starved of oxygen for more than a few minutes.
Central nervous system
The brain and spinal cord comprise the central nervous system. Messages from the brain are relayed throughout the body via the spinal cord and a complex network of nerve pathways that extends throughout the entire body.
Peripheral nervous system
The peripheral nervous system comprises all the nerves, ganglia (clusters of nerve cell bodies) and sensory receptors outside the central nervous system. It relays impulses from the central nervous system to voluntary muscles (skeletal muscle), and to the autonomic nervous system. This provides the nerve supply to those parts of the body that are not controlled consciously, including the cardiac (heart) muscle and the smooth muscle around blood vessels and the glands of the body.
The peripheral nervous system also relays information back to the brain from the body including sensation, temperature and proprioception (the sense of where parts of the body are in relation to each other).
The breathing control centre
The involuntary urge to breathe is regulated by an area of the brain called the breathing control centre, which is located in the brain stem, close to where the brain joins the spinal cord. To function properly, this control centre must have a good supply of oxygen. Lack of oxygen to the control centre may cause breathing to stop.
Should the airway become blocked for any reason, brain cells will begin to suffer damage due to lack of oxygen. This can rapidly lead to the death of the victim if the airway is not cleared.