The large, ovoid opening at the base of the skull, measuring about 3 x 3.5cm, through which the The main nerve trunk running down the spinal canal and connecting the individual’s mind and consciousness to the rest of his or her body. It is about the size of a person’s little finger, in diameter. It cannot repair itself if damaged. passes, to continue on as the This is the most primitive part of the brain, connecting the rest of the brain to the body, via the spinal cord. In addition to feeding signals to and from such “higher centres”, the brain stem contains a number of important control centres, regulating vital functions such as breathing and blood pressure..