Heart rate, breathing rate and the diameter of blood vessels are controlled by the

Explanation

The medulla lies at the top of the spinal cord and contains the cardiac, respiratory and vasomotor centres, all of which work without conscious control, so an injury there is very quickly fatal. Because these centres monitor carbon dioxide and blood pressure and correct them, the medulla is a key homeostatic organ. The corpus callosum is only the bundle of fibres joining the two cerebral hemispheres.