Journal article Open Access
Ten mammals and one bird were statistically evaluated, revealing a correlation between the independent variable, cancer risk, and the dependent variables, body weight and the brain-body weight ratio. This was treated in a system of nonhomogeneous differential equations, which graphically show the inclination for said variables and, moreover, the extent of sympathetic activity.
Budgerigars have half the cancer risk of mice, and big mammals are the least susceptible to cancer, possibly because a larger section of their brains is occupied by autonomous centers. These centers, which receive autonomous afferent nerves, are believed to perceive transformed cells that have lost the anchorage to adjacent cells and generated an excess of surface adrenoceptors. This triggers a cascade in the brain, causing extensive noradrenaline discharge from efferent sympathetic fibers in the vicinity of the receptive cell that terminates.