Sagittal slice from a MRI scan of a human brain. See an animated sequence of slices.

The nervous and endocrine systems facillitate integration of cellular processes to achieve physiological coordination. Both systems employ signals to bring about changes in effector organ processes. The traditional distinction between nervous system action (fast nerve impulse) and endocrine system action (slow hormones), has become blurred over the past few decades of research. For example, the nervous system employs many local hormones to modulate neuron activity. Many activities of the nervous and endocrine systems are tightly integrated.