Baroreceptor and Chemoreceptor Reflexes
Afferent (green) nerves carry action potentials from sensory receptors to the medulla oblongata.  Sympathetic (blue) and parasympathetic (red) nerves exit the spinal cord or medulla and extend to the heart to regulate its function.  Hormonal influences such as epinephrine and norepinephrine from the adrenal gland also help regulate the heart's action.