Learning Modules - Medical Gross Anatomy
Introduction to Autonomics, Part 2 - Page 5 of 12


The suprarenal gland (also known as the adrenal gland) is unique in its innervation and function. The cells in the medulla of the suprarenal gland behave like a collection of postsynaptic sympathetic neurons in that they release epinephrine (and some norepinephrine) upon stimulation by a presynaptic sympathetic nerve. Presynaptic sympathetic fibers to the suprarenal medulla pass from the greater thoracic splanchnic nerves through the celiac ganglia without synapsing and terminate on the medullary cells. In response to the presynaptic signal, the suprarenal medullary cells release epinephrine (and norepinephrine) into the blood stream. In contrast to postsynaptic sympathetic neurons that release norepinephrine onto specific organs resulting in a change of function within that organ, the cells of the suprarenal medulla secrete epinephrine (85%) and norepinephrine (15%) into the blood stream producing a systemic, or whole-body, fight or flight response.

Go to Question