Human Biochemistry, Vol. 2 - Murray R. 1993

Biochemistry of Intracellular and Intercellular Communications
Adrenal Medullary Hormones
Introduction

The Autonomic Nervous system comprises the parasympathetic system with cholinergic pre- and postganglionic nerve fibers, the sympathetic nervous system with cholinergic preganglionic and adrenergic postganglionic nerve fibers, and The adrenal medulla. The latter essentially acts as an extension of the sympathetic nervous system, as preganglionic fibers of the splanchnic nerve terminate on chromaffin Cells within the adrenal medulla, which produce catecholamines such as dopamine, norepinephrine, and epinephrine. Consequently, the adrenal medulla Functions as a specialized ganglion lacking axonal projections. The chromaffin cells of this layer synthesize, store, and secrete products whose actions take place far from their site of synthesis. Thus, the adrenal medulla also serves as an endocrine organ—an excellent example of the interaction between the nervous and endocrine systems, as mentioned in Chapter 44.