An Introduction to Neuroendocrine Systems

This chapter introduces the science of neuroendocrinology, offering general descriptions of neuroendocrine systems. Neuroendocrinology is a relatively new science that emerged in the mid-20th century as a branch of endocrinology, propelled in part by the realization that the brain produces neurohormones and thereby functions as an endocrine organ. Homeostatic regulation in physiological systems can be described in terms of control systems analysis, using basic terms and concepts borrowed from engineers. Neuroendocrine homeostatic systems can involve the hypothalamus, anterior pituitary, and an end-organ or target tissues functioning together as an axis. Secretions of GH and PRL are predominantly under the control of two-tier systems in which short-loop feedback functions are the major regulatory mechanism. The reduced importance of long-loop feedback control in these systems is probably a function of the distributed targets of GH and PRL actions. A fundamental property that is specific to many neuroendocrine cell groups is the propensity to release neurohormone in synchrony and at regular intervals.