Neuroendocrine networks in the brain are interconnected circuits of neurons, forming the central components of neuroendocrine control systems, and, in some cases, extending into the spinal cord. Their activity organizes behaviors and desires, autonomic nervous action, and the activity of endocrine systems. Neuroendocrinology is the study of how the brain controls body function by regulating the secretion of hormones, and includes study of the actions of hormones on the brain. Almost all of the endocrine glands are controlled by the brain, and almost all hormones can affect (by “feedback”) brain activity. The hypothalamus is the major neuroendocrine part of the brain, but it has important connections with brain regions concerned with monitoring the internal and external environments, and in the generation of emotion and behaviors.