文档介绍：Chapter 12
The endocrine system, like the nervous system, adjusts and correlates the activities of the various body systems. Endocrine integration is brought about by hormones. Hormones are chemical messengers produced by endocrine glands and endocrine cells in ans and tissues of the body. Some of the hormones are amines and others are amino acids, polypeptides, proteins and steroids. In general, the hormones regulate the processes of metabolism, growth and development, water and electrolyte balance, reproduction and behavior. The principal mechanisms by which hormones exert their intracellular effects are signal transduction pathways initiated by receptors. There are two important pathways by which most hormones function: (1) activation of second messenger systems (cAMP, IP3, DAG, and Ca2+) through membrane receptors acting via G-proteins or (2) regulation of gene transcription through intracellular receptors and transcription factors. Hormone secretion is usually controlled by negative and positive feedback mechanisms that ensure a proper level of hormone activity at the target tissue. This can display periodic variations. The major endocrine glands and their hormones are discussed in this chapter:
The pituitary and hypothalamus are an anatomical and functional unit. Six important hormones are secreted by the anterior pituitary, which plays major roles in the control of