Porth's Essentials of Pathophysiology, 4e

9 U N I T

Endocrine System

31

The Endocrine System Hormones

C h a p t e r

Structural Classification Hormone Synthesis Hormone Transport and Clearance from the Blood Receptor Control of Hormone Function Control of Receptor Number and Affinity Receptor Activation and Signaling Regulation of Hormone Levels Hypothalamic-Pituitary Regulation Feedback Regulation Diagnostic Tests

Mechanisms of Endocrine Control

Blood Tests Urine Tests Stimulation and Suppression Tests Genetic Tests Imaging Techniques

T

he endocrine system is involved in all of the integrative aspects of life, including growth, sex differentiation, metabolism, and adaptation to an ever- changing environment. This chapter focuses on general aspects of endocrine function, organization of the endo- crine system, hormone receptors and hormone actions, and regulation of hormone levels. The Endocrine System The endocrine system uses chemical messengers called hormones as a means of controlling the flow of infor- mation between the different tissues and organs of the body. It does not act alone, however, but interacts with the nervous system to coordinate and integrate the activ- ity of body cells. Each system can function alone or in concert with other systems as a single neuroendocrine system, performing the same general functions within the body of communication, integration, and control. Although both the endocrine and nervous systems function in regulating body functions, the means and speed of control used by these two systems are different. The nervous system functions by means of neurotrans- mitter molecules transported by neurons over a short distance to muscles and glands that respond within mil- liseconds (see Chapter 34). The endocrine system, on the other hand, uses hormones released from glands into the blood and transported throughout the body to influence the activity of body tissues. Tissue and organ responses to

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