Introduction to the Endocrine System

Learning Objectives

After studying this chapter, you will be able to:

  • Define and learn medical terminology associated with the endocrine system.
  • Identify the contributions of the endocrine system to homeostasis
  • Discuss the function and nature of hormones
  • Discuss the mechanisms of hormone action
  • Discuss the regulation of hormone levels through positive or negative feedback
  • Discuss endocrine gland stimuli
  • Summarize the site of production, regulation, and effects of the hormones of the pituitary, thyroid, parathyroid, adrenal, pineal and thymus glands
  • Discuss the hormonal regulation of the reproductive system
  • Explain the role of the pancreatic endocrine cells in the regulation of blood glucose
  • Discuss several common diseases associated with endocrine system dysfunction
This photo shows a young girl reaching for an orange leaf on an oak tree. She is on a walkway near a creek. The opposite shore is a deep slope covered with more trees in autumn colors.

A Child Catches a Falling Leaf.

The endocrine system works with the nervous system to coordinate and direct the activity of the body’s cells.  It provides a slower, but longer lasting coordination than the nervous system.

The endocrine system uses chemical messages in the form of hormones- chemical substances that are secreted by cells into extracellular fluids and regulate metabolic activity.  Blood  transfers hormones to target sites.  Target cells or target organs -certain tissues or organs that a hormone affects.  Target cells must have specific protein receptor in order to be affected by the hormone.

You may never have thought of it this way, but when you send a text message to two friends to meet you at the dining hall at six, you’re sending digital signals that (you hope) will affect their behavior—even though they are some distance away. Similarly, certain cells send chemical signals to other cells in the body that influence their behavior. This long-distance intercellular communication, coordination, and control is critical for homeostasis, and it is the fundamental function of the endocrine system.

Hormones of the endocrine system coordinate and control growth, metabolism, temperature regulation, the stress response, reproduction, and many other functions.