THE ENDOCRINE SYSTEM

I. Overview of the Endocrine System

A. Regulates by working with the nervous system to maintain homeostasis.

B. Secretes substances called hormones that target specific cells.

C. Consists of ductless glands that secrete hormones into the bloodstream for regulation of the following:

• Development, temperature, sexual activity, digestion, growth, behavior, stress, metabolism and more.

Both the nervous system and the endocrine system cause responses by chemical messengers.

II. Seven Functions of Hormones

A. Regulate body chemistry. B. Regulate metabolism and energy balance.C. Regulate control of smooth and cardiac muscle and

gland secretion.D. Maintain homeostasis in cases of infection, trauma,

stress and starvation.E. Regulate some immune activities.F. Regulate growth and development.G. Regulate reproduction, production of egg and

sperm.

III. Classes of Hormones

A. Steroid Hormones -derived from cholesterol and released into the blood. Soluble in lipids which make up cell membranes. Enter cells and produce effect.

Ex. Testosterone, estrogen, aldosterone and cortisol.

Steroid hormones

B. Non-Steroid Hormones-include amines, peptides, proteins and glycoproteins. Bind to receptors and brings about change. (uses secondary messengers to make the change)

• Proteins- Ex. Growth hormone, prolactin• Peptides-Ex. Oxytocin, antidiuretic hormone• Glycoproteins-Ex. Thyroid stimulating hormone,

follicle stimulating hormone.• Amines Ex. Norepinepherine and epinepherine

Non-steroid hormones

IV. Control of Endocrine SystemControlled in three ways:

• The hypothalamus and anterior pituitary• The nervous system• Changes in the internal environment.

Hypothalamus • Regulates other glands to tell them when to

release their hormones

The Endocrine Glands