Communication between organs and organ

 system is vital. It allows the body to adjust the function of each organ according to the needs of the whole body. Through communication, the body keeps itself in balance -a

concept called homeostasis. Communication to maintain homeostasis can take place through the nervous system or through chemical

stimulation. Chemicals that communicate are called transmitters. Transmitters that are

produced by one organ and travel to other organs through the blood stream are called hormones.

Hormones are released into the bloodstream from a gland or organ that affect activity in cells at another site. Most hormones are protein

composed of amino acid chains of varying length. Others are steroids, fatty substances derived from cholesterol. Very small amounts of hormones can trigger very large responses in the body.  They control growth and development, reproduction and sexual characteristics. They influence the way the body uses and stores energy.

Cover story for this week is on Hormones. Some

hormones affect only one of the organs, while others affect the whole body.  Thyroid stimulating hormone is produced in the pituitary gland and affects only the thyroid gland. Thyroid

hormone is produced in the thyroid gland, but it affects cells throughout the body. Insulin

produced by the islet cells of the pancreas, affects the metabolism of glucose, protein and fat throughout the body.