The human endocrine system is a complex biological messaging system. Just like the nervous system transmits messages throughout the body by releasing and receiving neurotransmitters along a pathway of nerves, the endocrine system releases chemical messengers called hormones which control many bodily functions. While the nervous system is often thought of as controlling muscular activity (heartbeat, breathing, eye blinks, etc…) the endocrine system is considered the prime mechanism for controlling metabolism, growth and moods.
Hormones themselves are generally broken down into three broad classes. The main class is the steroid. This group is further broken down into five subclasses, based on the receptors for the steroid. Those classes are androgens, estrogens, glucocorticoids, mineralocorticoids, and progestagens. The second broad class of hormones is the peptide hormone and protein hormone group. The third broad class of hormones is the amine hormone group. This group is so named because the hormones are based on amino acid structures.
Endocrinology is a very complex subject. The major glands of the endocrine system are the hypothalamus, the pituitary gland, the adrenal glands, the thyroid and the pancreas. However, many other organs also secrete chemical messengers and are considered part of the endocrine system. The kidneys, liver and even fat tissues secrete endocrine chemicals.
There are five general types of chemical messengers which, as a whole, comprise the endocrine system. Hormones are the chemical messengers produced by ductless, vascular glands. These messengers transmit what are called endocrine signals. Metabolic signals are transmitted by chemicals secreted from exocrine glands. These would be secretions like saliva, gastrointestinal acids and perspiration from sweat glands. Autocrine, paracrine and juxtacrine signals are transmitted from glands or cells in the body and effect organs or cells nearby. Some are produced by cell membranes and act upon those particular cells. They do not have to travel throughout the body as does, for example, insulin or estrogen.
by : Claudia Clamicca