Endocrine+system

The **endocrine system** is a collection of physically disconnected organs, each of which produces and secretes chemicals called hormones into bloodstream in order to maintain homeostasis, which includes: growth and development control and responses to changing environment (Nowicki 874). There are 7 major glands of the endocrine system located at different parts of the human body. They are hypothalamus, pituitary gland, pineal gland, thyroid and parathyroid glands, thymus, pancreas, adrenal glands, and gonads (ovaries in women and testes in men). **Endocrine glands** are found in many different parts of the body. It is the organs where hormones are made (Nowicki 899), The **pituitary gland** is in the middle of the brain that makes and releases hormones that control cell growth and concentration of water in the blood. It also stimulates the adrenals, thyroid, and gonads (Nowicki 898). This visual below is of where the glands are and the hormones each secretes.

This image below explains what body process each gland regulates: For more detailed information about location of endocrine glands and how it affects human body, can you click this link: http://www.ivy-rose.co.uk/HumanBody/Endocrine/Endocrine_Glands.php

The chemical signals made by the endocrine system are called **hormones** (Nowicki 896). All hormones belong to one of two categories: steroid hormones and non-steroid hormones. All steroid hormones are made of cholesterol, a type of lipid. On the other hand, there are three types of non-steroid hormones that are made up of one or more amino acids (Nowicki 896). Illustration below compares how are the two steroid and non-steroid hormones differ in its action. A steroid hormone can enter its target cells by diffusing through the cell membrane. Once inside, the steroid hormone attaches to a receptor protein, which transports the protein into the nucleus. After it is inside, the steroid hormone binds to the cell's DNA. This binding causes the cell to produce the proteins that are coded by that portion of DNA (Nowicki 897). Non-steroid hormones don't enter their target cells. These hormones bind to protein receptors on a cell's membrane and cause chemical reactions to take place inside the cell. This chemically-changed receptor activates molecules inside the cell. These molecules, called the secondary messengers, react with still other molecules inside the cell. The products of these reactions might initiate other chemical reactions in the cell or activate a gene in the nucleus (Nowicki 897).
 * //How the Endocrine System functions://**

//**Hormone-targeted cell binding:**// Different hormones are produced in different glands of the endocrine system. All hormones get into the bloodstream. As a hormone move through the body, it comes into contact with many different cells. But it will interact only with a cell that has specific membrane receptors. If the hormone touches a cell that does not have a matching receptor, nothing happens. If it touches a cell that has the correct receptors, it binds to the cell and prompts the cell to make certain protein or enzymes. Cells that have receptors for a hormone are called the target cells of that hormones (Nowicki 896). Illustration below summarizes the idea.

//**Hypothalamus is involved in the nervous and endocrine system:**// //**Homeostasis maintenance through negative feedback loop:**// The hypothalamus receives nerve impulse about the excess stress level. Then it secrets the CRH hormone that later ignites the pituitary gland to produce ACTH hormone. ACTH travels through the blood stream to the adrenal glands, which produces cortisol to lower the stress level in the body. As the body becomes more relaxed, less and less neuron impulse about stress comes to the hypothalamus, thus less hormone at each station is produced, and the cycle is turned off. //**Hormonal imbalances can cause severe illness:**// Basically, there are 3 types of hormonal disorders:
 * Hypothalamus** is a small area of the middle of the brain that stimulates the pituitary gland and controls growth, reproduction, body temperature, etc (Nowicki 898). Hypothalamus's role in the nervous system is it receives, sorts, and interprets information from sensory organs. Then, as part of the endocrine system, the hypothalamus produces releasing hormones that affect tissues and other endocrine glands. **Releasing hormones** stimulate other glands to release their hormones (Nowicki 900). In fact, many of the hypothalamus's releasing hormones affect the pituitary gland. Thanks to a series of short blood vessels connects the two, these glands can quickly pass hormones back and forth (Nowicki 900). Together, the hypothalamus and pituitary gland help maintain many aspect of homeostasis such as, body temperature, blood water levels, hunger, maintenance of salt and ion levels in the blood, regulation of blood pH**//.//**
 * 1) Overproduction of a hormone
 * 2) Underproduction of a hormone
 * 3) Receptors don't function properly cause target cells to become insensitive to hormone

Hormones are very strong chemical. Little amount can make substantial impact on chemistry of human body. If a hormone is overproduced, cortisol for example, the body cannot metabolize sugars properly, and a person can develop Cushing's Syndrome. If a hormone is too-little-produced, thyroid hormones for instance, causes weakness, sensitivity, to cold, weight gain, and depression. In the third scenario, there are a wide spectrum of what a person may get if his/her receptors don't work (Nowicki 901). For more information, please click: http://www.hormone.org/Public/conditions.cfm

Explore the Endocrine System through animations: http://classes.midlandstech.com/carterp/courses/bio211/endocrine.htm Explore the Endocrine System with texts: http://knight.noble-hs.sad60.k12.me.us/content/exploringLife/text/chapter32/concept32.4.html http://biology.clc.uc.edu/courses/bio105/endocrin.htm http://www.emedicinehealth.com/anatomy_of_the_endocrine_system/article_em.htm#Endocrine%20System%20Introduction http://www.ivy-rose.co.uk/HumanBody/Endocrine/Endocrine_Glands.php http://www2.estrellamountain.edu/faculty/farabee/biobk/biobookendocr.html