Endocrine System

1. Endocrine System Anatomy and Physiology April-13-2009 Jennifer Torres Susana Harris Anisha Fabien Adaobi Abaekobe

2. The Composition of the Endocrine System

3. Pancreas • Is a glandular organ that secretes digestive enzymes and hormones • Two hormones insulin and glucagon. Insulin and glucagon are secreted directly into the bloodstream, and together, they regulate the level of glucose in the blood. • Insulin lowers blood sugar and glucagon increases blood sugar. If insulin secreting cells do not work properly diabetes occurs. • The pancreas produces the body's most important enzymes. The enzymes are designed to digest foods and break down starches. • The pancreas also helps neutralize chyme and helps break down proteins, fats and starch.

4. Hypothalamus • The primary function of the hypothalamus is to maintain internal homeostasis . Factors such as blood pressure, body temperature, fluid and electrolyte balance, and body weight are held to a precise value called the set-point. • It synthesizes and secretes neurohormones, often called hypothalamic-releasing hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones. • The hypothalamus controls body temperature, hunger, thirst, fatigue, and circadian cycles. • The hypothalamus is responsive to: Light, Olfactory stimuli, Steroids, Neurally transmitted information from the heart, the stomach, and the reproductive tract, Autonomic inputs, Stress and Invading microorganisms

5. Thyroid • The thyroid is one of the largest endocrine glands in the body located in the neck inferior to the thyroid cartilage. • The function of the thyroid gland is to take iodine, found in many foods, and convert it into thyroid hormones: thyroxine (T4) and triiodothyronine (T3). • Thyroid cells are the only cells in the body which can absorb iodine. • An overactive thyroid releases too much T4 and T3 into the bloodstream, causing the metabolism to speed up too much. The most common cause is Graves’ disease. This is an autoimmune condition in which antibodies behave like TSH and stimulate the thyroid uncontrollably • An underactive thyroid releases too little T4 and T3 into the bloodstream, causing the metabolism to slow down too much. The most common cause is Hashimoto’s disease. This is an autoimmune condition in which white blood cells and antibodies attack the thyroid gland.

6. Adrenal • triangular glands located on top of both kidneys. • Each gland consists of a medulla which is surrounded by the cortex. • The medulla is responsible for producing epinephrine and norepinephrine (adrenaline). • The adrenal cortex produces other hormones necessary for fluid and electrolyte (salt) balance in the body such as cortisone and aldosterone. The adrenal cortex also makes sex hormones but this only becomes important if overproduction is present. • Each gland consists of a medulla which is surrounded by the cortex. • The medulla is responsible for producing epinephrine and norepinephrine (adrenaline). • The adrenal cortex produces other hormones necessary for fluid and electrolyte (salt) balance in the body such as cortisone and aldosterone. The adrenal cortex also makes sex hormones but this only becomes important if overproduction is present.

7. Pituitary • Also known as the hypophysis, is a roundish organ that lies immediately beneath the hypothalamus, resting in a depression of the base of the skull called the sellaturcica. Two parts: The anterior pituitary or adenohypophysis is a classical gland composed predominantly of cells that secrete protein hormones. The posterior pituitary or neurohypophysis is not really an organ, but an extension of the hypothalamus. It is composed largely of the axons of hypothalamic neurons which extend downward as a large bundle behind the anterior pituitary. The anterior pituitary synthesizes and secretes important endocrine hormones, such as ACTH, TSH, PRL, GH, endorphins, FSH, and LH. These hormones are released from the anterior pituitary under the influence of the hypothalamus. • The posterior pituitary stores and releases: Oxytocin and Antidiuretic hormone (ADH)

8. Insulin/Glucagon • Homeostasis is regulated by two hormones, insulin and glucagon which are both secreted by the endocrine pancreas.  The production of insulin and glucagon by these pancreatic cells ultimately determines if a patient has diabetes or another related problem • Insulin is secreted by the beta cells of the pancreas in response to high blood sugar, although a low level of insulin is always secreted by the pancreas. • Glucagon is secreted by the alpha cells of the pancreas when blood glucose is low.   Blood glucose is low between meals and during exercise.  When blood glucose is high, no glucagon is secreted from the alpha cells.  Glucagon has the greatest effect on the liver although it affects many different cells in the body.  Glucagon's function is to cause the liver to release stored glucose from its cells into the blood.

9. Videos • http://www.youtube.com/watch?v=7m5SDb_1ME8&feature=related • http://www.youtube.com/watch?v=eyO8Dim3T3U&NR=1 • http://www.youtube.com/watch?v=8k-UKR2vGsk

10. Sources Cited • www.google.com/endocrinesystem • http://biomed.brown.edu/Courses/BI108/BI108_2002_Groups/pancstems/stemcell/insulin_glucagon.htm • http://www.medbio.info/Horn/Time%203-4/homeostasis_2.htm • http://kidshealth.org/parent/general/body_basics/endocrine.html