3. Hormones - Chemicals secreted in one area of the body that affect responses in other areas. chemical messengers

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1 Endocrine System A. The human endocrine system consists of: 1. Pituitary Gland - AKA Master gland. Located in the brain and controls the activity of many endocrine glands 2. Hypothalamus - connects the pituitary gland to the brain. Controls the release of hormones from the pituitary. (Major link between the CNS and the endocrine system) 3. Hormones - Chemicals secreted in one area of the body that affect responses in other areas. chemical messengers Comparison of the endocrine and nervous system: 1. The endocrine system works together with the central nervous system to maintain homeostasis 2. CNS sends messages via nerves. Endocrine system sends hormones via blood stream. 3. The endocrine system uses both positive and negative feedback loops B. Glands 1. Are organs made of epithelial cells that specialize in the secretion of substances needed by the organism. 2. There are two different types of glands in the human body. a. Exocrine : 1. The glands that discharge their secretion into ducts 2. Ducts then carry secretions to where they are used: eg. Digestive glands b. Endocrine --- glands that secrete directly into the blood stream. AKA ductless glands C. Target Cells, Target Tissues : 1. Each hormone is recognized only by specific cells and/or tissues. Hormones may stimulate the target cells and increase activities or inhibit and decrease activity. Done by changing the rates of biochemical reactions.

2 D. Regulation of Hormone Secretion 1. Our body does not secrete hormones at a constant rate. The rate varies with the needs of the body. 2. Negative Feedback - A type of self regulation. It operates on the principle that the level of one hormone in the blood inhibits the production of another hormone. Very much like a thermostat it has a set point that it always goes back to turns on when a hormone is too low and off when a hormone is too high. 3. Positive Feedback Also a type of regulation. There is no set point however. It is designed to intensify the input. Ex: During childbirth a hormone called oxytocin is released which causes contractions of the uterus. The contractions cause more oxytocin to be released which causes more contractions etc.. It keeps building and building until the baby is expelled. 3. Tropic Hormones - The chemical substance that affects the secretion of other glands II. The Endocrine Glands A. Hypothalamus: 1. Located in the brain 2. Receives information from the CNS and passes information to the pituitary gland. The major link between CNS and endocrine system 3. Directs the work of the pituitary gland. B. Pituitary Gland 1. A small gland below the hypothalamus - base of brain 2. Functions : a. secretes hormones b. controls the activity of other endocrine glands c. consists of and anterior (front) and posterior (back) lobe d. stimulating hormones

3 3. Secretions of the pituitary a. THS (thyroid stimulating hormone) - stimulates the thyroid gland to produce its hormone (thyroxine). Contains iodine - Regulates metabolism in body. Needed for normal physical and mental development. b. ACTH (Adrenocorticotropic Hormone) - releases hormones from the adrenal gland. Stimulates the adrenal gland to secrete hormones. c. GH (growth hormone) - Controls the rate of growth. In childhood works on bones. d. FSH (follicle stimulating hormone) - stimulates the development of cells in the ovaries of females and production of sperm in males e. LH (luteinizing hormone) - stimulates production of sex hormones in males and females. Also in females causes the release of eggs from the ovaries f. ADH (Anti-diuretic hormone) - controls re-absorption of water in kidneys. Alcohol inhibits the secretion. Therefore urination increases. C. Thyroid 1. Located in the neck below the larynx and in front of the trachea 2. Secretes thyroxine. An iodine containing hormone 3. Calcitonin - controls calcium metabolism 4. Essential for normal mental and physical development. Influences the rate of metabolism in the body. D. Parathyroid Glands 1. Located in the back of the thyroid - 4 small oval shaped glands 2. Secretes parathyroid hormone a. regulates calcium and phosphate metabolism b. calcium teeth, blood clotting, and nerve function c. Phosphate needed for ATP, DNA, and RNA E. Adrenal Glands (2)- help the body deal with stress 1. Located on the top of each kidney 2. Each gland has two parts a. Medulla - inner part releases hormones that handle stress (epinephrine AKA adrenalin and norepinephrine) b. Cortex outer layer helps the body deal with long term stress. Secretes corticosteroids.

4 F. Pancreas - Islets of Langerhans 1. Located below the liver above the large intestine 2. Function - exocrine function produces digestive juices into the pancreatic duct. Endocrine secretions control carbohydrate metabolism a. Insulin - glucose metabolism. Controlled by concentration of glucose in blood. Helps change glucose into glycogen. Also turns excess glucose into fat (when blood sugar level increases). b. Glucagon - Opposite effects of insulin - breaks down glycogen into glucose. breaks fat into glucose (when blood sugar is low) G. Gonads 1. Located in the ovaries of females and in testes of males 2. Testes in Males a. secrete sex hormones called androgens. Most important testosterone. Responsible for the development of male reproductive system. Secondary sex development - beard growth and deep voice 3. Ovaries in Females a. Produce estrogen and progesterone. Estrogen influences the development of secondary sex development. Progesterone deals with menstruation H. Thymus Gland 1. Located in upper chest near the heart 2. Secretes thymosin - stimulates the development of T Lymphocytes I. Pineal Gland 1. Located at the base of the brain (it is pea sized) 2. Secretes meltonin - may inhibit sexual development in males and Females

5 Malfunctions of the endocrine System Hypersecretion - An excess of a hormone - too much has been secreted Ex: giganticism too much growth hormone Hyposecretion - A deficiency of a hormone - not enough has been secreted Ex: dwarfism too little growth hormone Goiter - Enlargement of thyroid gland. Due to iodine deficiency (use salt in diet to prevent). Inhibits the production of thyroxine. Diabetes Type I: aka juvenile diabetes no insulin is being secreted Type II: aka adult diabetes not enough insulin is being produced or The body isn t using the insulin properly * Both types are genetically linked w/ type II being more prevalent In 1920 Frederick Banting discovered what causes diabetes and in 1922 began the first experiments using injections of insulin