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The Endocrine System a collection of glands that release hormones into the blood stream hormones are classified according to their activation site. Some affect many cells throughout the body (i.e. growth hormone, insulin, epinephrine (adrenaline)) and others target specific cells or tissues (i.e. parathyroid, gastrin). o what do they do?! (Hormones are chemical regulators produced by cells in one part of the body that affect cells in another part of the body.) Chemical Control Systems the endocrine system maintains control over a long duration (nervous system adjusts to short term more on this later) So… How does it work? the hypothalamus regulates the pituitary gland through nerve stimulation, but it is the pituitary gland that stimulates the glands of the endocrine system to release hormones How did scientists find out about the hormones that are in very low concentration in the blood? A lot of trial and error and “oops!” moments (often removing an organ and seeing what goes wrong) 1 Types of Hormones There are two types of hormones: steroid and protein Steroid hormones: made from cholesterol soluble in fat eg. sex hormones These hormones act by diffusing directly into the target cell and activating specific genes to illicit response. *see fig.4 pg. 374 for more detail. Protein hormones: made from amino acid chains water soluble eg. insulin and GH Chemical Signals How do hormones signal cells? Hormones can only affect the cells that contain the right type of receptor capable of recognizing and interacting with the hormone There are two types of hormones that differ in their structure as well as how they act upon target cells. (see page 374) 1. Steroid hormones enter the target cell by passing through the target cell membrane and binding to a receptor protein in the cytoplasm of the cell (see figure 4, p. 374) 2 the binding of the hormone to the regulatory sites (site other than active site) to induce or suppress the expression of specific genes in that cell 2. Peptide (protein) hormones Along with most hormones that are derived from amino acids, peptide hormones are not able to pass through the plasma membrane, thus they bind to specific receptors embedded on the outer side of the target cell’s plasma membrane. Creates a signal transduction pathway that converts the extracellular signal to intercellular signals that alter the target cells behaviour. (see figure 5, p. 375) In many cases the binding of the hormone to its receptor on the outside of the target cells activates a G protein which binds to an enzyme called adenylyl cyclase, activating it. Adenylyl cyclase catalyzes the conversion of ATP into cyclic AMP The production of cyclic AMP can be stopped by a second type of G protein which inhibits the activity of Adenylyl cyclase 3 Major Glands of the Endocrine System Pituitary Gland “master gland” (See section 8.1) pea sized gland located at the base of the brain that controls other endocrine glands and regulates body growth produces and stores hormones; hormones stored in the pituitary gland are secreted when stimulated by the hypothalamus via nerve impulses composed of two lobes: posterior and anterior posterior: stores many hormones produced by the hypothalamus (travel to pituitary gland through blood) anterior: produces its own hormones, BUT still under control of the hypothalamus (both +ve and –ve) …they act as a team! * See pg. 377 for summary of pituitary hormones Thyroid Gland an H-shaped gland in the front of the neck that secretes a hormone that controls the speed at which the body cells work (Section 8.3) 4 Secretion of thyroid hormones is under negative control (feedback) from the hypothalamus: via TSH. *See fig. 3 pg. 385 for diagram. See table 1, pg. 387 for a summary of thyroid hormones Parathyroid Glands 4 small glands located behind (in) the thyroid gland that regulate the Ca2+ (important in muscle function and much more) content in the blood (Section 8.3) See fig. 5 pg. 385 for diagram. See table 1, pg. 387 for a summary of parathyroid hormones Adrenal Glands located on kidneys – they regulate the use of carbohydrates and salts and prepare body for emergency by producing adrenaline (p. 381-382) Two glands; each gland is made of two glands encased in one shell: the adrenal cortex (outer), and the adrenal medulla (inner) Adrenal medulla: produces epinephrine (adrenaline) and norepinephrine (noradrenaline) Adrenal cortex: three different hormones: glucocorticoids, mineralocorticoids, sex hormones (androgens) in small amounts. See fig. 5 pg. 382 for diagram. See table 1, pg. 382 for a summary of adrenal hormones 5 Adjustment to Stress (section 8.4) Prostaglandins involved in stress response (among other things – there are 16 different types) by increasing blood flow, and relaxing smooth muscle in paths to lungs. * more localized response See table 1, pg. 388 for a summary See table 2, pg. 389 for Problems associated with long-term stress See table 3, pg. 391 for a list of banned performance enhancing drugs Pancreas a digestive gland that secretes pancreatic juice to small intestine and insulin into the blood stream. (See section 8.2) has two cell types: produces hormones AND enzymes in islets of Langerhans: produce insulin and glucagon β cells: produce insulin (when glucose ↑) : makes cells more permeable to glucose, therefore, blood glucose decreases * in liver, glucose is turned into glycogen (store) 6 α cells: produce glucagon (when glucose ↓): causes blood glucose to increase as glycogen is converted from the liver. See fig. 1 pg. 378 for diagram of feedback system involved. *Additional info on diabetes: see pg. 379. Sex Hormones: (Section 8.5) Ovaries female sex glands – estrogen and progesterone Estrogen and progesterone are involved in the complex female sexual cycle in which one egg matures aprox. every 28 days. Changes in these pituitary hormones cause changes in ovarian hormones: estrogen and progesterone throughout the cycle and through pregnancy if it occurs. Testes male sex glands – testosterone Testosterone stimulates spermatogenesis, devel. of male secondary sex characteristics, and is also associated w sex drive * see pg. 389-90 for more detail on anabolic steroids 7 Independent Reading Assignment Use your textbook, sections 8.1 through to 8.5 to help you complete the following chart below, for each of the following hormones: Pituitary Hormones Produced elsewhere Growth hormone (GH) Thyroid stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Follicle Stimulating hormone (FSH) Luteinizing hormone (LH) Prolactin Oxytocin Antidiuretic Hormone (ADH) Insulin Glucagon Epinepherine/Norepinephrine Cortisol Thyroxin Parathyroid Hormone Estrogen Pregesterone Testosterone The chart that you complete should have the following headings: Hormone Site of Target production tissues/organs Function Disease/ Ailments ….. You will be able to use your completed chart on you Unit Test, so it is important that you read your text carefully and provide a complete summary of these hormones. 8