Test 2 - The Endocrine System The endocrine system exerts...

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The Endocrine System The endocrine system exerts slow, sustained control over organ functions. 1. The endocrine system secretes hormones. a. What is a hormone? -hormones control long term functions -hormones are chemical messengers secreted into bloodstream by endocrine glands b. Endocrine glands are Widespread -allow you to maintain BP over 25 years c. Continuum 2. Transport of Hormones a. Usually attached to a carrier 1. Albumin -same protein as egg white 2. (Hormone name) binding globulin -a globe shaped protein A. Thyroxine-binding globulin (TBG) 3. Prevents loss of the hormone in urine -saves ½ life of hormones in min/sec 4. Free v Bound Hormone (not active) -free is active ~ 10% -binding acts as a buffer 3. Classification of Hormones a. Amino acid derivatives -very small molecules, nt -derived from single a.a. -E and NE, a.a.’s, melatonin b. Peptides and proteins -all hormones released by pituitary in this group c. Steroids -cholesterol based -glucocarticoids -mineralic d. Eicosanoids -fatty acids, arachidonic acid-based -local mediators not in bloodstream as much -prostaglandin-pain response 4. Depending on the chemical makeup of the hormone, it will have a very specific way in which it is carried in the blood and not on the target cell. Protein Hormones Steroid and Thyroid Hormones •Hydrophilic -therefore they can travel freely in blood •Hydrophobic -therefore they require a protein carrier to help them circulate in blood
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•Hydrophilic -therefore they cannot diffuse through cell membrane •Hydrophobic -therefore they can diffuse easily through the cell membrane •Receptor -must be located on cell membrane of the target cell since it cannot diffuse into the cell •Receptor -located inside target cell -notice that whether the hormone is hydrophilic or hydrophobic determines how it is carried and acts on the target cell 5. Mechanisms of Action a. Fat-soluble hormones such as steroids, bind to intranuclear receptors. -a hormone carrier complex translocates to the nucleus, where it binds to a receptor and triggers transcription -hormone response elements (HRE) b. Non-fat soluble hormones use 2 nd messenger system 1. Second Messenger cAMP 1. Binding of hormone (1 st messenger) to its receptors activate G proteins, which activate adenylate cyclase 2. Activated adenylate cyclase converts ATP to cAMP 3. cAMP serves as a 2 nd messenger and activates protein kinases 4. Activated protein kinases phosphorlyate other enzymes 5. Millions of phosphorylated enzymes catalyze reactions that produce physiological responses -book: 1. Hormone receptor binding activates a G protein 2. G protein activates adenylate cyclase 3. Adenylate cyclase produces cAMP 4. cAMP activates protein kinases 5. Protein kinases phosphorylate enzymes. This activates some enzymes and inactivates others 6. Activated enzymes catalyze metabolic reactions with a wide range of possible effects on the cell -know these 8 hormones that are active due to 2 nd messenger systems 1. ACTH 2. FSH 3. LH 4. PTH 5. TSH 6. Glucagon 7. Calcitonin 8. Catecholamines (E and NE)
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2. Second Messenger System Calcium
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This note was uploaded on 03/20/2008 for the course CBIO 2210 taught by Professor Wenzel during the Spring '07 term at University of Georgia Athens.

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Test 2 - The Endocrine System The endocrine system exerts...

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