L23 NPB 101 - Lecture 23 •  SmartSite: – ...

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Unformatted text preview: Lecture 23 •  SmartSite: –  Lecture 23 Notes •  Review –  Thyroid –  Adrenal •  Announcements: –  None •  Endocrinology –  Adrenal (Con<nued) –  Stress Response –  Endocrine Control of Metabolism –  Pancreas •  Reading (Recommended): –  Relevant por<ons Chapter 19 1 REV: •  Thyroid Gland –  Follicles secrete T3 and T4 –  Main determinant of basal metabolic rate –  Plays a crucial role in CNS development –  Cor<cal steroid hormones •  Adrenal •  Mineralocor<coids  ­ Mainly aldosterone •  Glucocor<coids  ­ Primarily cor<sol •  Sex hormones – Primarily DHEA –  Influence mineral balance, specifically Na+ and K+ balance –  Major role in glucose metabolism as well as in protein and lipid metabolism –  Medullary catecholamine hormones 2 REV: Cor<sol •  S<mulates hepa<c gluconeogenesis •  Inhibits glucose uptake and use by many <ssues, but not the brain •  S<mulates protein degrada<on in many <ssues, especially muscle •  Facilitates lipolysis •  Plays key role in adapta<on to stress •  At pharmacological levels, can have an< ­inflammatory and immunosuppressive effects •  Displays a characteris<c diurnal rhythm •  Secre<on –  Long ­term use can result in unwanted side effects –  Regulated by nega<ve ­feedback loop involving hypothalamic CRH and pituitary ACTH 3 Aldosterone •  Principal ac<on site is on distal and collec<ng tubules of the kidney •  Secre<on is increased by –  Ac<va<on of renin ­angiotensin ­aldosterone system by factors related to a reduc<on in Na+ and a fall in blood pressure –  Direct s<mula<on of adrenal cortex by rise in plasma K + concentra<on •  Regula<on of aldosterone secre<on is largely independent of anterior pituitary control 4 Adrenal Cortex Sex Steroids (DHEA) •  Secretes both male and female sex hormones in both sexes •  Dehydroepiandrosterone (DHEA) –  Only adrenal sex hormone that has any biological importance –  Overpowered by tes<cular testosterone in males –  Physiologically significant in females •  Growth of pubic and axillary hair •  Enhancement of pubertal growth spurt •  Development and maintenance of female sex drive 5 Steroidogenic Pathways for Major Steroid Hormones Fig. 19 ­8, pg. 699 6 Disorders of Adrenocor<cal Func<on •  Cor<sol hypersecre<on: Cushing’s syndrome –  Causes •  Adrenal tumors secre<ng cor<sol •  ACTH ­secre<ng tumor •  Hyperglycemia and glucosuria (adrenal diabetes) •  Abnormal fat distribu<ons •  Muscle, connec<ve <ssue loss –  Signs and symptoms •  Adrenocor<cal insufficiency: Addison’s disease –  Aldosterone deficiency –  Cor<sol deficiency •  Hyperkalemia (high K+) and hyponatremia (Low Na+) (most dangerous acutely) •  Poor response to stress •  Hypoglycemia •  Impaired sympathe<c/catecholamine induced vasoconstric<on 7 Adrenal Medulla •  Modified part of sympathe<c nervous system •  Primary s<mulus for increased adrenomedullary secre<on ac<va<on of sympathe<c nervous system by stress •  Releases epinephrine and norepinephrine –  Secreted into blood by exocytosis of chromaffin granules –  Vary in their affini<es for the different adrenergic receptor types •  Epinephrine –  Reinforces sympathe<c system in moun<ng general systemic “fight ­or ­flight” responses –  relaxes smooth muscle of blood vessels supplying skeletal muscles –  Maintenance of arterial blood pressure –  dila<on of airways in lungs –  induces liver to release glucose and fat cells to release fafy acids for fuel 8 Stress Response •  Pafern of reac<ons to a situa<on that threatens homeostasis •  Stress –  Generalized nonspecific response of body to any factor that overwhelms or threatens to overwhelm the body’s ability to maintain homeostasis –  Any noxious s<mulus that brings about the stress response •  Stressor Fig. 19 ­12, pg. 707 9 Stress Response •  All the ac<ons are coordinated by the hypothalamus •  Generalized stress response –  Ac<va<on of sympathe<c nervous system accompanied by epinephrine secre<on •  Prepares body for fight ­or ­flight response –  Ac<va<on of CRH ­ACTH ­cor<sol system •  Helps body cope by mobilizing metabolic resources –  Eleva<on of blood glucose and fafy acids •  Decreased insulin and increased glucagon secre<on –  Maintenance of blood volume and blood pressure •  Increased ac<vity of renin ­angiotensin ­aldosterone system and increased vasopressin secre<on 10 Major Hormonal Changes During the Stress Response Table 19 ­2, pg. 708 11 Integra<on of Stress Response Fig. 19 ­13, pg. 709 12 Endocrine Control of Fuel Metabolism 13 Metabolism •  Metabolism –  All the chemical reac<ons that occur within the cells of the body –  Includes reac<ons involving the degrada<on, synthesis, and transforma<on of proteins, carbohydrates, and fats •  Intermediary metabolism or fuel metabolism •  Nutrient molecules are broken down through the process of diges<on into smaller absorbable molecules –  Proteins → amino acids –  Carbohydrates → monosaccharides (mainly glucose) –  Dietary fats (triglycerides) → monoglycerides and free fafy acids 14 Anabolism & Catabolism •  Anabolism (Absorp<ve State) –  Fed State; Glucose is plen<ful and serves as major energy source –  Buildup or synthesis of larger organic macromolecules from small organic subunits –  Reac<ons usually require ATP energy –  Reac<ons result in •  Manufacture of materials needed by the cell •  Storage of excess ingested nutrients not immediately needed for energy produc<on or needed as cellular building blocks •  Catabolism (Postabsorp<ve State) –  Fas<ng state; Endogenous energy stores are mobilized to provide energy –  Breakdown or degrada<on of large, energy ­rich organic molecules within cells –  Two levels of breakdown •  Hydrolysis of large cellular molecules into smaller subunits •  Oxida<on of smaller subunits to yield energy for ATP produc<on 15 Summary of Reac<ons in Fuel Metabolism A P P A P A P A = Absorp<ve P = Postabsorp<ve Table 19 ­3, pg. 710 16 Interconversions Among Organic Molecules •  Most interconversion of organic molecules occurs in liver •  Essen<al nutrients (certain amino acids and vitamins) •  Food intake is intermifent – nutrients must be stored for use between meals –  Excess circula<ng glucose •  Stored in liver and muscle as glycogen •  Once liver and muscle stores are “filled up”, addi<onal glucose is transformed into fafy acids and glycerol and stored in adipose <ssue •  Become incorporated into triglycerides –  Excess circula<ng fafy acids –  Excess circula<ng amino acids •  Converted to glucose and fafy acids Fig. 19 ­14, pg. 711 17 Stored Metabolic Fuel in the Body Table 19 ­4, pg. 712 18 Roles of Key Tissues in Metabolic States •  Liver –  Primary role in maintaining normal blood glucose levels –  Principal site for metabolic interconversions such as gluconeogenesis –  Primary energy storage site –  Important in regula<ng fafy acid levels in the blood –  Primary site of amino acid storage –  Major energy user –  Normally can only use glucose as an energy source –  Does not store glycogen •  Mandatory blood glucose levels be maintained 19 •  Adipose <ssue •  Muscle •  Brain Endocrine Pancreas Glucagon Insulin 20 Pancreas Fig. 19 ­15a, pg. 715 21 Pancrea<c Hormones •  Pancreas –  Endocrine cells – Islets of Langerhans •  β (beta) cells –  Site of insulin synthesis and secre<on –  Produce glucagon –  Pancrea<c site of somatosta<n synthesis –  Least common islet cells –  Secrete pancrea<c polypep<de •  α (alpha) cells •  δ (delta) cells •  PP cells •  Insulin and glucagon –  Most important in regula<ng fuel metabolism 22 ...
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