L23_NPB_101 - Lecture 23 •  SmartSite: – ...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

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 & Adrenal •  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 •  Epinephrine (80%) and Norepinephrine (20%) 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: e.g., 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: e.g., Addison’s disease –  Aldosterone deficiency •  Hyperkalemia (high K+) leads to heart arrhythmias •  Hyponatremia (Low Na+) low blood volume & blood pressure (most dangerous acutely) •  Poor response to stress •  Hypoglycemia •  Impaired sympathe<c/catecholamine induced vasoconstric<on 7 –  Cor<sol deficiency 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 faiy acids for fuel 8 General Adapta<on Syndrome (GAS) •  Paiern 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 faiy 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 faiy 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 intermiient – 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 faiy acids and glycerol and stored in adipose <ssue •  Become incorporated into triglycerides –  Excess circula<ng faiy acids –  Excess circula<ng amino acids •  Converted to glucose and faiy 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 faiy 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 ...
View Full Document

This note was uploaded on 11/15/2010 for the course BIO NPB 101 taught by Professor Dr.weidner during the Fall '10 term at UC Davis.

Ask a homework question - tutors are online