Transcript Chapter 14
Chapter 14 Endocrine System Human Anatomy Sixth Edition Kent M. Van De Graaff (c) The McGraw-Hill Companies, Inc. The Endocrine System Chapter Concepts 1. Glands can be classified structurally and functionally as endocrine or exocrine. 2. Both the nervous and endocrine systems work together through different modes of action to regulate body activities and maintain homeostasis. 3. Hormones are transported by the blood to target cells where they are responsible for specific functions. 4. Elaborate feedback mechanisms ensure homeostasis within the body systems. 5. Alterations in hormonal balance may result in serious clinical manifestations. It’s All About the Anatomy And maybe a little chemistry …… Groups of three or four Books closed and whatdaya know? The Endocrine System Objectives for Today 1. Distinguish between endocrine and exocrine glands 2. Compare and contrast the nervous and endocrine systems with regard to body regulation and homeostasis 3. Define mixed gland and identify them 4. Describe the action of a hormone on its target 5. Differentiate between the three principle kinds of hormones Endocrine versus Exocrine Glands In groups, compare the diagrams on the next slide using the similarities and differences routine. How can endocrine glands be distinguished from exocrine glands? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Endocrine versus Exocrine Glands Exocrine Produce secretions transported through ducts to destination Endocrine • Ductless • Secrete specific chemicals (hormones) into circulation • Target cells Endocrine versus Nervous System Endocrine System Secretes hormones Travel through bloodstream Action relatively slow Effects are prolonged Nervous System Electrochemical impulses via neurons Rapid response Effects are brief Two systems are closely coordinated in autonomically controlling the functions of the body. Glands of the Endocrine System Distributed throughout the body Introductory Video Endocrine Organs Cranial Cavity Neck Abdomen Mixed Glands Have exocrine as well as endocrine functions Glands of the Endocrine System QUIZ TIME! Glands of the Endocrine System Distributed throughout the body Cranial cavity: pituitary gland, hypothalamus, pineal gland Neck: thyroid and parathyroid glands Abdomen: adrenal glands and pancreas Pelvic cavity: gonads of the female Scrotum: gonads of the male Other Endocrine Tissues Several of the "other" endocrine cells and tissues are sometimes referred to as the diffuse endocrine system Many organs house clusters of cells that secrete hormones. The kidney, for example, contains scattered cells that secrete erythropoietin, a hormone essential for production of red blood cells. Even the heart contains cells that produce atrial naturetic hormone, which is important in sodium and water balance. Hormones Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Act as chemical messengers Three basic kinds: Proteins Steroids Amines Derived from amino acids or cholesterol Steroid Hormones Soluble in lipids Pass through cell membrane Steroid-protein complex stimulates gene expression Steroid hormone response Hormones (Intracellular Receptors) Despite the molecular diversity of hormones, all hormone receptors can be categorized into one of two types, based on their location within the cell: Location of Receptor: Intracellular receptors – cytoplasm and/or nucleus Classes of Hormones: Steroids and Thyroid Hormones Principle Mechanism of Action: Alter transcriptional activity of responsive genes Protein and Amine Hormones Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Insoluble in lipids Requires receptors on cell membrane Receptor binding increases adenylate cyclase activity ATP converted to cyclic AMP Stimulates change in cellular processes Hormones (Cell surface receptors) Despite the molecular diversity of hormones, all hormone receptors can be categorized into one of two types, based on their location within the cell: Location of Receptor: Cell surface receptors (plasma membrane) Classes of Hormones: Proteins and Amines Principle Mechanism of Action: Generation of second messengers which alter the activity of other molecules usually enzymes - within the cell Control of Hormone Secretion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Negative Feedback Maintains status quo Gland continues to secrete until target cells provide message to stop Message is generally in form of a second hormone Signals endocrine organ to stop Control of Hormone Secretion (2) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Neural Impulses Autonomic nervous system Causes endocrine gland to secrete (e.g. adrenal gland) Mind/body connection Hypothalamus secretes releasing factors Stimulates cells of pituitary to secrete hormones The Pituitary Gland Objectives 7. Describe the actions of anterior pituitary hormones 8. Explain how secretions from the anterior and posterior pituitary are controlled by the hypothalamus 9. Explain how the secretion of anterior pituitary hormones is regulated by negative feedback Pituitary Gland - Anatomy Region of the diencephalon Attached to brain by pituitary stalk Contains infundibulum Adenohypophysis (Anterior lobe) Secrete hormones Neural control by hypothalamus Negative feedback control Neurohypophysis (Posterior lobe) Releases hormones produced by hypothalamus The Pituitary Gland Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pituitary Gland Structure Copyright Copyright © © The The McGraw-Hill McGraw-Hill Companies, Companies, Inc. Inc. Permission Permissionrequired required for for reproduction reproduction or or display. display. Adenohypophysis Pars distalis (anterior pituitary) Pars tuberalis Neurohypophysis Lobus nervosa Infundibulum Connects to hypothalamus Posterior Pituitary Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stores and releases hormones produced by hypothalamus Specialized neurons Hormones transported along axons in the hypothalamo-hypophyseal tract (within infundibulum) Anterior Pituitary – Hormones (1) Growth Hormone (GH) Stimulates cell growth Stimulates mitosis Regulated by the hypothalamus Thyroid Stimulating Hormone (TSH) Regulates thyroid gland Adrenocorticotropic hormone (ACTH) Promotes normal function of adrenal cortex Breakdown fats Anterior Pituitary – Hormones (2) Luteinizing hormone (LH) Onsets ovulation Stimulates corpus luteum Stimulates release of progesterone Follicle Stimulating Hormone (FSH) Regulates development of follicle Stimulates release of estrogen GONADOTROPHINS Anterior Pituitary – Hormones (3) Prolactin Assists with milk production Melanocyte Stimulating Hormone (MSH) Darkens skin Endocrine functions unclear Anterior Pituitary - Summary Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior Pituitary – Hormones Oxytocin Influences activity of female reproductive system Released at end of gestation Causes uterine contractions Milk ejection reflex during lactation Antidiuretic Hormone (ADH) Inhibits formation of urine Reduces water excretion Hypothalamo-hypophyseal Portal System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hypothalamus Hormones Median Eminence Primary Capillaries Pituitary Stalk Secondary Capillaries Pars Distalis Thyroid and Parathyroid Gland Objectives 10. Describe the location and structure of the thyroid gland and list the actions of thyroid hormones 11. Describe the location and structure of the parathyroid gland and list the actions of parathyroid hormone Regulated by hypothalamus Regulated by TSH Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. In the neck Below larynx Two lobes Separated by isthmus Thyroid Gland Function Thyroxin (T4) Triiodothyronin (T3) Release is controlled by hypothalamus (TSH) Regulate metabolic rate Increase protein synthesis Iodine essential for hormone production Calcitonin Regulates calcium levels in blood Decreases breakdown of bone Stimulates excretion of Ca++ at kidney Decreases blood Ca++ levels Goiter Formation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lack of iodine Interferes with negative feedback control of TSH Results in abnormal enlargement of the thyroid gland Parathyroid Gland Embedded in posterior surface of thyroid gland Usually four glands (superior and inferior pair) Parathyroid hormone (PTH) Increases blood Ca++ levels Acts on bone, kidney, small intestine Actions of Parathyroid Hormone Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Opposes effects of calcitonin Increase in PTH causes Bones to release calcium Kidneys to conserve calcium Small intestine to absorb calcium Negative feedback control Pancreas Objectives 12. Describe the structure of the endocrine portion of the pancreas and the origin of insulin and glucagon 13. Describe the actions of insulin and glucagon Pancreas Mixed gland Endocrine portion: Pancreatic Islets 2 cell types: Alpha – glucagon Beta – insulin Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Endocrine Function of the Pancreas Glucagon Stimulates liver Glycogen to glucose Increase blood glucose Insulin Decrease blood glucose Promotes muscle/adipose cells to take up glucose Stimulates glucose to glycogen in muscle/liver Failure of beta cells = diabetes mellitus Adrenal Gland Objectives 14. Describe the location of the adrenal glands and distinguish between the adrenal cortex and the adrenal medulla 15. List the hormones secreted by the adrenal glands and discuss their effects Adrenal Gland Paired organ Superior border of kidney Adrenal Medulla Chromaffin cells Sympathetic innervation Catecholamines Adrenal Cortex Bulk of gland Corticosteroids Adrenal Gland Function Adrenal Cortex Mineralocorticoids Regulate electrolytes Aldosterone Increase water retention Decrease urine output Glucocorticoids Carbohydrate, protein, fat metabolism Anti-inflammatory Regulated by ACTH Gonadocorticoids Supplement sex hormones Adrenal Medulla Epinephrine and norepinephrine Effects similar to ANS except hormonal effects are 10 times longer lasting Prepares body for greater activity Stress Physiological change in the body Elicited by neural impulses from hypothalamus Adrenal medulla releases epinephrine Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Other Endocrine Glands Objectives 16. Discuss the endocrine functions of the gonads 17. Describe the structure and location of the pineal and thymus glands and their endocrine functions Gonads Testes Ovaries Mixed gland Produce estrogen Development of secondary Interstitial cells sex organs produce testosterone Menstrual changes Development of Promotes secondary sex secondary sex organs characteristics Promotes secondary Produce progesterone sex characteristics Associated with pregnancy Prepare uterus for implantation Pineal Gland Small cone-shaped organ Roof of third ventricle Innervated by the sympathetic NS Secretes melatonin Rhythmic daily release (circadian) Thought to affect hypothalamus Thymus Upper mediastinum Front of aorta Associated with lymphatic system Thymosin Stimulates T-cell production Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The End.