Endocrine System 2014 Anatomy K and L Mrs. Shott Homeostasis is preserved through intercellular communication • Nervous system and Endocrine system work together to maintain homeostasis • HOW DO THEY COMMUNICATE? • Chemical messengers called HORMONES – relay info between cells • Hormones act on target cells or tissues that respond to the presence of the hormone 10-1 – Comparison of Nervous and Endocrine • Nervous System – FAST • Endocrine – Slow, and ongoing action -Both systems rely on chemicals that bind to specific receptors on target cells - Both systems SHARE various chemical messengers -Both systems regulated mainly by negative feedback -Both systems coordinate and regulate activities of other cells and tissues, organs and systems to maintain homeostasis Endocrine vs Exocrine • Endocrine cells – glandular secretory cells that release their secretions into the extracelluar fluid • Exocrine cells – release their secretions into epithelial surfaces 3 Classes of Hormones 1. Amino Acid derivatives – structurally similar to amino acids (the building blocks of proteins) • Examples: • Epinephrine, Norepinephrine, Thyroid hormones and Melatonin 3 Classes of Hormones 2. Peptide hormones – chains of amino acids Examples: Antidiuretic hormone (ADH), Oxytocin, Growth hormone (GH), Prolactin (PRL) 3 Classes of Hormones 3. Lipid Derivatives – there are 2 classes of lipid based hormones: steroid hormones and eiocosanoids Steroid hormones – lipids that are structurally similar to cholesterol; released by the reproductive organs and adrenal glands; not water soluble, bound to specific transport proteins in blood Eiocosanoids – fatty acid based compounds derived from arachidonic acid; includes prostaglandins Peptides Insulin Glucagon Growth hormone Vasopressin (ADH, Antidiuretic hormone) Prolactin Erythropoietin Atrial natriuretic peptide (ANP) Amines T4 (thyroxine) Norepinephrine T3 (triiodothyronine) Epinephrine Melatonin Steroids Estradiol Aldosterone Cortisol Testosterone Glucocorticoids – cortisol, corticosterone, cortisone Calcitriol Progesterone Estrogens Control of Endocrine Activity • Hormonal secretion is controlled by negative feedback mechanisms • Levels of hormone secretion can be affected by: • Levels of certain substances in the blood • Hormonal stimuli – changing levels in circulating hormones • Neural stimuli – resulting from the arrival of neurotransmitter at a neuroglandular junction Hypothalamus – provides highest level of endocrine control It links the nervous and endocrine systems Hypothalamus Pituitary glandTarget cell or tissue 1. It acts as an endocrine organ by releasing hormones into the bloodstream at the posterior lobe of the pituitary gland 2. It secretes regulatory hormones that control the activities of endocrine cells in the anterior lobe of the pituitary gland 3. It exerts direct neural control over the endocrine cells of the adrenal medulla Pituitary Gland • Divided into 2 portions – • Anterior lobe – produces 7 hormones and is composed of glandular tissue • Posterior lobe – produces 2 hormones and is composed of neural tissue (axons of hypothalamic neurons that manufacture hormones) Figure 10-6 The Hypophyseal Portal System and the Blood Supply to the Pituitary Gland. Hypothalamic nuclei producing ADH and oxytocin Hypothalamic neurons producing regulatory hormones HYPOTHALAMUS Optic chiasm Capillary beds ANTERIOR LOBE OF PITUITARY GLAND Mamillary body Hypophyseal artery Infundibulum Portal veins Hypophyseal artery POSTERIOR LOBE OF PITUITARY GLAND Endocrine cells Hypophyseal veins © 2013 Pearson Education, Inc. Anterior Lobe of Pituitary Gland 1. TSH – Thyroid stimulating hormone = triggers the release of thyroid hormones 2. ACTH – Adrenocorticotropic hormone = stimulates the release of glucocorticoids by the adrenal glands 3. FSH – Follicle stimulating hormone = stimulated estrogen secretion and egg development in females and sperm production in males 4. LH – Luteinizing hormone = causes ovulation and progestin production in females and androgen (testosterone) production in males Anterior Lobe of Pituitary Gland 5. PRL – Prolactin = stimulates the development of the mammary glands and the production of milk 6. GH – Growth hormone = stimulates cell growth and replication by triggering the release of somatomedins (a family of growthpromoting proteins produced by the liver, skeletal muscle, bone and other tissues) from liver cells 7. MSH – Melanocyte stimulating hormone – may be secreted during fetal development, early childhood, pregnancy, or certain diseases. Stimulates melanocytes to produce melanin Posterior Lobe of Pituitary Gland 1. ADH – Antidiuretic hormone = decreases the amount of water lost at the kidneys (secreted primarily by the supraoptic neurons) 2. OXT – Oxytocin = in females oxytocin stimulates smooth muscle cells in the uterus and contractile cells in the mammary glands. In males it stimulates the contractions of the smooth muscles in the sperm duct and prostate gland. (secreted primarily by the paraventricular neurons) Figure 16.5 The hypothalamus controls release of hormones from the pituitary gland in two different ways. (1 of 2) Posterior Pituitary: Paraventricular nucleus Hypothalamus Posterior lobe of pituitary Optic chiasma Infundibulum (connecting stalk) Hypothalamichypophyseal tract Supraoptic nucleus Inferior hypophyseal artery Axon terminals 2 Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary. 3 Oxytocin and ADH are stored in axon terminals in the posterior pituitary. Posterior lobe of pituitary Oxytocin ADH © 2013 Pearson Education, Inc. 1 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). 4 When hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood. Figure 16.5 The hypothalamus controls release of hormones from the pituitary gland in two different ways. (2 of 2) Anterior Pituitary: Hypothalamus Anterior lobe of pituitary Superior hypophyseal artery 2 Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary. 3 In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation. GH, TSH, ACTH, FSH, LH, PRL Anterior lobe of pituitary © 2013 Pearson Education, Inc. Hypothalamic neurons synthesize GHRH, GHIH, TRH, CRH, GnRH, PIH. 1 When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. Hypophyseal portal system • Primary capillary plexus • Hypophyseal portal veins • Secondary capillary plexus A portal system is two capillary plexuses (beds) connected by veins. • Ok – Endocrinology – is a whole BRANCH of medicine, so at this point we have to pick and choose what to cover… otherwise we’d spend the rest of the year on this unit! • The next few slides aren’t in your book, they’re from a different Anatomy text, you don’t have to KNOW everything here, the “jist” of it is the chain of command… take pics if you wish! © 2013 Pearson Education, Inc. Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (2 of 4) © 2013 Pearson Education, Inc. Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (3 of 4) © 2013 Pearson Education, Inc. Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (4 of 4) © 2013 Pearson Education, Inc. Table 16.1 Pituitary Hormones: Summary of Regulation and Effects (1 of 4) © 2013 Pearson Education, Inc. Figure 16.8 Regulation of thyroid hormone secretion. Hypothalamus TRH Anterior pituitary TSH Thyroid gland Thyroid hormones Target cells © 2013 Pearson Education, Inc. Stimulates Inhibits Figure 16.9 The thyroid gland. Hyoid bone Thyroid cartilage Common carotid artery Inferior thyroid artery Trachea Epiglottis Colloid-filled follicles Follicular cells Superior thyroid artery Isthmus of thyroid gland Left subclavian artery Left lateral lobe of thyroid gland Aorta Parafollicular cells Gross anatomy of the thyroid gland, anterior view © 2013 Pearson Education, Inc. Photomicrograph of thyroid gland follicles (145x) Table 16.2 Major Effects of Thyroid Hormone (T4 and T3) in the Body (1 of 2) © 2013 Pearson Education, Inc. Table 16.2 Major Effects of Thyroid Hormone (T4 and T3) in the Body (2 of 2) © 2013 Pearson Education, Inc. Figure 16.11 Thyroid disorders. © 2013 Pearson Education, Inc. Parathyroid hormones • Parathyroid glands – 2 pairs embedded in the posterior surfaces of the thyroid gland • Chief cells – secrete parathyroid hormone • PTH causes increased calcium concentrations in body fluids (the opposite of Calcitonin – secreted by C cells in the thyroid – causes decreased calcium concentrations in body fluids) Figure 16.12 The parathyroid glands. Pharynx (posterior aspect) Capillary Thyroid gland Parathyroid glands Esophagus Trachea © 2013 Pearson Education, Inc. Parathyroid cells (secrete parathyroid hormone) Oxyphil cells The Adrenal Glands • Adrenal glands – 2 parts – Adrenal cortex – 3 zones that produce different corticosteroids, the outer zone produces mineralcorticoids, the middle zone produces glucorticoids and the inner zone produces androgens. – Adrenal medulla – produces 2 hormones, epinephrine (E, or adrenaline) and norepinephrine (NE, or noradrenaline) Adrenal Cortex • Three layers of cortex produce the different corticosteroids – Zona glomerulosa—mineralocorticoids – Zona fasciculata—glucocorticoids – Zona reticularis—gonadocorticoids © 2013 Pearson Education, Inc. Figure 16.14 Microscopic structure of the adrenal gland. Hormones secreted Capsule Zona glomerulosa Aldosterone Adrenal gland • Medulla • Cortex Cortex Zona fasciculata Cortisol and androgens Kidney Medulla Zona reticularis Adrenal medulla Drawing of the histology of the adrenal cortex and a portion of the adrenal medulla © 2013 Pearson Education, Inc. Epinephrine and norepinephrine Photomicrograph (115x) Mineralocorticoids • Regulate electrolytes (primarily Na+ and K+) in ECF – Importance of Na+: affects ECF volume, blood volume, blood pressure, levels of other ions – Importance of K+: sets RMP of cells • Aldosterone most potent mineralocorticoid – Stimulates Na+ reabsorption and water retention by kidneys; elimination of K+ © 2013 Pearson Education, Inc. Glucocorticoids • Keep blood glucose levels relatively constant • Maintain blood pressure by increasing action of vasoconstrictors • Cortisol (hydrocortisone) – Only one in significant amounts in humans • Cortisone • Corticosterone © 2013 Pearson Education, Inc. Glucocorticoids: Cortisol • Released in response to ACTH, patterns of eating and activity, and stress • Prime metabolic effect is gluconeogenesis—formation of glucose from fats and proteins – Promotes rises in blood glucose, fatty acids, and amino acids • "Saves" glucose for brain • Enhances vasoconstriction rise in blood pressure to quickly distribute nutrients to cells © 2013 Pearson Education, Inc. Androgens • Androgens – the adrenal cortex in both sexes produces small quantities of androgens – the sex hormones produced in large quantities by the testes in males • Converted to estrogens in the bloodstream • The importance of adrenal production in both sexes is unclear Adrenal Medulla • Medullary chromaffin cells synthesize epinephrine (80%) and norepinephrine (20%) • Effects – Vasoconstriction – Increased heart rate – Increased blood glucose levels – Blood diverted to brain, heart, and skeletal muscle © 2013 Pearson Education, Inc. Adrenal Medulla • Responses brief • Epinephrine stimulates metabolic activities, bronchial dilation, and blood flow to skeletal muscles and heart (involved in fight or flight response) • Norepinephrine influences peripheral vasoconstriction and blood pressure © 2013 Pearson Education, Inc. Pineal Gland • Secretes melatonin • 3 functions: – Inhibition of reproductive function (timing of sexual maturation) – Antioxidant activity – protect CNS neurons from free radicals – Establishment of day-night cycles of activity – Circadian rhythms © 2013 Pearson Education, Inc. Pancreas • Triangular gland partially behind stomach • Has both exocrine and endocrine cells – Acinar cells (exocrine) produce enzyme-rich juice for digestion – Pancreatic islets (islets of Langerhans) contain endocrine cells • Alpha () cells produce glucagon (hyperglycemic hormone) • Beta () cells produce insulin (hypoglycemic hormone) © 2013 Pearson Education, Inc. Figure 16.18 Photomicrograph of differentially stained pancreatic tissue. Pancreatic islet • (Glucagonproducing) cells • (Insulinproducing) cells Pancreatic acinar cells (exocrine) © 2013 Pearson Education, Inc. Glucagon • Major target—liver • Causes increased blood glucose levels • Effects – Glycogenolysis—breakdown of glycogen to glucose – Gluconeogenesis—synthesis of glucose from lactic acid and noncarbohydrates – Release of glucose to blood © 2013 Pearson Education, Inc. Insulin • Effects of insulin – Lowers blood glucose levels – Enhances membrane transport of glucose into fat and muscle cells – Inhibits glycogenolysis and gluconeogenesis – Participates in neuronal development and learning and memory • Not needed for glucose uptake in liver, kidney or brain © 2013 Pearson Education, Inc. Figure 16.19 Insulin and glucagon from the pancreas regulate blood glucose levels. Stimulates glucose uptake by cells Tissue cells Insulin Stimulates glycogen formationw Pancreas Glucose Glycogen Blood glucose falls to normal range. Liver Stimulus Blood glucose level Stimulus Blood glucose level Blood glucose rises to normal range. Pancreas Glucose Glycogen Liver © 2013 Pearson Education, Inc. Stimulates glycogen breakdown Glucagon Factors That Influence Insulin Release • • • • Elevated blood glucose levels – primary stimulus Rising blood levels of amino acids and fatty acids Release of acetylcholine by parasympathetic nerve fibers Hormones glucagon, epinephrine, growth hormone, thyroxine, glucocorticoids • Somatostatin; sympathetic nervous system © 2013 Pearson Education, Inc. Homeostatic Imbalances of Insulin • Diabetes mellitus (DM) – Due to hyposecretion (type 1) or hypoactivity (type 2) of insulin – Blood glucose levels remain high nausea higher blood glucose levels (fight or flight response) – Glycosuria – glucose spilled into urine – Fats used for cellular fuel lipidemia; if severe ketones (ketone bodies) from fatty acid metabolism ketonuria and ketoacidosis – Untreated ketoacidosis hyperpnea; disrupted heart activity and O2 transport; depression of nervous system coma and death possible © 2013 Pearson Education, Inc. Diabetes Mellitus: Signs • Three cardinal signs of DM – Polyuria—huge urine output • Glucose acts as osmotic diuretic – Polydipsia—excessive thirst • From water loss due to polyuria – Polyphagia—excessive hunger and food consumption • Cells cannot take up glucose; are "starving" © 2013 Pearson Education, Inc. Homeostatic Imbalances of Insulin • Hyperinsulinism: – Excessive insulin secretion – Causes hypoglycemia • Low blood glucose levels • Anxiety, nervousness, disorientation, unconsciousness, even death – Treated by sugar ingestion © 2013 Pearson Education, Inc. Ovaries and Placenta • Gonads produce steroid sex hormones – Same as those of adrenal cortex • Ovaries produce estrogens and progesterone – Estrogen • Maturation of reproductive organs • Appearance of secondary sexual characteristics • With progesterone, causes breast development and cyclic changes in uterine mucosa • Placenta secretes estrogens, progesterone, and human chorionic gonadotropin (hCG) © 2013 Pearson Education, Inc. Testes • Testes produce testosterone – Initiates maturation of male reproductive organs – Causes appearance of male secondary sexual characteristics and sex drive – Necessary for normal sperm production – Maintains reproductive organs in functional state © 2013 Pearson Education, Inc. Other Hormone-producing Structures • Adipose tissue – Leptin – appetite control; stimulates increased energy expenditure – Resistin – insulin antagonist – Adiponectin – enhances sensitivity to insulin © 2013 Pearson Education, Inc. Other Hormone-producing Structures • Enteroendocrine cells of gastrointestinal tract – Gastrin stimulates release of HCl – Secretin stimulates liver and pancreas – Cholecystokinin stimulates pancreas, gallbladder, and hepatopancreatic sphincter – Serotonin acts as paracrine © 2013 Pearson Education, Inc. Other Hormone-producing Structures • Heart – Atrial natriuretic peptide (ANP) decreases blood Na+ concentration, therefore blood pressure and blood volume • Kidneys – Erythropoietin signals production of red blood cells – Renin initiates the renin-angiotensin-aldosterone mechanism © 2013 Pearson Education, Inc. Other Hormone-producing Structures • Thymus – Large in infants and children; shrinks as age – Thymulin, thymopoietins, and thymosins • May be involved in normal development of T lymphocytes in immune response • Classified as hormones; act as paracrines © 2013 Pearson Education, Inc.