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Essentials of Human Anatomy & Physiology Seventh Edition Elaine N. Marieb Chapter 9 The Endocrine System Slides 9.1 – 9.22 Lecture Slides in PowerPoint Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Endocrine System Second messenger system of the body Uses chemical messages (hormones) that are released into the blood Hormones control several major processes Reproduction Growth and development Mobilization of body defenses Maintenance of much of homeostasis Regulation of metabolism Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Hormone Overview Hormones are produced by specialized cells Cells secrete hormones into extracellular fluids (blood) Blood transfers hormones to target sites These hormones regulate the activity of other cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide The Chemistry of Hormones Amino acid-based hormones Proteins Peptides Amines Steroids – made from cholesterol Prostaglandins (local hormones) – made from highly active lipids in cell membranes. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Mechanisms of Hormone Action Hormones affect only certain tissues or organs (target cells or organs) Target cells must have specific protein receptors Hormone binding influences the working of the cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Effects Caused by Hormones Hormone means “to arouse”. They alter cellular activity by increasing or decreasing a normal cellular process. 1. Changes in plasma membrane permeability or electrical state 2. Synthesis of proteins, such as enzymes 3. Activation or inactivation of enzymes 4. Stimulation of mitosis 5. Promotion of secretory activity Slide Steroid Hormone Action Diffuse through the plasma membrane of target cells Enter the nucleus Bind to a specific protein within the nucleus Bind to specific sites on the cell’s DNA Activate genes that result in synthesis of new proteins Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Steroid hormone Extracellular fluid Plasma membrane 1 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. Cytoplasm Receptor protein Receptorhormone complex Nucleus Figure 16.3, step 1 Steroid hormone Extracellular fluid Plasma membrane 1 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. Cytoplasm Receptor protein Receptorhormone complex 2 The receptor- Nucleus hormone complex enters the nucleus. Figure 16.3, step 2 Steroid hormone Extracellular fluid Plasma membrane 1 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. Cytoplasm Receptor protein Receptorhormone complex 2 The receptor- Nucleus Hormone response elements DNA hormone complex enters the nucleus. 3 The receptor- hormone complex binds a hormone response element (a specific DNA sequence). Figure 16.3, step 3 Steroid hormone Extracellular fluid Plasma membrane 1 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. Cytoplasm Receptor protein Receptorhormone complex 2 The receptor- Nucleus Hormone response elements DNA mRNA hormone complex enters the nucleus. 3 The receptor- hormone complex binds a hormone response element (a specific DNA sequence). 4 Binding initiates transcription of the gene to mRNA. Figure 16.3, step 4 Steroid hormone Plasma membrane Extracellular fluid 1 The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. Cytoplasm Receptor protein Receptorhormone complex 2 The receptor- Nucleus Hormone response elements DNA mRNA hormone complex enters the nucleus. 3 The receptor- hormone complex binds a hormone response element (a specific DNA sequence). 4 Binding initiates transcription of the gene to mRNA. 5 The mRNA directs protein synthesis. New protein Figure 16.3, step 5 Steroid Hormone Action Figure 9.1a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Nonsteroid Hormone Action Hormone binds to a membrane receptor Hormone does not enter the cell Sets off a series of reactions that activates an enzyme Catalyzes a reaction that produces a second messenger molecule Oversees additional intracellular changes to promote a specific response Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 1 Hormone (1st messenger) Extracellular fluid binds receptor. Receptor Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin Cytoplasm Figure 16.2, step 1 1 Hormone (1st messenger) Extracellular fluid binds receptor. G protein (GS) Receptor GDP Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin 2 Receptor activates G protein (GS). Cytoplasm Figure 16.2, step 2 1 Hormone (1st messenger) binds receptor. Adenylate cyclase Extracellular fluid G protein (GS) Receptor GDP Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin 2 Receptor activates G protein (GS). 3 G protein activates adenylate cyclase. Cytoplasm Figure 16.2, step 3 1 Hormone (1st messenger) binds receptor. Adenylate cyclase Extracellular fluid G protein (GS) Receptor GDP Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin 2 Receptor activates G protein (GS). 3 G protein activates adenylate cyclase. 4 Adenylate cyclase converts ATP to cAMP (2nd messenger). Cytoplasm Figure 16.2, step 4 1 Hormone (1st messenger) binds receptor. Adenylate cyclase Extracellular fluid G protein (GS) 5 cAMP acti- vates protein kinases. Receptor GDP Hormones that act via cAMP mechanisms: Epinephrine ACTH FSH LH Glucagon PTH TSH Calcitonin 2 Receptor activates G protein (GS). 3 G protein activates adenylate cyclase. 4 Adenylate cyclase converts ATP to cAMP (2nd messenger). Active protein kinase Triggers responses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.) Cytoplasm Inactive protein kinase Figure 16.2, step 5 Nonsteroid Hormone Action Animation Figure 9.1b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Control of Hormone Release Hormone levels in the blood are maintained by negative feedback A stimulus or low hormone levels in the blood triggers the release of more hormone Hormone release stops once an appropriate level in the blood is reached Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Overview of the Endocrine System •Control of Endocrine Secretion • Humoral (fluid) stimuli • E.g., blood level of Ca2+ directly controls parathyroid hormone and calcitonin release • Hormonal stimuli • E.g., thyroid stimulating hormone triggers thyroid hormone release • Neural stimuli • E.g., epinephrine release from adrenal gland Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Stimuli of Endocrine Glands Endocrine glands are activated by other hormones – hormonal stimulus Figure 9.2a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Humoral Stimuli of Endocrine Glands Changing blood levels of certain ions stimulate hormone release – humoral stimuli Figure 9.2b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Neural Stimuli of Endocrine Glands Nerve impulses stimulate hormone release – neural stimuli Most are under control of the sympathetic nervous system Figure 9.2c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Nervous System Modulation • The nervous system modifies the stimulation of endocrine glands and their negative feedback mechanisms • Example: under severe stress, the hypothalamus and the sympathetic nervous system are activated • As a result, body glucose levels rise Location of Major Endrocrine Organs Figure 9.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide • Pituitary Gland • Small, pea size gland. Very mighty gland, that is actually two glands in one, the anterior and posterior pituitary. • Buried deep in the cranial cavity in a depression in the sphenoid bone called the sella tursica. • The pituitary gland (hypophysis) has two major lobes 1. Anterior pituitary (lobe) • Glandular tissue 2. Posterior pituitary (lobe): • Nervous tissue • Anterior Lobe: • Releasing and inhibiting hormones are carried to the anterior lobe from the hypothalamus to control the release of the many hormones it secretes. Hypothalamus Hypothalamic neuron cell bodies Superior hypophyseal artery Hypophyseal portal system • Primary capillary plexus • Hypophyseal portal veins • Secondary capillary plexus Anterior lobe of pituitary TSH, FSH, LH, ACTH, GH, PRL 1 When appropriately stimulated, hypothalamic neurons secrete releasing and inhibiting hormones into the primary capillary plexus. 2 Hypothalamic hormones travel through the portal veins to the anterior pituitary where they stimulate or inhibit release of hormones from the anterior pituitary. 3 Anterior pituitary hormones are secreted into the secondary capillary plexus. (b) Relationship between the anterior pituitary and the hypothalamus Figure 16.5b • Called the master gland because it exerts control over the thyroid gland, adrenal cortex, ovarian follicles, and the corpus luteum. • Tropic hormones – hormones whose target organs are other endocrine glands. Anterior Pituitary Hormones • Growth hormone (GH) • Thyroid-stimulating hormone (TSH) or thyrotropin • Adrenocorticotropic hormone (ACTH) • Follicle-stimulating hormone (FSH) • Luteinizing hormone (LH) • Prolactin (PRL) • Growth hormone • Speeds up the absorption of amino acids which will be used to produce new proteins. Accelerates fat breakdown for energy use and slows glucose breakdown. • Major effects directed to the growth of skeletal muscles and long bones of the body. Homeostatic Imbalances of Growth Hormone • Hypersecretion • In children results in gigantism • In adults results in acromegaly • Hyposecretion • In children results in pituitary dwarfism Gigantism Dwarfism video video video • Prolactin • During pregnancy stimulates the breast development for milk production, then after delivery, stimulates breasts to secrete milk. • Adrenocorticotropic Hormone (ACTH) • Stimulates the adrenal cortex to increase in size and to secrete its hormone, cortisol (hydrocortizone). • Thyroid Stimulating Hormone (TSH) • Stimulates the thyroid gland to secrete its hormone, thyroxine. • Follicle-stimulating hormone (FSH) • Stimulates the ovarian follicles to develop. As the follicles mature produce estrogen, and eggs are readied for ovulation. • In the male FSH stimulates sperm development. • Luteinizing hormone • Triggers ovulation. Causes the ruptured follicle to produce progesterone. • In the male it stimulates interstitial cells to secrete testosterone. Pituitary-Hypothalamus Relationship • Hypothalamus • Actually produces ADH and Oxytocin by specialized neurons, which then passes down along the axons into the posterior pituitary gland. Pituitary-Hypothalamus Relationship • Also produces substances called releasing and inhibiting hormones. These are produced in the hypothalamus then go directly to the anterior pituitary by way of specialized blood capillaries. Pituitary-Hypothalamus Relationship • The combined nervous and endocrine functions of the hypothalamus help it to play a dominant role in regulating many body functions, like temperature, appetite, and thirst. • Posterior lobe • It is a downgrowth of the hypothalamus. Nuclei in the hypothalamus produce 2 hormones (oxytocin and antidiuretic hormone (ADH)) that travel down the axons to the posterior pituitary, where they are stored in the axon terminals there. 1 Hypothalamic Paraventricular nucleus Supraoptic nucleus Optic chiasma Infundibulum (connecting stalk) Hypothalamichypophyseal tract Axon terminals Posterior lobe of pituitary Hypothalamus neurons synthesize oxytocin and ADH. 2 Oxytocin and ADH are Inferior hypophyseal artery transported along the hypothalamic-hypophyseal tract to the posterior pituitary. 3 Oxytocin and ADH are stored in axon terminals in the posterior pituitary. 4 Oxytocin and ADH are Oxytocin ADH released into the blood when hypothalamic neurons fire. (a) Relationship between the posterior pituitary and the hypothalamus Figure 16.5a • Oxytocin • Stimulates the uterus to contract during labor. • Causes the glandular cells in breast to release milk into the ducts. • Posterior Pituitary • Antidiuretic hormone (ADH) • accelerates the reabsorption of water from urine in the kidney tubules to the blood. • Therefore its purpose is to help keep fluid in the body and to decrease urine volume. Hyposecretion of ADH results in “diabetes insipidus” a condition in which large volumes of urine are formed. Thyroid Gland • Consists of two lateral lobes connected by a median mass called the isthmus. Figure 16.8 • Thyroid Gland • Secretes two thyroid hormones T4 and T3. T4 is more abundant but T3 is more potent. • Both hormones require iodine connected to peptide groups as part of their structure. Thyroid Hormone • Major metabolic hormone • Increases metabolic rate and heat production • Plays a role in • Maintenance of blood pressure • Regulation of tissue growth • Development of skeletal and nervous systems • Reproductive capabilities • Hyperthyroidism • Generally results from tumor of thyroid gland. • increases metabolic rate of all cells, weight loss, intolerance to heat, rapid heart rate, irritable, nervous, increased appetite, protrusion of eyeballs (exopthalmos). Called Graves Disease. Figure 16.10 • Hypothyroidism • decreases metabolic rate. • Lack of iodine results in lower thyroxine levels which causes the pituitary to increase TSH. This calls for more thyroxine from the thyroid, so the thyroid gland enlarges (called a goiter), but without iodine it can only make the peptide part of the molecule. • Hypothyroidism in the young causes cretinism; retarded growth, sexual development, and mental retardation. In adults causes myxedema; decreased mental and physical vigor, weight gain, loss of hair, and swelling, low body temperature (feels cold), dry skin. • Also secretes the hormone calcitonin. Calcitonin decreases the concentration of calcium in the blood by causing it to be deposited in the bones, preventing hypercalcemia. • Parathyroid Glands • 4 small glands located on the back of the thyroid gland. • Secretes parathyroid hormone (PTH). • The most important regulator of blood calcium ion concentration. • Does the opposite of calcitonin. It will increase the concentration of calcium in the blood by increasing osteoclastic activity which breaks down bone matrix releasing calcium into the blood. • If calcium levels fall too low, muscles go into uncontrolable spasms called tetany. • Hyperparathyroidism causes excess PTH production, which causes excess osteoclastic activity in the bone, leaving the person with severe osteoporosis. • Adrenal Glands • Sits on top of each kidney. • Two separate glands • Adrenal cortex -outer part • Adrenal medulla - inner part • Adrenal Cortex • Hormones secreted by the cortex are called corticoids. • 3 layers to cortex from outer to inner… »Outer zone »Middle zone »Inner zone • Outer zone secretes mineralocorticoids, chiefly aldosterone, which increases sodium and decreases potassium in the blood. Since water follows sodium aldosterone regulated both water and electrolyte balance. • Middle zone secretes glucocorticoids, chiefly cortisol or cortisone. Resists long-term stressors by increasing blood glucose (gluconeogenesis). • Cortisol also helps maintain normal blood pressure. • It also has an antiinflammatory effect, antiimmunity effect, and antiallergy effect. • Stress causes the adrenal cortex to increase secretion of glucocorticoids. Cushing’s Syndrome • Excessive cortisol production leads to swollen “moon face” and a “buffalo hump” of fat on the upper back. Also results in high blood pressure, hyperglycemia and severe depression of the immune system. Figure 16.15 Addison’s Disease • Hyposecretion of all the adrenal cortex hormones. Characterized by a strange bronze tone of the skin. Electrolyte and water loss, muscle weakness, suppressed immune system, lessened ability to cope with stress. • Inner zone secretes small amounts of sex hormomes, chiefly testosterone. These are weak and insignificant functionally in the male, but, stimulates the female sex drive in the female. • Adrenal Medulla • Secretes epinephrin (adrenalin) and norepinephrin (collectively called catecholamines). Chief hormones that respond to stress quickly. Fight or flight response. • Adrenal medulla stimulated by sympathetic nerve fibers. When stimulated it literally squirts epinephrine and norepinephrine into the blood stream to deal with brief, short-term stressful situations. • Both an endocrine and exocrine gland. • Pancreatic Islets • or islets of Langerhans are little clumps of cells within the pancreas. Two types, alpha and beta cells. • Alpha cells secrete hormone called glucagon, beta cells secrete insulin. • Glucagon accelerates process called gycogenolysis, which breaks glycogen into glucose, which raises blood glucose levels. • Insulin decreases blood glucose concentrations, by accelerating its movement out of the blood and into the cells. • Hypoglycemia - lower than normal glucose in the blood. • Hyperglycemia - higher than normal glucose in the blood. Stimulates glucose uptake by cells Tissue cells Insulin Pancreas Stimulates glycogen formation Glucose Glycogen Blood glucose falls to normal range. Liver Stimulus Blood glucose level Stimulus Blood glucose level Blood glucose rises to normal range. Pancreas Liver Glucose Glycogen Stimulates glycogen Glucagon breakdown Figure 16.18 • Diabetes melitis • Type I - Pancreas secrete too little insulin so glucose stays in the blood instead of entering the cells, creating high blood glucose levels. • Type II - (insulin independent) results from abnormality of the insulin receptors on the cell membranes of cells. Also results in high glucose levels. • Glucose that spills out into the urine is called glycosuria. • Pineal Gland • Small pine-cone shaped gland in the roof of the third ventricle. Secretes melatonin. Pineal gland sometimes called the “third eye” because... • … it receives sensory info from the optic nerves. It uses this info regarding changing light levels to adjust the levels of melatonin, high at night and low during the day. • Melatonin therefore might regulate the bodies internal clock. • Thymus • Hormone thymosin that plays an important role in the development and function of the bodies immune system. • Female Sex Glands • Ovaries • Ovarian follicles secrete estrogen, which is involved in the development of the secondary female sex characteristics and initiation of the menstrual cycle. • The corpus luteum mainly secretes progesterone but some estrogen also. • Male Sex Glands • The interstitial cells of the testes produce testosterone, the masculinizing hormone. Causes development of male secondary sex characteristics. Other Hormone-Producing Tissues and Organs Parts of the small intestine Parts of the stomach Kidneys Heart Many other areas have scattered endocrine cells Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide • Placenta • a temporary endocrine gland. During pregnancy it produces chorionic gonadotropins. Also produces estrogen and progesterone. Endocrine Function of the Placenta Produces hormones that maintain the pregnancy Some hormones play a part in the delivery of the baby Produces HCG in addition to estrogen, progesterone, and other hormones Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Developmental Aspects of the Endocrine System Most endocrine organs operate smoothly until old age Menopause is brought about by lack of efficiency of the ovaries Problems associated with reduced estrogen are common Growth hormone production declines with age Many endocrine glands decrease output with age Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide