Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College Chapter 9 The Endocrine System 2015 Pearson Education, Inc. The Endocrine System Second controlling system of the body Nervous system is the fast-control system Uses chemical messengers (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 2015 Pearson Education, Inc. Hormone Overview Hormones are produced by specialized cells Cells secrete hormones into extracellular fluids Blood transfers hormones to target sites These hormones regulate the activity of other cells Endocrinology is the scientific study of hormones and endocrine organs 2015 Pearson Education, Inc. The Chemistry of Hormones Hormones are classified chemically as Amino acidbased, which includes: Proteins Peptides Amines Steroidsmade from cholesterol Prostaglandinsmade from highly active lipids that act as local hormones 2015 Pearson Education, Inc. Hormone Action Hormones affect only certain tissues or organs (target cells or target organs) Target cells must have specific protein receptors Hormone binding alters cellular activity 2015 Pearson Education, Inc. Hormone Action Hormones arouse cells, or alter cellular activity. Typically, one or more of the following occurs: 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 2015 Pearson Education, Inc. The Chemistry of Hormones Hormones act by two mechanisms: 1.Direct gene activation 2.Second-messenger system 2015 Pearson Education, Inc. Direct Gene Activation (Steroid Hormone Action) 1.Steroid hormones diffuse through the plasma membrane of target cells 2.Steroid hormones enter the nucleus 3.Steroid hormones bind to a specific protein within the nucleus 4.Hormone-receptor complex binds to specific sites on the cells DNA 5.Certain genes are activated that result in 6.Synthesis of new proteins 2015 Pearson Education, Inc. Figure 9.1a Mechanisms of hormone action. Steroid hormone Cytoplasm Nucleus Receptor protein Hormone-receptor complex DNA mRNA New protein Plasma membrane of target cell 1 (a) Steroid hormone action Slide 1 Second-Messenger System (Nonsteroid Hormone Action) 1.Hormone (first messenger) binds to a membrane receptor 2.Activated receptor sets off a series of reactions that activates an enzyme 3.Enzyme catalyzes a reaction that produces a second-messenger molecule (such as cyclic AMP, or cAMP) 4.Oversees additional intracellular changes to promote a specific response in the target cell 2015 Pearson Education, Inc. Figure 9.1b Mechanisms of hormone action. (b) Nonsteroid hormone action Plasma membrane of target cell Receptor protein Nonsteroid hormone (first messenger) Cytoplasm Enzyme ATP cAMP Second messenger Effect on cellular function, such as glycogen breakdown Slide 1 Control of Hormone Release Hormone levels in the blood are maintained mostly 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 2015 Pearson Education, Inc. Endocrine Gland Stimuli The stimuli that activate endocrine glands fall into three major categories: 1.Hormonal 2.Humoral 3.Neural 2015 Pearson Education, Inc. Hormonal Stimuli of Endocrine Glands Most common stimulus Endocrine organs are activated by other hormones Example: Anterior pituitary hormones travel to target glands, such as the thyroid gland, to prompt the release of a particular hormone, such as thyroid hormone 2015 Pearson Education, Inc. Figure 9.2a Endocrine gland stimuli. (a) Hormonal stimulus The hypothalamus secretes hormones that Hypothalamus 1 stimulate the anterior pituitary gland to secrete hormones that Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (testis) stimulate other endocrine glands to secrete hormones 2 3 Humoral Stimuli of Endocrine Glands Changing blood levels of certain ions and nutrients stimulate hormone release Humoral indicates various body fluids, such as blood and bile Examples: Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels Insulin is produced in response to changing levels of blood glucose levels 2015 Pearson Education, Inc. Figure 9.2b Endocrine gland stimuli. (b) Humoral stimulus Capillary blood contains low concentration of Ca 2+, which stimulates Capillary (low Ca 2+ in blood) Thyroid gland (posterior view) Parathyroid glands Parathyroid glands PTH secretion of parathyroid hormone (PTH) by parathyroid glands) 1 2 Neural Stimuli of Endocrine Glands Nerve impulses stimulate hormone release Most are under the control of the sympathetic nervous system Examples: The release of norepinephrine and epinephrine by the adrenal medulla 2015 Pearson Education, Inc. Figure 9.2c Endocrine gland stimuli. (c) Neural stimulus Preganglionic sympathetic fiber stimulates adrenal medulla cells CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary to secrete catecholamines (epinephrine and norepinephrine) 1 2 Major Endocrine Organs Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pineal gland Thymus gland Pancreas Gonads (ovaries and testes) Hypothalamus 2015 Pearson Education, Inc. Figure 9.3 Location of the major endocrine organs of the body. Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Major Endocrine Organs Some glands are purely endocrine Anterior pituitary, thyroid, adrenals, parathyroids Endocrine glands are ductless glands Hormones are released directly into blood or lymph Other glands are mixed glands, with both endocrine and exocrine functions (pancreas, gonads) 2015 Pearson Education, Inc. Pituitary Gland and Hypothalamus Pituitary gland is the size of a pea Hangs by a stalk from the hypothalamus in the brain Protected by the sphenoid bone Has two functional lobes Anterior pituitaryglandular tissue Posterior pituitarynervous tissue Often called the master endocrine gland 2015 Pearson Education, Inc. Pituitary Gland and Hypothalamus Hypothalamus produces releasing and inhibiting hormones These hormones are released into portal circulation, which connects hypothalamus to anterior pituitary Hypothalamus also makes two hormones: oxytocin and antidiuretic hormone Carried to posterior pituitary via neurosecretory cells for storage 2015 Pearson Education, Inc. Figure 9.4 Hormones released by the posterior lobe of the pituitary and their target organs. Optic chiasma Axon terminals Anterior lobe of the pituitary Venous drainage Capillary bed Posterior lobe Arterial blood supply Hypothalamus Hypothalamic neurosecretory cells ADHOxytocin Kidney tubulesMammary glands Uterine muscles Posterior Pituitary and Hypothalamic Hormones Oxytocin Stimulates contractions of the uterus during labor, sexual relations, and breastfeeding Causes milk ejection (let-down reflex) in a breastfeeding woman 2015 Pearson Education, Inc. Posterior Pituitary and Hypothalamic Hormones Antidiuretic hormone (ADH) Inhibits urine production (diuresis) by promoting water reabsorption by the kidneys In large amounts, causes vasoconstriction of arterioles, leading to increased blood pressure (the reason why ADH is known as vasopressin) Alcohol inhibits ADH secretion Diabetes insipidus results from ADH hyposecretion 2015 Pearson Education, Inc. Hormones of the Anterior Pituitary Six anterior pituitary hormones Two affect nonendocrine targets: 1.Growth hormone 2.Prolactin 2015 Pearson Education, Inc. Hormones of the Anterior Pituitary Four stimulate other endocrine glands to release hormones (tropic hormones): 1.Thyroid-stimulating hormone (thyrotropic hormone) 2.Adrenocorticotropic hormone 3.Follicle-stimulating hormone 4.Luteinizing hormone 2015 Pearson Education, Inc. Hormones of the Anterior Pituitary Characteristics of all anterior pituitary hormones Protein (or peptides) structure Act through second-messenger systems Regulated by hormonal stimuli Regulated mostly by negative feedback 2015 Pearson Education, Inc. Figure 9.5 Hormones of the anterior pituitary and their major target organs. Posterior pituitary Adrenocorticotropic hormone (ACTH) Adrenal cortexThyrotropic hormone (TH) Thyroid Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Testes or ovaries Mammary glands Prolactin (PRL)Bones and muscles Growth hormone (GH) Hypophyseal portal system Anterior pituitary Releasing hormones secreted into portal circulation Hypothalamus Hormones of the Anterior Pituitary Growth hormone (GH) General metabolic hormone Major effects are directed to growth of skeletal muscles and long bones Plays a role in determining final body size Causes amino acids to be built into proteins Causes fats to be broken down for a source of energy 2015 Pearson Education, Inc. Hormones of the Anterior Pituitary Growth hormone (GH) disorders Pituitary dwarfism results from hyposecretion of GH during childhood Gigantism results from hypersecretion of GH during childhood Acromegaly results from hypersecretion of GH during adulthood 2015 Pearson Education, Inc. Figure 9.6 Disorders of pituitary growth hormone. This individual exhibiting gigantism (right) stands 8 feet, 1 inch tall. The pituitary dwarf (left) is 2 feet, 5.37 inches tall. Hormones of the Anterior Pituitary Prolactin (PRL) Stimulates and maintains milk production following childbirth Function in males is unknown Adrenocorticotropic hormone (ACTH) Regulates endocrine activity of the adrenal cortex 2015 Pearson Education, Inc. Hormones of the Anterior Pituitary Thyrotropic hormone (TH), also called thyroid- stimulating hormone (TSH) Influences growth and activity of the thyroid gland 2015 Pearson Education, Inc. Hormones of the Anterior Pituitary Gonadotropic hormones Regulate hormonal activity of the gonads Follicle-stimulating hormone (FSH) Stimulates follicle development in ovaries Stimulates sperm development in testes Luteinizing hormone (LH) Triggers ovulation of an egg in females Stimulates testosterone production in males 2015 Pearson Education, Inc. Thyroid Gland Found at the base of the throat Consists of two lobes and a connecting isthmus Produces two hormones: 1.Thyroid hormone 2.Calcitonin 2015 Pearson Education, Inc. Figure 9.7a The thyroid gland. Isthmus of thyroid gland Thyroid cartilage Common carotid artery Trachea Brachiocephalic artery Aorta (a) Gross anatomy of the thyroid gland, anterior view Epiglottis Left subclavian artery Left lobe of thyroid gland Thyroid Gland Thyroid hormone Major metabolic hormone Controls rate of oxidation of glucose to supply body heat and chemical energy Needed for tissue growth and development Composed of two active iodine-containing hormones Thyroxine (T 4 )secreted by thyroid follicles Triiodothyronine (T 3 )conversion of T 4 at target tissues 2015 Pearson Education, Inc. Figure 9.7b The thyroid gland. (b) Photomicrograph of thyroid gland follicles (380) Parafollicular cells Colloid-filled follicles Follicle cells Thyroid Gland Thyroid hormone disorders Goiters Thyroid gland enlarges because of lack of iodine Salt is iodized to prevent goiters Cretinism Caused by hyposecretion of thyroxine Results in dwarfism during childhood 2015 Pearson Education, Inc. Figure 9.8 Woman with an enlarged thyroid (goiter). Thyroid Gland Thyroid hormone disorders (continued) Myxedema Caused by hypothyroidism in adults Results in physical and mental sluggishness Graves disease Caused by hyperthyroidism Results in increased metabolism, heat intolerance, rapid heartbeat, weight loss, and exophthalmos 2015 Pearson Education, Inc. Figure 9.9 The exophthalmos of Graves disease. Thyroid Gland Calcitonin Decreases blood calcium levels by causing calcium deposition on bone Antagonistic to parathyroid hormone Produced by parafollicular cells found between the follicles 2015 Pearson Education, Inc. Figure 9.7b The thyroid gland. (b) Photomicrograph of thyroid gland follicles (380) Parafollicular cells Colloid-filled follicles Follicle cells Parathyroid Glands Tiny masses on the posterior of the thyroid Secrete parathyroid hormone (PTH) Stimulates osteoclasts to remove calcium from bone Hypercalcemic hormone (increases blood calcium levels) Stimulates the kidneys and intestine to absorb more calcium 2015 Pearson Education, Inc. Figure 9.10 Hormonal controls of ionic calcium levels in the blood. Parathyroid glands Thyroid gland Parathyroid glands release parathyroid hormone (PTH). PTH Stimulus Falling blood Ca 2+ levels BALANCE IMBALANCE Calcitonin stimulates calcium salt deposit in bone. Thyroid gland releases calcitonin. Calcitonin IMBALANCE BALANCE Stimulus Rising blood Ca 2+ levels Osteoclasts degrade bone matrix and release Ca 2+ into blood. Calcium homeostasis of blood: 911 mg/100 ml Adrenal Glands Sit on top of the kidneys Two regions: 1.Adrenal cortexouter glandular region has three layers that produce corticosteroids Mineralocorticoids are secreted by outermost layer Glucocorticoids are secreted by middle layer Sex hormones are secreted by innermost layer 2.Adrenal medullainner neural tissue region 2015 Pearson Education, Inc. Figure 9.11 Microscopic structure of the adrenal gland. Kidney Adrenal gland Adrenal gland Medulla Cortex Kidney Cortex Medulla Adrenal cortex Adrenal medulla Sex hormone secreting area Glucocorticoid- secreting area Mineralocorticoid- secreting area Capsule Hormones of the Adrenal Cortex Mineralocorticoids (mainly aldosterone) Produced in outer adrenal cortex Regulate mineral content in blood, particularly sodium and potassium ions Regulate water and electrolyte balance Target organ is the kidney 2015 Pearson Education, Inc. Hormones of the Adrenal Cortex Release of aldosterone is stimulated by: Humoral factors (fewer sodium ions or too many potassium ions in the blood) Hormonal stimulation (ACTH) Renin and angiotensin II in response to a drop in blood pressure Aldosterone production is inhibited by atrial natriuretic peptide (ANP), a hormone produced by the heart when blood pressure is too high 2015 Pearson Education, Inc. Figure 9.12 Major mechanisms controlling aldosterone release from the adrenal cortex. Kidney Decreased Na + or increased K + in blood Decreased blood volume and/or blood pressure Stress Hypothalamus Corticotropin- releasing hormone Anterior pituitary ACTH Increased blood pressure or blood volume Heart Renin Indirect stimulating effect via angiotensin Angiotensin II Atrial natriuretic peptide (ANP) Inhibitory effect Direct stimulating effect Mineralocorticoid- producing part of adrenal cortex Enhanced secretion of aldosterone targets kidney tubules Increased absorption of Na + and water; increased K + excretion Increased blood volume and blood pressure Hormones of the Adrenal Cortex Glucocorticoids (including cortisone and cortisol) Produced by middle layer of adrenal cortex Promote normal cell metabolism Help resist long-term stressors by increasing blood glucose levels (hyperglycemic hormone) Anti-inflammatory properties Released in response to increased blood levels of ACTH 2015 Pearson Education, Inc. Hormones of the Adrenal Cortex Sex hormones Produced in the inner layer of the adrenal cortex Small amounts are made throughout life Mostly androgens (male sex hormones) are made, but some estrogens (female sex hormones) are also formed 2015 Pearson Education, Inc. Adrenal Glands Adrenal cortex disorders Addisons disease Results from hyposecretion of all adrenal cortex hormones Bronze skin tone, muscle weakness, burnout, susceptibility to infection Hyperaldosteronism May result from an ACTH-releasing tumor Excess water and sodium are retained, leading to high blood pressure and edema 2015 Pearson Education, Inc. Adrenal Glands Adrenal cortex disorders (continued) Cushings syndrome Results from a tumor in the middle cortical area of the adrenal cortex Moon face, buffalo hump on the upper back, high blood pressure, hyperglycemia, weakening of bones, depression Masculinization Results from hypersecretion of sex hormones Beard and male distribution of hair growth 2015 Pearson Education, Inc. Hormones of the Adrenal Medulla Produces two similar hormones: (catecholamines) 1.Epinephrine (adrenaline) 2.Norepinephrine (noradrenaline) These hormones prepare the body to deal with short-term stress (fight or flight) by: Increasing heart rate, blood pressure, blood glucose levels Dilating small passageways of lungs 2015 Pearson Education, Inc. Figure 9.11 Microscopic structure of the adrenal gland. Kidney Adrenal gland Adrenal gland Medulla Cortex Kidney Cortex Medulla Adrenal cortex Adrenal medulla Sex hormone secreting area Glucocorticoid- secreting area Mineralocorticoid- secreting area Capsule 2015 Pearson Education, Inc. Figure 9.13 Roles of the hypothalamus, adrenal medulla, and adrenal cortex in the stress response. Hypothalamus Short termMore prolonged Spinal cord Nerve impulses Preganglionic sympathetic fibers Adrenal medulla Short-term stress response Catecholamines (epinephrine and norepinephrine) Increased heart rate Increased blood pressure Liver converts glycogen to glucose and releases glucose to blood Dilation of bronchioles Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity Increased metabolic rate Stress Releasing hormones Corticotropic cells of anterior pituitary ACTH Adrenal cortex MineralocorticoidsGlucocorticoids Long-term stress response Retention of sodium and water by kidneys Increased blood volume and blood pressure Proteins and fats converted to glucose or broken down for energy Increased blood sugar Suppression of immune system Pancreatic Islets Pancreas Located in the abdomen, close to stomach Mixed gland, with both endocrine and exocrine functions The pancreatic islets produce hormones Insulinproduced by beta cells Glucagonproduced by alpha cells These hormones are antagonists that maintain blood sugar homeostasis 2015 Pearson Education, Inc. Figure 9.14a Pancreatic tissue. Stomach Pancreas (a) 2015 Pearson Education, Inc. Figure 9.14b Pancreatic tissue. (b) Pancreatic islets Exocrine cells of pancreas 2015 Pearson Education, Inc. Figure 9.14c Pancreatic tissue. (c) Cord of beta () cells secreting insulin into capillaries Capillaries Exocrine cells of pancreas Alpha () cells Pancreatic Islets Insulin Released when blood glucose levels are high Increases the rate of glucose uptake and metabolism by body cells Glucagon Released when blood glucose levels are low Stimulates the liver to release glucose to blood, thus increasing blood glucose levels 2015 Pearson Education, Inc. Homeostatic Imbalance Diabetes mellitus Occurs in the absence of insulin Blood sugar levels increase dramatically Blood glucose is lost in the urine; water follows Three cardinal signs: 1.Polyuria 2.Polydipsia 3.Polyphagia 2015 Pearson Education, Inc. Figure 9.15 Regulation of blood glucose levels by a negative feedback mechanism involving pancreatic hormones. IMBALANCE Stimulus IMBALANCE BALANCE: Normal blood glucose level (about 90 mg/100 ml) Blood glucose level (e.g., after eating four jelly doughnuts) Stimulus Blood glucose level (e.g., after skipping a meal) Insulin Pancreas Tissue cells GlucoseGlycogen Uptake of glucose from blood is enhanced in most body cells Blood glucose falls to homeostatic set point; stimulus for insulin release diminishes Liver takes up glucose and stores as glycogen Insulin-secreting cells of the pancreas activated; release insulin into the blood Elevated blood sugar level Blood glucose rises to homeostatic set point; stimulus for glucagon release diminishes Liver breaks down glycogen stores and releases glucose to the blood GlucoseGlycogen Liver Glucagon Low blood sugar level Glucagon-releasing cells of pancreas activated; release glucagon into blood Pineal Gland Located posterior to the third ventricle of the brain Secretes melatonin Helps establish the bodys sleep/wake cycles as well as biological rhythms Believed to coordinate the hormones of fertility in humans 2015 Pearson Education, Inc. Figure 9.3 Location of the major endocrine organs of the body. Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Thymus Gland Located posterior to the sternum Largest in infants and children Produces thymosin Matures some types of white blood cells Important in developing the immune system 2015 Pearson Education, Inc. Gonads Ovaries Produce eggs Produce two groups of steroid hormones: 1.Estrogens 2.Progesterone Testes Produce sperm Produce androgens, such as testosterone 2015 Pearson Education, Inc. Figure 9.3 Location of the major endocrine organs of the body. Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Hormones of the Ovaries Estrogens Stimulate the development of secondary female characteristics Mature female reproductive organs With progesterone, estrogens also Promote breast development Regulate menstrual cycle 2015 Pearson Education, Inc. Hormones of the Ovaries Progesterone Acts with estrogen to bring about the menstrual cycle Helps in the implantation of an embryo in the uterus Helps prepare breasts for lactation 2015 Pearson Education, Inc. Hormones of the Testes Produce several androgens Testosterone is the most important androgen Responsible for adult male secondary sex characteristics Promotes growth and maturation of male reproductive system Required for sperm cell production 2015 Pearson Education, Inc. Table 9.1 Major Endocrine Glands and Some of Their Hormones (1 of 5). 2015 Pearson Education, Inc. Table 9.1 Major Endocrine Glands and Some of Their Hormones (2 of 5). 2015 Pearson Education, Inc. Table 9.1 Major Endocrine Glands and Some of Their Hormones (3 of 5). 2015 Pearson Education, Inc. Table 9.1 Major Endocrine Glands and Some of Their Hormones (4 of 5). 2015 Pearson Education, Inc. Table 9.1 Major Endocrine Glands and Some of Their Hormones (5 of 5). Other Hormone-Producing Tissues and Organs Parts of the small intestine Parts of the stomach Kidneys Heart Many other areas have scattered endocrine cells 2015 Pearson Education, Inc. Placenta Produces hormones that maintain pregnancy Some hormones play a part in the delivery of the baby Produces human chorionic gonadotropin (hCG) in addition to estrogen, progesterone, and other hormones 2015 Pearson Education, Inc. Table 9.2 Hormones Produced by Organs Other Than the Major Endocrine Organs (1 of 3). 2015 Pearson Education, Inc. Table 9.2 Hormones Produced by Organs Other Than the Major Endocrine Organs (2 of 3). 2015 Pearson Education, Inc. Table 9.2 Hormones Produced by Organs Other Than the Major Endocrine Organs (3 of 3). Developmental Aspects of the Endocrine System In the absence of disease, efficiency of the endocrine system remains high until old age Decreasing function of female ovaries at menopause leads to such symptoms as osteoporosis, increased chance of heart disease, and possible mood changes 2015 Pearson Education, Inc. Developmental Aspects of the Endocrine System Efficiency of all endocrine glands gradually decreases with aging, which leads to a generalized increase in incidence of: Diabetes mellitus Immune system depression Lower metabolic rate Cancer rates in some areas 2015 Pearson Education, Inc.