Endocrine System: Hormones and Glands PDF

Introduction (1 of 2) The endocrine system consists of several endocrine glands plus many hormone-secreting cells in organs that have functions besides secreting hormones. In contrast to the nervous system, which controls body activities through the release of neurotransmitters at synapse...

Introduction (1 of 2) The endocrine system consists of several endocrine glands plus many hormone-secreting cells in organs that have functions besides secreting hormones. In contrast to the nervous system, which controls body activities through the release of neurotransmitters at synapses, the endocrine system (cells of endocrine glands) releases hormones into interstitial fluid (fluid that surrounds cells) and then into the bloodstream. Exocrine glands secrete their products into ducts that carry the secretions into a body cavity, into the lumen of an organ, or onto the outer surface of the body. q Sweat glands are one example of exocrine glands. Copyright ©2018 John Wiley & Sons, Inc. 6 Introduction (2 of 2) The endocrine glands include the pituitary, thyroid, parathyroid, adrenal, and pineal glands. Functions of Hormones: 1. Help regulate – Chemical composition and volume of internal environment; metabolism and energy balance; contraction of smooth and cardiac muscle fibers; glandular secretions; immune activities. 2. Control growth and development. 3. Regulate operation of reproductive systems. 4. Help establish circadian rhythms. Copyright ©2018 John Wiley & Sons, Inc. 7 Location of Endocrine Glands and Organs that Contain Endocrine Cells Copyright ©2018 John Wiley & Sons, Inc. 8 Comparison of Control by the Nervous and Endocrine Systems Table 13.1 Comparison of Control by the Nervous and Endocrine Systems Characteristic Nervous System Endocrine System Mediator molecules Neurotransmitters released locally in Hormones delivered to tissues response to nerve impulses throughout body by blood Site of mediator action Close to site of release, at synapse; binds Far from site of release to receptors in postsynaptic membrane (usually); binds to receptors on or in target cells Types of target cells Muscle (smooth, cardiac, and skeletal) Cells throughout body cells, gland cells, other neurons Time to onset of action Typically within milliseconds Seconds to hours or days (thousandths of a second) Duration of action Generally briefer (milliseconds) Generally longer (seconds to days) Copyright ©2018 John Wiley & Sons, Inc. 9 Hormone Action Hormones affect only specific target cells that have the specific protein receptors to bind to a given hormone. Chemically, hormones are either: q lipid-soluble (steroids, thyroid hormones, and nitric oxide) or q water-soluble (modified amino acids, peptides, and proteins). Lipid-soluble hormones affect cell function by altering gene expression. Water-soluble hormones alter cell function by activating plasma membrane receptors, which elicit production of a second messenger that activates various proteins inside the cell. Hormone secretion is controlled by signals from the nervous system, blood chemistry, and other hormones. Copyright ©2018 John Wiley & Sons, Inc. 10 Mechanism of Action of Lipid-Soluble Hormones Copyright ©2018 John Wiley & Sons, Inc. 11 Mechanism of Action of Water- Soluble Hormones Copyright ©2018 John Wiley & Sons, Inc. 12 Hypothalamus and Pituitary Gland (1 of 3) The pituitary gland was considered the “master” gland. The pituitary gland, we now know has itself a master, the hypothalamus (which it is attached to). The pituitary consists of two lobes: the anterior pituitary and the posterior pituitary. q Hormones of the pituitary gland are controlled by inhibiting and releasing hormones produced by the hypothalamus. The anterior pituitary consists of cells that produce: q Human growth hormone (hGH) – stimulates body growth through insulinlike growth factors (IGFs). q Prolactin (PRL) – initiates and maintains milk production by the mammary glands. Copyright ©2018 John Wiley & Sons, Inc. 13 Hypothalamus and Pituitary Gland (2 of 3) Thyroid-stimulating hormone (T S H) – regulates thyroid gland activities. Follicle-stimulating hormone (F S H) and Luteinizing hormone (L H) – regulate activities of the gonads (ovaries and testes). Adrenocorticotropic hormone (A C T H) – regulates activities of the adrenal cortex. Melanocyte-stimulating hormone (M S H) – excessive amount of M S H causes darkening of the skin. Copyright ©2018 John Wiley & Sons, Inc. 14 Hypothalamus and Pituitary Gland (3 of 3) The posterior pituitary contains axon terminals of neurosecretory cells whose cell bodies are in the hypothalamus. Hormones made in the hypothalamus and released in the posterior pituitary include: Oxytocin, which stimulates contraction of the uterus and ejection of milk from the breasts, and Antidiuretic hormone (ADH), which stimulates water reabsorption by the kidneys and constriction of arterioles. Oxytocin secretion is stimulated by uterine stretching and by suckling during nursing. ADH secretion is controlled by the osmotic pressure of the blood and blood volume. Copyright ©2018 John Wiley & Sons, Inc. 15 The Pituitary Gland and Its Blood Supply (1 of 2) Copyright ©2018 John Wiley & Sons, Inc. 16 The Pituitary Gland and Its Blood Supply (2 of 2) Copyright ©2018 John Wiley & Sons, Inc. 17 Hypothalamic Neurosecretory Cells Synthesize Oxytocin and Antidiuretic Copyright ©2018 John Wiley & Sons, Inc. 18 Regulation of Secretion and Actions of Antidiuretic Hormone (ADH) (1 of 2) Copyright ©2018 John Wiley & Sons, Inc. 19 Regulation of Secretion and Actions of Oxytocin (2 of 2) Copyright ©2018 John Wiley & Sons, Inc. 20 Summary of Pituitary Gland Hormones and Their Actions (1 of 2) Table 13.2 Summary of Pituitary Gland Hormones and Their Actions Anterior Pituitary Hormones Hormone Actions Growth hormone (GH) Stimulates liver, muscle, cartilage, bone, and other tissues to synthesize and secrete insulinlike growth factors (IGFs); IGFs promote growth of body cells, protein synthesis, tissue repair, breakdown of triglycerides, and elevation of blood glucose level Thyroid-stimulating Stimulates synthesis and secretion of thyroid hormones by the hormone (TSH) thyroid gland Follicle-stimulating In females, initiates development of oocytes and induces secretion of hormone (FSH) estrogens by the ovaries; in males, stimulates testes to produce sperm Luteinizing hormone (LH) In females, stimulates secretion of estrogens and progesterone, ovulation, and formation of corpus luteum; in males, stimulates testes to produce testosterone Copyright ©2018 John Wiley & Sons, Inc. 21 Summary of Pituitary Gland Hormones and Their Actions (2 of 2) Hormone Actions Prolactin (PRL) In females, stimulates milk production by the mammary glands Adrenocorticotropic Stimulates secretion of glucocorticoids (mainly cortisol) by the adrenal cortex hormone (ACTH), also known as corticotropin Melanocyte-stimulating Exact role in humans is unknown but may influence brain activity; when hormone (MSH) present in excess, can cause darkening of skin Posterior Pituitary Hormones Hormone Actions Oxytocin Stimulates contraction of smooth muscle cells of uterus during childbirth; stimulates milk ejection from mammary glands Antidiuretic hormone (ADH), Conserves body water by decreasing urine output; decreases water loss also known as vasopressin through sweating; raises blood pressure by constricting (narrowing) arterioles Copyright ©2018 John Wiley & Sons, Inc. 22 Thyroid Gland The thyroid gland is butterfly-shaped and is located just below the larynx (voice box). It is composed of right and left lobes, one on either side of the trachea which secrete the: thyroid hormones thyroxine (T4) and triiodothyronine (T3), and parafollicular cells, which secrete calcitonin. Thyroid hormones regulate oxygen use and metabolic rate, cellular metabolism, and growth and development. Secretion is controlled by: q TRH from the hypothalamus and q thyroid-stimulating hormone from the anterior pituitary. Calcitonin (CT) can lower the blood level of calcium; its secretion is controlled by the level of calcium in the blood. Copyright ©2018 John Wiley & Sons, Inc. 23 Location and Histology of the Thyroid Gland Copyright ©2018 John Wiley & Sons, Inc. 24  tired Regulation of Secretion of Thyroid Hormones THS has influence ] on follicular cells T3 and T4 are lipid soluble hormones metabolism take place in cells Copyright ©2018 John Wiley & Sons, Inc. 25 Parathyroid Glands increase calsium concentration The parathyroid glands are embedded on the posterior surfaces of the thyroid. Parathyroid hormone (PTH) regulates the homeostasis of calcium, magnesium, and phosphate by increasing blood calcium and magnesium levels and decreasing blood phosphate level. PTH secretion is controlled by the level of calcium in the blood. Copyright ©2018 John Wiley & Sons, Inc. 26 Location of the Parathyroid Glands photosynthesis Copyright ©2018 John Wiley & Sons, Inc. 27  Parathyroid increase in blood calsium Glands and Homeostasis parafollicular cells in thyroid glands decrease calsuim of Blood levels calsiotomum Calcium how calsium decrease? hormone- calsitonin Levels (1 of 2) parathyroid gland increase calsium cells that break down bone (bones) build bone up/ secrete ground substance- osteoblasts Copyright ©2018 John Wiley & Sons, Inc. 28 Parathyroid Glands and Homeostasis of Blood Calcium Levels (2 of 2) Copyright ©2018 John Wiley & Sons, Inc. 29 Pancreatic Islets The pancreas is a flattened organ located in the curve of the duodenum. q It has both endocrine and exocrine functions. The endocrine portion consists of pancreatic islets or islets of Langerhans, which are made up of alpha and beta cells. q Alpha cells secrete glucagon, and -increasde bgl q beta cells secrete insulin. -decrease bgl Glucagon increases blood glucose level, and insulin decreases blood glucose level. Secretion of both hormones is controlled by the level of glucose in the blood. Copyright ©2018 John Wiley & Sons, Inc. 30 Location and Histology of the Pancreas exocrine - ducks endocrine- blood vessels Copyright ©2018 John Wiley & Sons, Inc. 31 Regulation of glucagon from alfa cells and it effects your liver blood glucose levels Blood Glucose Level by Negative Feedback Systems Involving Glucagon and Insulin (1 of 2) glycogen stored in liver break down in smaller parts Copyright ©2018 John Wiley & Sons, Inc. 32 Regulation of Blood Glucose Level by Negative Feedback Systems Involving Glucagon and Insulin (2 of 2) glucose out of cells Copyright ©2018 John Wiley & Sons, Inc. 33 Adrenal Glands (1 of 2) There are two adrenal glands, one lying atop each kidney. q They consist of an outer adrenal cortex and inner adrenal medulla. adrenial madalla- inner region outer region The adrenal cortex is divided into three zones: q The outer zone secretes mineralocorticoids, q the middle zone secretes glucocorticoids, and q the inner zone secretes androgens. sex hormones Mineralocorticoids (mainly aldosterone) increase sodium and water reabsorption and decrease potassium reabsorption. q Secretion is controlled by the renin–angiotensin–aldosterone pathway. Copyright ©2018 John Wiley & Sons, Inc. 34 Adrenal Glands (2 of 2) Glucocorticoids (the most abundant is cortisol) have the following actions: q protein and triglyceride breakdown, glucose formation, anti- inflammatory effects, and depression of immune responses. q Secretion is controlled by ACTH. Androgens secreted by the adrenal cortex stimulate growth of axillary and pubic hair, aid the prepubertal growth spurt, and contribute to libido. The adrenal medulla consist of cells of the ANS. q It secretes epinephrine and norepinephrine (NE), which are released under stress. Copyright ©2018 John Wiley & Sons, Inc. 35 Location and Histology of the Adrenal Glands (1 of 2) Copyright ©2018 John Wiley & Sons, Inc. 36 Location and Histology of the Adrenal Glands (2 of 2) Copyright ©2018 John Wiley & Sons, Inc. 37 The Renin- Angiotensin- Aldosterone Pathway Copyright ©2018 John Wiley & Sons, Inc. 38 Ovaries and Testes (1 of 2) Gonads are the organs that produce gametes – sperm in males and oocytes in females. The females gonads, the ovaries, are paired oval bodies located in the pelvic cavity and produce: q estrogens, progesterone and inhibin. These female sex hormones regulate: q The menstrual cycle, q Maintain pregnancy, and q Prepare the mammary glands for lactation. q They also help establish and maintain the feminine body shape. Copyright ©2018 John Wiley & Sons, Inc. 39 Ovaries and Testes (2 of 2) The male gonads, the testes, are oval glands that lie inside the scrotum and produce: q testosterone and inhibin. Testosterone: q Regulates production of sperm and q Stimulates the development and maintenance of masculine characteristics such as beard growth and deepening of the voice. Copyright ©2018 John Wiley & Sons, Inc. 40 Pineal Gland The pineal gland is a small endocrine gland attached to the roof of the third ventricle of the brain at the midline. One hormone secreted by the pineal gland is melatonin, which contributes to setting the body’s biological clock. More melatonin is released in darkness and during sleep; less melatonin is liberated in strong sunlight. Melatonin levels are higher in children and decline with age into adulthood. Copyright ©2018 John Wiley & Sons, Inc. 41 Other Hormones Cells in organs other than those usually classified as endocrine glands have an endocrine function and secrete hormones. These organs and tissues include: q the thymus, gastrointestinal tract, kidney, heart, adipose tissue, and placenta. Prostaglandins and leukotrienes act locally in most body tissues. Copyright ©2018 John Wiley & Sons, Inc. 42  Summary of Other Hormones (1 of 4) Table 13.3 Summary of Hormones Produced by Other Organs and Tissues That Contain Endocrine Cells Thymus Source and Hormone Actions Thymosin Promotes the maturation of T cells (a type of white blood cell that destroys microbes and foreign substances) and may retard the aging process (discussed in Chapter 17) Gastrointestinal Tract Source and Hormone Actions Gastrin Promotes secretion of gastric juice and increases movements of the stomach (discussed in Chapter 19) Glucose-dependent Stimulates release of insulin by pancreatic beta cells (discussed in Chapter 19) insulinotropic peptide (GIP) Secretin Stimulates secretion of pancreatic juice and bile (discussed in Chapter 19) Copyright ©2018 John Wiley & Sons, Inc. 43 Summary of Other Hormones (2 of 4) Source and Hormone Actions Cholecystokinin (CCK) Stimulates secretion of pancreatic juice, regulates release of bile from the gallbladder, and brings about a feeling of fullness after eating (discussed in Chapter 19) Copyright ©2018 John Wiley & Sons, Inc. 44 Summary of Other Hormones (3 of 4) Kidney Source and Hormone Actions Erythropoietin (EPO) Increases rate of red blood cell production (discussed in Chapter 14) Heart Source and Hormone Actions Atrial natriuretic peptide (ANP) Decreases blood pressure (discussed in Chapter 16) Copyright ©2018 John Wiley & Sons, Inc. 45 Summary of Other Hormones (4 of 4) Adipose Tissue Source and Hormone Actions Leptin Suppresses appetite and may increase the activity of FSH and LH (discussed in Chapter 20) Placenta Source and Hormone Actions Human chorionic gonadotropin (hCG) Stimulates the ovary to continue production of estrogens and progesterone during pregnancy (discussed in Chapter 24) Copyright ©2018 John Wiley & Sons, Inc. 46 The Stress Response (1 of 3) Any stimulus that produces a stress response is called a stressor. A stressor may be almost any disturbance: q heat or cold, environmental poisons, toxins given off by bacteria, heavy bleeding from a wound or surgery, or a strong emotional reaction. Stressors may be pleasant or unpleasant, and they vary among people and even within the same person at different times. If stress is extreme, unusual, or long lasting, it triggers the stress response, which occurs in three stages: 1. An initial fight-or-flight response 2. A slower resistance reaction 3. And eventually exhaustion Copyright ©2018 John Wiley & Sons, Inc. 47 The Stress Response (2 of 3) The fight-or-flight response, initiated by nerve impulses from the hypothalamus to the sympathetic division of the autonomic nervous system, including the adrenal medullae, quickly mobilizes the bodyʼs resources for immediate physical activity. It brings huge amounts of glucose and oxygen to the organs that are most active in warding off danger: q the brain, which must become highly alert; q the skeletal muscles, which may have to fight off an attacker or flee; and q the heart, which must work vigorously to pump enough blood to the brain and muscles. Copyright ©2018 John Wiley & Sons, Inc. 48 The Stress Response (3 of 3) The resistance reaction (the second stage) helps the body continue fighting a stressor long after the fight-or-flight response dissipates. Generally, the resistance stage is successful in seeing us through a stressful episode, and our bodies then return to normal. Occasionally, however, the resistance stage fails to combat the stressor. Exhaustion results from depletion of body resources during the resistance stage. Prolonged exposure to high levels of cortisol and other hormones involved in the resistance reaction causes wasting of muscles, suppression of the immune system. Copyright ©2018 John Wiley & Sons, Inc. 49 Aging and the Endocrine System Although some endocrine glands shrink as we get older, their performance may or may not be compromised. Production of human growth hormone, thyroid hormones, cortisol, aldosterone, and estrogens decrease with advancing age. With aging, the blood levels of PTH, TSH, LH, FSH rise. The pancreas releases insulin more slowly with age, and receptor sensitivity to glucose declines. After puberty, thymus size begins to decrease, and thymic tissue is replaced by adipose and areolar connective tissue. Copyright ©2018 John Wiley & Sons, Inc. 50 Photographs of People with various Endocrine Disorders Copyright ©2018 John Wiley & Sons, Inc. 51