Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Neuroendocrine tumor wikipedia , lookup
Hypothyroidism wikipedia , lookup
Hormone replacement therapy (male-to-female) wikipedia , lookup
Bioidentical hormone replacement therapy wikipedia , lookup
Graves' disease wikipedia , lookup
Hyperthyroidism wikipedia , lookup
Hyperandrogenism wikipedia , lookup
Growth hormone therapy wikipedia , lookup
Pituitary apoplexy wikipedia , lookup
Lecture Outline The Endocrine System Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Endocrine Glands o o Endocrine glands are ductless Secrete hormones • Chemical signals that influence: • Metabolism Growth and development Homeostasis Categories of hormones Peptides (proteins, glycoproteins, and modified amino acids) – most hormones Steroid hormones Endocrine Glands o How Hormones Function • Second messenger system Peptide hormone binds to a receptor protein on the plasma membrane Peptide hormone (“first messenger”) activates a “second messenger” (cyclic AMP and calcium) Second messenger sets in motion an enzyme cascade that leads to a cellular response Change in cellular behavior Formation of an end product that leaves the cell Endocrine Glands • Intracellular mechanism of hormone function Steroid hormones (lipids) diffuse across the plasma membrane Once inside the cell, steroid hormones bind to receptor proteins Hormone-receptor complex binds to DNA, activating particular genes Gene activation leads to production of cellular enzymes that cause cellular changes Endocrine Glands o Hormone Control • Many hormones affect concentrations of certain substances in the blood Other hormones are involved in normal function of various organs Release of hormones controlled by one or more of the following: • • The nervous system The action of other hormones Negative feedback mechanisms Hypothalamus and Pituitary Gland o Hypothalamus • Controls secretions of the pituitary gland Neurosecretory cells produce • Antidiuretic hormone (ADH) Oxytocin Hypothalamus and Pituitary Gland o Posterior pituitary • Stores hypothalamic hormones ADH and oxytocin ADH • Released when neurons in the hypothalamus detect that the blood is too concentrated with salt Causes more water to be reabsorbed into kidney capillaries Raises blood pressure by vasoconstriction of blood vessels Diabetes insipidus results from the inability to produce ADH Hypothalamus and Pituitary Gland • Oxytocin Causes uterine contraction during childbirth Causes milk letdown when a baby is nursing Release of oxytocin is controlled by positive feedback Hypothalamus and Pituitary Gland o Anterior pituitary • • Controlled by hypothalamic hormones Hormones that affect other glands • Thyroid-stimulating hormone (TSH) Adrenocorticotropic hormone (ACTH) Gonadotropic hormones Effects of other hormones Prolactin (PRL) Growth hormone (GH) Hypothalamus and Pituitary Gland • Effects of growth hormone Affects the height of an individual Pituitary dwarfism results if too little GH is produced during childhood If too much GH is produced during childhood, a person can become a giant Acromegaly results when too much GH is secreted in adulthood Thyroid and Parathyroid o Thyroid Gland • Two forms of thyroid hormone • Triiodothyronine (T3) contains 3 iodine atoms Thyroxine (T4) contains 4 iodine atoms Effects of thyroid hormone Increase the metabolic rate Stimulate all cells of the body Thyroid and Parathyroid • Simple goiter Caused by a lack of iodine Thyroid enlarges in response to constant stimulation by the anterior pituitary Thyroid and Parathyroid • Congenital hypothyroidism Thyroid fails to develop properly Undersecretion of thyroid hormone Individuals are short and stocky • Myxedema Hypothyroidism in adults Characterized by Lethargy Weight gain Loss of hair Slower pulse rate Lowered body temperature Thick and puffy skin Thyroid and Parathyroid • Hyperthyroidism (Grave’s Disease) Oversecretion of thyroid hormone Exophthalmic goiter forms Edema in eye socket tissues Swelling of the muscles that move the eyes Symptoms include Hyperactivity Nervousness and irritability Insomnia Thyroid and Parathyroid • Calcitonin Helps control blood calcium levels Secreted when the blood calcium levels rise Brings about the deposit of calcium in the bones Thyroid and Parathyroid o Parathyroid Glands • • Posterior surface of the thyroid gland Produces parathyroid hormone (PTH) Causes blood phosphate (HPO42-) level to decrease Causes blood calcium (Ca2+) level to increase Promotes the release of calcium from the bones Promotes the reabsorption of calcium by the kidneys Activates vitamin D in the kidneys, which stimulates the reabsorption of calcium from the intestines Hypocalcemic tetany results when there is insufficient secretion of PTH Adrenal Glands o Adrenal Medulla • • • • • Inner portion Under nervous control Secretes epinephrine (adrenaline) and norepinephrine (noradrenaline) Causes “fight or flight” responses Provide a short-term response to stress Adrenal Glands o Adrenal Cortex • Outer portion – 3 layers, each produces a different set of hormones Under the control of ACTH Hormones • • Provide a long-term response to stress Mineralcorticoids Glucocorticoids Male and female sex hormones Adrenal Glands • Glucocorticoids (cortisol) Raises the blood glucose level in at least 2 ways: Counteracts the inflammatory response and can relieve swelling and pain Can also make a person susceptible to injury and infection Adrenal Glands • Mineralcorticoids (aldosterone) Targets the kidney Promotes renal absorption of sodium and water Promotes renal excretion of potassium ACTH is not the primary controller for aldosterone secretion Renin-Angiotensin mechanism stimulates aldosterone secretion when the blood sodium level and blood pressure are low Renin-Angiotensin-Aldosterone system raises blood pressure in two ways: Angiotensin II constricts arterioles Aldosterone causes the kidneys to reabsorb sodium Atrial natriuretic hormone (ANH) is antagonistic to aldosterone Adrenal Glands • Malfunction of the Adrenal Cortex Addison Disease Hyposecretion of adrenal cortex hormones Excessive (but ineffective) ACTH causes bronzing of the skin Because glucose cannot be replenished without cortisol, individuals are susceptible to infection Lack of aldosterone results in the development of low blood pressure and possibly severe dehydration Cushing Syndrome Hypersecretion of adrenal cortex hormones Tendency towards diabetes mellitus Excess aldosterone leads to hypertension Pancreas o Composed of two types of tissue • • Exocrine – secretes digestive juices Endocrine tissue (pancreatic islets or islets of Langerhans) produces: Insulin Secreted when blood glucose level is high Stimulates the uptake of glucose by most body cells Glucagon Secreted when blood glucose levels are low Targets liver and adipose tissue Stimulates liver to break down glycogen to glucose Pancreas o Diabetes Mellitus • Insulin-sensitive body cells are unable to take up and/or metabolize glucose Blood glucose level is elevated (hyperglycemia) Symptoms: • • Polyphagia – extreme hunger Glycosuria – glucose in the urine Polyuria – excessive water loss through urine Polydipsia – extreme thirst Pancreas • Two forms of diabetes mellitus Type I – insulin-dependent diabetes mellitus Pancreas does not produce insulin Immune cells destroy the pancreatic islets Type II – non-insulin-dependent diabetes mellitus Normal or elevated amounts of insulin are present in the blood Receptors on the cells do not respond to insulin Other Endocrine Glands o Testes and ovaries • • • Testes produce androgens (testosterone) Ovaries produce estrogens and progesterone Secretion is controlled by the hypothalamus and the pituitary Other Endocrine Glands • Androgens Increased testosterone secretion during puberty stimulates the growth of the penis and the testes Brings about and maintains the male secondary sex characteristics Facial, axillary, and pubic hair Enlargement of larynx and the vocal cords Muscular strength Stimulates oil and sweat glands of the skin Other Endocrine Glands • Estrogen and Progesterone Required for breast development Regulation of the uterine cycle Estrogens Stimulate the growth of the uterus and the vagina during puberty Necessary for egg maturation Responsible for secondary sex characteristics Female body hair Fat distribution Other Endocrine Glands o Thymus Gland • • • o Most active during childhood Transforms lymphocytes into thymusderived lymphocytes (T-lymphocytes) Epithelial cells secrete hormones called thymosins Pineal Gland • • • Located in the brain Produces the hormone melatonin Melatonin is involved in daily sleepwake cycle Other Endocrine Glands o Hormones from Other Tissues • Leptin • Produced by adipose tissue Signals satiety in hypothalamus Growth Factors – stimulate cell division and mitosis Granulocyte and macrophage colonystimulating factor Platelet-derived growth factor Epidermal growth factor and nerve growth factor Tumor angiogenesis factor Other Endocrine Glands • Prostaglandins Potent chemical signals Act locally Some effects of prostaglandins include: Uterine contractions Mediate the effects of pyrogens Reduce gastric secretion Lower blood pressure Inhibit platelet aggregation The Importance of Chemical Signals o Cells and organs communicate with one another using chemical signals Chemical signals between individuals o • • Called pheromones Humans produce airborne chemicals from a variety of areas Effects of Aging o Thyroid disorders • • o Hypothyroidism Hyperthyroidism Diabetes Homeostasis o The endocrine system and the nervous system work together to maintain homeostasis The endocrine system helps regulate the following: o • • • • • Digestion Fuel metabolism Blood pressure and volume Calcium balance Response to the external environment