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Endocrine System Anatomy and Physiology What is the Endocrine System? A communication and control system Organs of the endocrine system are called glands Are all glands part of the endocrine system? NO! Exocrine glands are not. These include sweat glands and salivary glands. What is a hormone? A chemical secreted by an endocrine gland Hormones are the main regulators of metabolism, growth and development, reproduction, and many other activities There are two major classes of hormones These are: Steroid hormones Non-steroid hormones The difference is the mechanism by which they influence target organ cells. Regulation of Hormone Secretion • Hormone secretion is controlled by homeostatic feedback • Negative Feedback- mechanisms that reverse the direction of a change in a physiological system • Positive Feedback-(uncommon) mechanisms that amplify physiological changes An example of how negative feedback works Look in your textbook on page 350 for diagram • The intestines absorb glucose after a meal. • Blood glucose level increases. • Pancreas responds to the high glucose level by secreting insulin. • Insulin causes the liver to take up more glucose. • Homeostasis is restored for awhile. • Eventually blood glucose drops because you haven’t eaten in awhile, so you feel hungry, so you eat. So…the cycle begins again. Mechanisms of Endocrine Disease • Hypersecretion-secretion of an excess of hormones • Hyposecretion-insufficient hormone secretion • Target Cell insensitivity produces results similar to hyposecretion Prostaglandins (PGs) • Tissue hormones • Influence respiration, blood pressure, gastrointestinal secretions, inflammation, and the reproductive system • Important in treatment of ulcers, high blood pressure, and asthma • Aspirin and other common treatments create their effects by altering the functions of PGs. Pituitary Gland • Located in the brain’s diencephalon • Though it is the size of a pea, it is really two endocrine glands – the anterior pituitary and the posterior pituitary Anterior Pituitary Gland Hormones • Thyroid-stimulating hormone (TSH) – stimulates thyroid gland • Adrenocorticotropic hormone (ACTH) – stimulates adrenal cortex • Follicle-stimulating hormone (FSH) – stimulates reproductive organs to mature • Luteinizing hormone (LH) – works with FSH. In females, it causes ovulation. In males, it stimulates production of testosterone • Prolactin – during pregnancy, prepares the breasts for lactation • Growth hormone (GH) – see next slide… Anterior Pituitary Gland Hormones • More about Growth Hormone (GH) – – moves amino acids out of the blood and into the cells, accelerating the building of proteins – also affects the fat and carbohydrate metabolism and thus affects blood glucose levels – increases blood glucose where insulin decreases blood glucose – Hypersecretion of GH during the early years of life results in GIGANTISM. – Hypersecretion of GH after normal growth years results in ACROMEGALY. – Hyposecretion of GH during the growth years causes pituitary dwarfism. Posterior Pituitary Gland • Secretes two hormones: – Antidiuretic hormone (ADH) • Decreases urine volume • Hyposecretion of this hormone causes diabetes insipidus, treated by replacement doses of ADH – Oxytocin • Produced during pregnancy – Stimulates contraction of the pregnant uterus when it is time for labor – Causes breasts to release milk A little trivia about the Posterior Pituitary Gland • Doesn’t actually produce these two hormones…do you want to guess which part of the brain does this? • The hypothalamus Thyroid Gland • Located in the neck anterior to trachea • Takes up iodine from the diet • Hormones – Thyroxine – Triiodothyronine – Calcitonin Thyroid Gland Disease • Hyperthyroidismdramatically increases the metabolic rate. Can cause brittle hair, dry skin, unintended weight loss, enlarged thyroid • Graves diseaseHyperthyroidism with exopthalmos Thyroid Imaging • Ultrasound • Nuclear Medicine Thyroid Gland Disease • Hypothyroidism-under secretion of thyroid hormone. • Creatinism-hyposecretion of thyroid hormones in formative years – – – – low metabolic rate retarded growth retarded sex organ development metal retardation Thyroid Gland Disease • Myxedema-late life hyposecretion of thyroid hormones – – – – lessens mental and physical vigor weight gain loss of hair accumulation of mucous fluid in tissue most often around eyes Parathyroid Glands • Four small glands located on the back of the thyroid gland. • Secretes Parathyroid Hormone • Increases the concentration of calcium in the blood-opposite of calcitonin • Stimulates bone-resorbing cells or osteoclasts, to increase their breakdown of bone’s hard matrix thus weakening the bone Adrenal Gland • Sits on top of each kidney • Contains – Adrenal cortex which secretes mineralocorticoids hormones – Adrenal medulla – the inner portion of the adrenal gland, which produces • Epinephrine also called adrenaline • Norepinephrine – They help the body to resist stress and are often called the ‘fight or flight” hormones Mineralocorticoids hormones • Aldosterone– to increase the amount of sodium and decrease the amount of potassium in the blood. – To speed up kidney reabsorption of water • Glucocorticoids – help maintain normal blood glucose concentration – increases gluconeogenesis- a process that converts amino acids or fatty acids to glucose • Androgens – Females stimulate the female sexual drive – Males- they are similar to testosterone and since so much testosterone is secreted adrenal androgens are physiologically insignificant Pancreatic Islets • Also called islets of Langerhans-cells scattered throughout the pancreas • Types of cells in pancreatic islets – Alpha secretes glucagon – Beta secretes insulin • Glucagon and Insulin are antagonist Diabetes Mellitus • A normal blood glucose is 80-120 mg • Pancreatic islets secrete a normal amount of insulin, a normal amount of glucose enters the cells and a normal amount of glucose stays behind in the blood • If too much insulin is secreted hypoglycemia occurs • If too little insulin is secreted DM occurs (also called hyperglycemia) Other Glands • Female sex glands-ovaries • Males-sperm • Thymus-larger in children, produces thymosin which assists in the development and function of the body’s immune system • Placenta-chorionic gonadotropins, estrogen and progesterone • Pineal Gland-melatonin-inhibits the tropic hormones that affect the ovaries