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Transcript
The Endocrine System Lesson Objectives • • • • By the end of this lesson you should know: The difference between endocrine and exocrine glands Define a hormone The role of the principle endocrine glands 2 examples of hormone supplements Exocrine and endocrine glands Exocrine glands Endocrine glands Definition Have ducts or tubes Have no ducts or tubes Examples Sweat, tear, salivary glands, the liver Pituitary, thyroid, parathyroids, adrenels, pancreas, ovaries or testes Hormones • • • • “A hormone is a chemical messenger produced by an endocrine gland and transported in the bloodstream to act in another part of the body where it has a specific effect” Many hormones are proteins Some are steroid or lipid based such as those of the reproductive system Hormones are involved in co-ordinating the body They interact with the nervous system in achieving this function Comparison of endocrine and nervous systems Feature Endocrine system Speed of action Slow acting Nervous system Fast acting Length of action Type of message Speed of message Areas affected Action lasts a long time Chemical Action lasts a short time Electrical Slow delivery Fast deliver Affects many areas Affects one area The Endocrine System The principal endocrine glands Gland Hormone Function Pituitary Human growth hormone (HGH) Elongates bones in the skeleton Thyroid Thyroxin Controls metabolism Parathyroid Parathormone Releases calcium from bones Pancreas Insulin Causes glucose to be removed from the blood Adrenal adrenalin Allows us to respond to stress Ovaries or testes We will examine this when studying human reproduction Pituitary gland • Peanut sized gland in the middle of the head and is controlled by the hypothalamus • Produces many hormones, e.g. GH, ADH, TSH, LH, FSH Hypothalamus • Links nervous and endocrine systems • Secretes hormones that control the pituitary gland in response to messages from the brain and other hormones • Releasing hormones & inhibiting hormones • e.g. GHRF Pineal gland • Tiny gland located within the brain • Produces a number of hormones, best known one is melatonin • Its function is not fully understood but it seems to play a role in biological rhythms e.g sleep Thyroid • Makes the hormone thyroxin • Iodine which is found in seafood and sea salt is needed to make thyroxine • Thyroxine controls metabolism i.e. rate of chemical reactions in the body Hormone Deficiency and Excess Deficiency of Thyroxine Symptoms • Young children results in reduced physical mental and physical development – cretinism • In adults results in reduced metabolic rate, tiredness, reduced mental and physical activity, the build up of fluid under the skin and weight gain (Myxoedema)– in addition the thyroid glands swell – a condition called goitre Treatment • Involves taking tablets of thyroxine or iodine Excess of Thyroxine Symptoms • Causes an increased metabolic rate, which in turn causes hunger, loss of weight, heat production, sweating, bulging eyes and anxiety (Graves disease) Treatment • May involve removing a part of the thyroid or killing part of it using radioactive iodine Parathyroids • 4 Parathyroids are located in the thyroid gland in the neck • Produce parathormone which controls the release of calcium from bone • Problems with this hormone can result in brittle bones Thymus • The 2 lobes of the thymus gland are located behind the breastbone in the upper chest • Produces a hormone called thymosin which causes lymphocytes to mature and become active • The thymus begins to degenerate around puberty Adrenals • Located on top of the kidneys in the lower back • Produce the hormone adrenalin Pancreas Enzymes Into pancreatic duct Exocrine gland Insulin Into bloodstream Endocrine gland Pancreas • Islets of Langerhans cells • Insulin • Glycogen • Diabetes • Most of the cells in the pancreas produce enzymes (such as amylase and lipase) Hormone supplements Insulin • The inability to produce insulin (or the inability of cells to absorb insulin) results in diabetes Anabolic steroids • Anabolic steroids copy the action of the male hormone testosterone – in particular they build up muscle mass in the body, reduce fat, speed up the repair of injuries and form stronger bones What have you learned? • • • • Do you know… The difference between endocrine and exocrine glands? Can you define a hormone? The role of the principle endocrine glands? 2 examples of hormone supplements? Lesson Objectives – Higher Level By the end of this lesson you should understand: • The control of thyroxine levels through a negative feedback mechanism Control of thyroxine level Goitre • Caused by an underproduction of thyroxine (lack of Iodine in the diet) • Causes pituitary to produce TSH • Low concentration of thyroxine in blood causes the pituitary to produce TSH • TSH combines with iodine to produce thyroxine • If there is a shortage of iodine this can’t happen • Cured by taking iodine tablets What have you learned? Do you understand…. • The control of thyroxine levels through a negative feedback mechanism?