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Endocrine system

Endocrine system. Introduction. Along with nervous system it controls and coordinates activity of body Instead of nerve impulses, it uses hormones Hormones are chemical messengers that are released into blood or lymph 2 Types of Horomones : Steroid=lipid soluble

rinaldo-cahill
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Endocrine system

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  1. Endocrine system

  2. Introduction • Along with nervous system it controls and coordinates activity of body • Instead of nerve impulses, it uses hormones • Hormones are chemical messengers that are released into blood or lymph • 2 Types of Horomones: • Steroid=lipid soluble • Amino Acid based=water soluble

  3. Functions of endocrine system • Reproduction • Growth and development • Mobilization of body defenses • Maintenance of homeostasis • Regulation of metabolism

  4. Extent of Hormone activity is dependent upon… • Blood level of hormones • Number of receptors on target cells • Strength of binding between hormone and receptors

  5. Hormones act on target cells in four ways • Change permeability of plasma membrane • Synthesize proteins (enzymes) in cell • Activate or inactivate enzymes • Stimulate mitosis

  6. Endocrine vs. exocrine • Exocrine • Contains ducts that empty into membranous surfaces • Non-hormone products • Ex: Sweat glands • Endocrine • Ductless glands that empty into blood or lymph • Hormonal products • Ex: Thyroid gland

  7. Control of hormone release • Negative feedback (usually) • Stimulus or low levels of hormones will trigger the release of hormones • Hormone release stops once an appropriate level in blood is reached

  8. Three types of stimuli that activate endocrine organs • Hormonal (most common) • Endocrine system is activated by other hormones • Example: Hypothalamus will stimulate anterior pituitary to secrete hormones->makes other glands secrete hormones • Humoral • Changing levels of blood ions cause release of hormones • PTH will be secreted as Ca2+ in blood decreases • Neural (Rare) • Nerve fibers release hormones • Sympathetic NS stimulation will release epinephrine

  9. Major Endocrine Glands and Organs • Pituitary • Thyroid • Parathyroid • Adrenal • Pancreas • Pineal • Thymus • Gonads • Placenta

  10. Pituitary gland • Size of a grape • Located on inferior side of hypothalamus • Surrounded by Turks saddle • Two parts: • Anterior pituitary- glandular tissue • Posterior pituitary- nervous tissue

  11. Anterior Pituitary • Growth hormone (GH) • Stimulates cells of skeletal muscles and long bones to increase in size. • Increases rate of mitosis • Concentration decreases with age • Secretion is greater at night • Homeostatic imbalance: Hyposecretion can lead to pituitary dwarfism. Hypersecretion can lead to gigantism. If hypersecretion occurs after bone growth has stopped the result is acromegaly, or abnormal bone growth (usually occurs in facial bones) • Adrenocorticotropic hormone (ACTH) • Stimulates production of cortisol (stress hormone) by adrenal glands

  12. Anterior Pituitary • Thyroid stimulating hormone (TSH) • Stimulates thyroid to grow and make thyroid hormones • Follicle stimulating hormone (FSH) • In men it promotes the production of sperm. In women, FSH will stimulate development of a follicle. • Luteinizing hormone (LH) • Triggers ovulation of an egg and then causes ruptured follicle to become a corpus luteum which then produces progesterone and estrogen (promotes pregnancy)

  13. Anterior pituitary • Gonadtropic hormones • Regulates hormonal activity in ovaries and testes • Prolactin • Stimulates breast milk development and milk production during pregnancy. Its function in males is unknown

  14. Posterior pituitary • Doesn’t make hormones • Releases hormones that are made by hypothalamus • Not strictly an endocrine gland • Remember it doesn’t make hormones, it only releases them

  15. Posterior Pituitary • Oxytocin • Stimulates contractions in women and causes milk letdown in nursing mothers • Pitocin-synthetic oxytocin given to mothers to increase labor • Positive feedback- Doesn’t oppose a change • Antidiuretic hormone (ADH) • Will inhibit urine production if solute concentration in blood is too high (retain water) • Urine volume will decrease, blood volume will increase. In large amounts it increases blood pressure by constricting arterioles. Because of this, it is often referred to as a vasopressin. • Alcohol inhibits ADH • Diuretics increase urine production • Homeostatic imbalance: Hyposecretion of ADH will lead to diabetes insipidus(excessive urine)

  16. Thyroid Gland • Located in front of trachea, just below the larynx (Adam’s apple) • Composed of two hormones that contain active iodine • Iodine is very important to help make other hormones

  17. Thyroid gland • Thyroxin/T4 • Secreted by thyroid follicles • T3 • Converted to T4 at the target cell • Homeostatic imbalance- Without iodine (food you eat contains enough iodine) a goiter can develop. A goiter is an enlarged thyroid. TSH will call for T3, the thyroid will expand trying to put T3 out but without iodine the body will only make the non-functional part of T3, this will fail to stop TSH, making the body put out more TSH. • Calcitonin • Decreases blood calcium levels by allowing calcium to be deposited into bones. It’s the antagonist to the PTH.

  18. Homeostatic Imbalances of T3 and T4-Hyperthyroidism and Hypothyroidism Hypothyroidism Hyperthyroidism • Cretinism • Deficiency of TH, causes dwarfism and occurs in infants • Myxedema • Physical and mental sluggishness in adults; results in puffiness of face, fatigue, poor muscle tone, and low body temperature • Graves disease • Rapid heartbeat, weight loss, nervous and agitated behavior and inability to relax

  19. Cretinism • Myxdema • Graves Disease

  20. Parathyroid Gland • Tiny tissues that are found on the posterior surface of the thyroid gland. • Homeostatic imbalance-If blood calcium levels fall too low, neurons will become overactive and cause tetany, or uncontrolled spasms. This is why doctors try to leave part of the thyroid gland if there are problems. • Parathyroid Hormone (PTH) • Increases blood calcium by stimulating osteoclasts to break bone down, releasing calcium into blood. It also stimulates the kidneys and intestines to absorb more calcium.

  21. Adrenal Gland • Two bean shaped glands that curve over the top of each kidney. Outer portion is the cortex and the inner portion is the medulla.

  22. Adrenal Gland- Cortex • Aldosterone • Mineralocorticoid • Helps kidney conserve sodium and excrete potassium, maintains blood pressure. • Promotes reabsorption of sodium which results in water retention. This increases blood volume and, in turn, blood pressure • Cortisone/Cortical • Glucocorticoid • Promotes normal cell metabolism and helps body resist long term stressors by increasing blood glucose levels. It reduces swelling and imflammation by inhibiting immune system • Sex hormones • Produces both sex hormones (male and female) in low levels. Mostly androgens (male) but trace amounts of estrogen (female) • Homeostatic imbalance: • Hyposecretion of all adrenal cortex hormones will result in Addison’s Disease, which causes a bronze color of skin, decreased sodium levels and as a result, water retention as awell as low blood pressure. • Homeostatic imbalance: • Hypersecretion will cause Cushing’s Syndrome, blood glucose will remain high, too much sodium will be retained, skin will become puffy and it has a masculinizing effect in women.

  23. Addison’s Cushing’s Disease Syndrome

  24. Adrenal Gland-Medulla • Epinephrine/Adrenaline and Norepinephrine/Nonadrenaline • Sympathetic Nervous System, increase blood pressure, heart rate, blood glucose levels and dilate passageways of lungs

  25. Pancreas • Located behind stomach, contains specialized calls called islets, or islets of Langerhans, which secrete glucagon and insulin

  26. Pancreas • Insulin • Lowers blood glucose levels. High glucose will cause beta cells of islets to release insulin. Insulin will decrease blood glucose concentrations by causing cells to uptake glucose and allowing liver to store it as glycogen. • Homeostatic imbalance- Diabetes mellitus (means sweet) Blood glucose is too high, spilling into urine because kidneys cannot absorb it fast enough. As glucose leaves, water follows causing dehydration. Type I (juvenile), II (mature onset). Hypoglycemia-low blood sugar • Glucagon • Raises blood glucose levels. Low blood glucose will cause alpha cells of islets to stimulate the liver to break down glycogen to glucose.

  27. Pineal Gland • Found in brain • Melatonin • Maintains Circadian Rhythm (sleep cycles). Levels of melatonin are higher at night.

  28. Thymus • Located in upper thorax, posterior to sternum • Thymosin • Mature t-lymphocytes (a type of white blood cell) that is important to immune function. • Larger in children, shrinks as you age

  29. Gonads • Ovaries • Estrogen • Stimulates development of secondary sex characteristics, stimulates uterine lining during pregnancy • Progesterone • Promotes growth of uterine lining • Testes • Testosterone • Development of adult male sex characteristics, necessary for sperm production

  30. Placenta • Temporarily formed in uterus, produces human chorionic gonadotropin (hCG) • Hormone that over the counter pregnancy tests test for • Stimulates the ovaries to continue to produce estrogen and progresterone so that the lining of the uterus is not sloughed off.

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