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The Endocrine System By Evil Mr. Bleecker Endocrine vs Nervous System NERVOUS • Uses impulses sent along axons and chemical neurotransmitters at synapses ENDOCRINE • Uses chemical hormones released from glands into the blood • Receptors are on postsynaptic membrane • Receptors are on the plasma membranes of target cells or intercellular • Signals are very fast (milliseconds) • Signals are slower (seconds to days) • Response is immediate but short-lived • Response is delayed but more sustained Characteristics of Hormones Hormones: exert their effects some distance from where they are produced are active under very low (nanogram 10-9) concentrations in the blood usually have a short half-life in the body several seconds to 60 mins. They are degraded by enzymes in their target cells or in the kidney or liver. Characteristics of Hormones Hormones bring about their effects by altering cell activity. The precise response depends on the target cell type. Typical cellular effects include: Altering membrane permeability Stimulating protein synthesis Activating enzymes Inducing cells to secrete materials Stimulating mitosis Control of Hormone Release Synthesis and release of most hormones are regulated by a Negative Feedback System. As hormone levels rise, they cause target organ effects which inhibit further hormone release. Hormone - Target Cell Specificity Hormones circulate to virtually all tissues but influence the activity of only certain tissue cells, known as its target cells. The Hypothalamus Contros the Anterior Pituitary Hypothalamus “tastes blood” for hormone levels. It sends orders to the anterior/posterior pituitary to regulate the release of hormones. Hormonal control rather than by nerves Hypothalamus neurons synthesize releasing and inhibiting hormones. Hormones secreted regulate the secretions of the anterior pituitary HORMONE GLAND NORMAL EFFECTS OF HORMONE CONTROL OF RELEASE TARGET ORGAN EFFECTS OF HYPER- AND HYPOSECRETION pituitary gland Pituitary gland is located in the diencephalon below the hypothalamus Structurally and functionally divided into: Anterior lobe Posterior lobe Anterior Pituitary – Master Gland growth hormone - GH prolactin- PRL adrenocorticotropic hormone - ACTH thyroid stimulating hormone - TSH lutenizing hormone - LH follicle-stimulating hormone - FSH posterior pituitary antidiuretic hormone – ADH oxytocin - OT pituitary gland growth hormone Direct effects are the result of GH binding its receptor on target cells. Target cells then believe they should take in more nutrients and grow, then divide GROWTH HORMONE DISORDERS 12 year-old with mother Gigantism (Acromegaly) refers to a condition characterized by extreme physical size and stature due to a hyper-secretion of growth hormone during infancy, childhood or adolescence Remember Andre the Giant? (WWF) At the Start of his Career By the End of his Career Topping out at 625 lbs! Click for the action------> GROWTH HORMONE DISORDER #2 Dwarfed brothers with researcher in India Dwarfism results from a GH deficiency in childhood, leading to a maximum height of 4 feet typically with normal body proportions. If diagnosed before puberty, hormone replacement therapy can promote nearly normal growth. THE THYROID GLAND Thyroid gland is a large gland located in the neck, just below the larynx. Needs IODINE to work properly. Thyroid follicle cells stimulated by the anterior pituitary gland hormone TSH = Thyroid-stimulating Hormone Secretes THRYOXIN = adjusts metabolism for all body cells – ie. Burning more glucose Goiter - Due to iodine deficiency Hypothyroid in Infants Cretinism: Hypothyroid from end of 1st trimester to 6 months after birth. Severe mental retardation Short disproportionately sized body with a thick neck and tongue Hypothyroid in Adults In adults, it is called Myxedema: Accumulation of proteins and fluid in subcutaneous tissue. Symptoms: Decreased metabolic rate. Weight gain. Decreased ability to adapt to cold. Lethargy (= fatigue) Hyperthyroid in Adults Grave’s disease Elevated metabolic rate (rapid heartbeat, sweating, nervousness) and bulging eyeballs (expophthalmia) HORMONES OF CALCIUM BALANCE Calcitonin - protein Produced by thyroid Reduces blood serum calcium levels by stimulating calcium uptake in bone Important only in childhood when bones are quickly growing Parathyroid Glands – Calcium II Parathyroid Hormone (PTH) Produced by parathyroid glands Opposite effect to Calcitonin Increases blood calcium levels by enhancing absorption of calcium in the small intestine, bone and promoting Ca2+ reabsorption in the kidney Adrenal Gland Paired organs that cap the kidneys. Each gland consists of an outer cortex and inner medulla. Adrenal Cortex Adrenal cortex Stimulated hormonally (ACTH = Adrenal CorticoTropic Hormone) Secretes corticosteroids 1. Glucocorticoids – raises blood glucose, increases protein breakdown. Another is cortisone = anti-inflammatory 2. 3. Aldosterone (Mineralcorticosteroid) – sodium reabsorption in kidneys Sex Hormones – stimulates sex organs, development of reproductive organs Negative Feedback Loop Low blood sodium sensed by kidneys enzyme Angiotensin secreted which turns on secretion of aldosterone by kidney Increased H20 absorbed to raise pressure GLUCOCORTICOIDS At high concentrations, cortisol has pronounced antiinflammatory and anti-immune effects including: Depressing cartilage and bone formation Inhibiting inflammation GLUCOCORTICOIDS in Excess Cushing’s disease = glucorticoid excess Symptoms include hyperglycemia (high blood sugar), loss of muscle and bone protein, moon face, and a redistribution of fat to the abdomen and posterior neck (causing a “buffalo hump”) Excess of aldosterone causes excessive Na reabsorption, flooding tissues with water = edema GLUCOCORTICOIDS – Insufficiencies JFK had Addison’s, which he kept from public knowledge Addison’s disease is the major hypo-secretory disorder of the adrenal cortex, usually involving of both glucocorticoids and mineralcorticoids. Victims lose weight, demonstrate hypoglycemia and reduced levels of sodium, and show an increase in skin pigmentation (bronzing) Adrenal Medulla Synthesizes and secretes Epinepherine and some NorEpinepherine Sympathetic Nervous System hormones made here!!! Fight or Flight!!! ANTIDIURETIC HORMONE Antidiuretic Hormone (ADH; vasopressin) The main regulator of body’s water (osmotic)balance ADH increases the reabsorption rate of water in kidney Secretion is regulated in the hypothalamus by osmoreceptors, which sense water concentration Pancreas Islets of Langerhans secrete insulin into the bloodstream Insulin tells cells to absorb sugar and store it Huge storage in liver as GLYCOGEN and in muscles!!! Homeostatis & Regulating Blood Sugar Levels Negative feedback loops If blood sugar rises, insulin is secreted to bring it down If blood sugar lowers, glucagon is secreted to place sugar into the blood INSULIN Diabetes mellitus results from hypo-secretion of insulin or hypo-activity of insulin. When insulin is absent or deficient, blood sugar levels remain high after a meal because glucose is unable to enter most tissue cells. DIABETES Type I diabetes mellitis (insulindependent) afflicts 750, 000 Americans. Autoimmune disease (the insulin secreting beta cells of the Islets of Langerhans are attacked by immune cells) Insulin is not produced or secreted, requiring regular insulin injections. DIABETES Type II diabetes mellitis (non-insulin-dependent) afflicts 7.5 million Americans Insulin resistance - Insulin is usually produced but the receptors do not respond. Loss of receptors possible – can have all the insulin there, but can’t absorb it. DIABETES & HEREDITY Heredity plays a role - an estimated 30% of Americans carry a gene that predisposes them to Type II diabetes. Lifestyle play a role - Type II diabetics are almost always obese and sedentary. Adipose tissue produces a hormone-like chemical that may prevent uptake of insulin PINEAL GLAND Secretes melatonin: Production stimulated by the hypothalamus Sets daily = circadian rhythms. Melatonin secretion increases with darkness and peaks in middle of night. MELATONIN The Midnight Sun Melatonin secretion has been linked to seasonal affective disorder (SAD) in people living in northern latitudes like Alaska. Melatonin is elevated in the winter months, and it may lead to depression, long bouts of sleeping, and eating binges. Sun lamps with a full spectrum of light are helpful therapy for some people. Thymus Gland & Hormones of the Immune System Secretes thymosins that aid in the maturity of lymphocytes inside the lobules of the thymus. Hormones of Digestion & Sex Digestion - gut hormones – ex Gastrin & fullness Sex hormones . . . . 1. Testes 2. produce androgens (testosterone) Puberty - secondary sexual characteristics such as Pubic hair, Muscular strength, Deepening of voice Ovaries produce estrogens and progesterone. Puberty - secondary sexual characteristics such as Pubic hair, Breast development, Widening of hips, onset of menstrual cycle Effects of Anabolic Steroids 1995 1997 2002 2005 Gynecomastia Severe Acne Accelerated Balding Homeostasis – the Balance Hypothalamus produces ADH and thus regulates blood osmolarity (osmotic balance) Endocrine system controls secretion of epinephrine and norepinephrine and thus controls fight or flight responses. Controls blood calcium levels. Muscle contraction. Insulin encourages uptake of glucose by cells and storage of glucose as glycogen in the liver and muscles.