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1 Chapter 25 Hormones HORMONES: AN OVERVIEW 2 • Hormones are produced by most plants and animals. • Animal hormones – are made and secreted mainly by endocrine glands, – are usually carried by the circulatory system, and – communicate regulatory messages to specific sites in the body. PowerPoint® Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition – Eric J. Simon, Jean L. Dickey, and Jane B. Reece Lectures by Edward J. Zalisko © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. HORMONES: AN OVERVIEW • The endocrine system – consists of all hormone-secreting cells and – is the body’s main system for internal chemical regulation. 3 HORMONES: AN OVERVIEW • Endocrine cells secrete into the bloodstream hormones that – can affect many cells in many different body organs but – only affect target cells, cells that have receptors for that specific hormone. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 4 5 Figure 25.1 6 Endocrine cell Membraneenclosed sacs Blood vessel Hormone molecules Target cell Receptor protein Adrenal glands (type of endocrine gland), which sit atop the kidneys Blast Animation: Signaling: Endocrine Right click slide / select “Play” © 2013 Pearson Education, Inc. Figure 25.1a 7 Endocrine cell HORMONES: AN OVERVIEW • There are two general mechanisms by which hormones trigger changes in target cells: Target cell 1. Water-soluble hormones trigger responses without ever entering their target cells. Receptor protein Membraneenclosed sacs Hormone molecules Blood vessel © 2013 Pearson Education, Inc. 8 9 Figure 25.2-1 10 Watersoluble hormone Receptor protein 1 Target cell Plasma membrane Nucleus Animation: Water-Soluble Hormone Right click slide / select “Play” © 2013 Pearson Education, Inc. Figure 25.2-2 11 Watersoluble hormone Receptor protein 1 Target cell Relay molecules 2 Plasma membrane Signal transduction pathway Figure 25.2-3 12 Watersoluble hormone Receptor protein 1 Target cell 2 Plasma membrane Signal transduction pathway Relay molecules Cytoplasmic response or 3 Nucleus Nucleus Gene regulation HORMONES: AN OVERVIEW 13 14 2. Lipid-soluble hormones trigger responses after entering the target cell. Blast Animation: Signaling via Steroid Hormones Right click slide / select “Play” © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 15 Figure 25.3-1 16 Lipidsoluble hormone 1 Target cell Nucleus Animation: Lipid-Soluble Hormone Right click slide / select “Play” © 2013 Pearson Education, Inc. Plasma membrane Figure 25.3-2 17 Figure 25.3-3 Lipidsoluble hormone 18 Lipidsoluble hormone 1 Target cell 1 Target cell Plasma membrane 2 Plasma membrane 2 Receptor protein Receptor protein Nucleus Nucleus Figure 25.3-4 19 Lipidsoluble hormone 1 Target cell 3 Hormonereceptor complex THE HUMAN ENDOCRINE SYSTEM • The human endocrine system consists of about a dozen major glands that may have Plasma membrane – only endocrine functions or 2 Receptor protein Nucleus 4 – endocrine and non-endocrine functions. • The major endocrine glands in humans are spread about the human body. 3 Hormonereceptor complex Gene regulation © 2013 Pearson Education, Inc. 20 Figure 25.4 21 THE HUMAN ENDOCRINE SYSTEM 22 Hypothalamus Pituitary gland • Hormones have a wide range of Thyroid gland Parathyroid glands (embedded within thyroid) – target cells and – effects. Adrenal glands (atop kidneys) Pancreas Ovaries (female) Testes (male) © 2013 Pearson Education, Inc. Table 25.1 23 Table 25.1a 24 Table 25.1b 25 The Pancreas 26 • The pancreas produces two antagonistic hormones that play important roles in managing the body’s energy supplies: 1. insulin, which reduces blood sugar levels and 2. glucagon, which increases blood sugar levels. © 2013 Pearson Education, Inc. Figure 25.9 27 Body cells take up glucose Insulin Pancreas releases insulin 1 Stimulus: Rising blood glucose 2 Blood glucose level falls Liver stores glucose as glycogen 3 • Diabetes mellitus is a serious hormonal disease in which body cells are unable to absorb glucose from the blood because either – there is not enough insulin produced (type 1, or insulin-dependent diabetes) or Glucose level Homeostasis: Normal blood glucose level Glucose level The Pancreas Stimulus: Declining blood glucose – the target cells do not respond normally to insulin (type 2, or non-insulin-dependent diabetes). 4 6 Blood glucose level rises Pancreas releases glucagon 5 Liver breaks down glycogen Glucagon © 2013 Pearson Education, Inc. 28 The Pancreas 29 Figure 25.10 30 • Diabetes affects about 8% of all Americans. • More than 90% of those affected have type 2 diabetes, which is associated with being – overweight and – underactive. • People with diabetes use glucose meters to measure the amount of glucose in the blood. © 2013 Pearson Education, Inc. The Adrenal Glands • The adrenal glands are paired structures resting atop each kidney. • Each adrenal gland consists of two glands: 1. the central adrenal medulla and 31 The Adrenal Glands • The adrenal medulla secretes epinephrine and norepinephrine, hormones that – enable a rapid, short-term response to stress and – produce the “fight-or-flight” response. 2. the outer adrenal cortex. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. 32 33 The Adrenal Glands • Stressful stimuli activate nerve cells in the hypothalamus that send signals to stimulate the adrenal medulla to secrete • The adrenal cortex – is also stimulated by the hypothalamus and – secretes corticosteroid hormones (including glucocorticoids) that provide a slower, longerlasting response to stress. – epinephrine and – norepinephrine. © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 25.11 35 STRESS Adrenal gland Kidney 34 The Adrenal Glands Figure 25.11c 36 Adrenal medulla Adrenal cortex Nerve 1 signals Hypothalamus 3 Nerve cell Releasing hormone Anterior pituitary Adrenal gland Blood vessel Spinal cord (cross section) Nerve cell ACTH Adrenal medulla 4 Adrenal medulla Epinephrine and norepinephrine 2 ACTH Adrenal cortex 5 Corticosteroids Short-term stress response Long-term stress response • Glycogen broken down to glucose; increased blood glucose • Proteins and fats broken down and converted to glucose, leading to increased blood glucose • Increased blood pressure, breathing rate, heart rate, and metabolic rate • Immune system may be suppressed • Change in blood flow patterns, leading to increased alertness and decreased digestive activity Kidney Adrenal cortex Figure 25.11a 37 Figure 25.11b 38 Nerve 1 signals Hypothalamus 3 Releasing hormone Nerve cell Anterior pituitary Blood vessel Spinal cord (cross section) ACTH Nerve cell 4 Adrenal medulla Epinephrine and norepinephrine Adrenal cortex ACTH 5 Corticosteroids 2 Long-term stress response Short-term stress response Figure 25.11d 39 The Gonads Short-term stress response • The gonads secrete sex hormones that • Glycogen broken down to glucose; increased blood glucose – affect growth and development and • Increased blood pressure, breathing rate, heart rate, and metabolic rate – regulate • Change in blood flow patterns, leading to increased alertness and decreased digestive activity Long-term stress response – reproductive cycles and – sexual behavior. • Proteins and fats broken down and converted to glucose, leading to increased blood glucose • Immune system may be suppressed © 2013 Pearson Education, Inc. 40 The Gonads 41 • Estrogens • Males and females have the same three types of sex hormones: – maintain the female reproductive system and 1. estrogens, – promote the development of specific female features, such as breasts and wider hips. 2. progestins, and • Progestins, such as progesterone, are primarily involved in preparing the uterus to support a developing embryo. 3. androgens. © 2013 Pearson Education, Inc. The Gonads • Androgens, mainly testosterone, stimulate the development and maintenance of the male reproductive system. © 2013 Pearson Education, Inc. The Gonads © 2013 Pearson Education, Inc. 43 42