1 2 3 4 5 6 BIO 1102 Lec. 9 (Guided): Chapter 13 The Endocrine System The Endocrine System Controls many body functions through chemical signals Hormones Carried in blood stream Affect target cells Composed of many throughout the body Functions of hormones: Homeostasis Growth and Development Reproduction Energy production, storage, and use Behavior Target cells only respond to specific signals Different target cells have different kinds of receptors in their membranes or cytoplasm 2 Categories of Hormones based on their structure and mechanism of action: Steroid soluble Diffuse across cell membrane and enter cell, and even the nucleus Nonsteroid Not soluble Bind to receptors on Changes the shape of a protein in the membrane, resulting in changes within the cell Opening of ion channels, or converting inactive proteins to active state Levels of hormone in blood fluctuate Controlled by feedback loops The endocrine gland acts as the Sometimes the ultimate control center is the brain The hormone is the pathway between the control center and the effectors Effectors are the hormone s target cells, tissues, or organs Self-adjusting and stable 7 Fluctuate as part of natural biorhythm Some hormones may also fluctuate in response to external stimuli, such as danger or stress Not part of a negative feedback loop 1
8 9 10 11 12 The Pituitary Gland Small, pea-sized gland under brain Anterior and posterior sides Anterior Pituitary Produces 6 hormones Production and release controlled by Hypothalamus monitors blood (hormones, nutrients, ions, etc.) If cells in hypothalamus are activated, they stimulate neurons These produce hormones that control the anterior pituitary s production and release of hormones hormones (RH) and hormones (IH) Growth Hormone (GH) Produced in Production triggered by a releasing hormone produced in hypothalamus (GH-RH) GH stimulates growth by increasing and of cells Especially bone and muscle More GH produced when Higher levels in childhood taller, bigger child Levels of GH in blood highest during and Thyroid-Stimulating Hormone (TSH) Produced by Controlled by Stimulate release of thyroid hormone (thyroxine) Negative feedback loop; when low levels of thyroxine detected, TSH-RH secreted by hypothalamus One of major functions of thyroid hormones: stimulate break down of to produce energy and heat ACTH (adrenocorticotropic hormone) Produced by Controlled by via release of ACTH-RH Target of ACTH: of adrenal gland 2
Cells here produce hormones called (e.g. cortisol) Increase blood glucose, maintain homeostasis ACTH-RH also increases under 13 Gonadotropins Two hormones produced by Follicle-stimulating hormone Luteinizing hormone Affect the gonads (discussed in chapter on reproduction) Prolactin Stimulates Release of prolactin triggered by suckling, which sends impulses to hypothalamus, which in turn releases P-RH 14 15 16 Posterior Pituitary Releases 2 hormones: Stimulates pumping of milk from glands in breasts Controls contraction of smooth muscles around glands Stimulated by suckling Also stimulates muscle contractions during birth Regulates water balance Increases water absorption by kidneys Initially produced by neurosecretory cells in Travel down axons to posterior pituitary Stored there, until eventually released Thyroid Gland Located in neck Produces 3 hormones: 17 18 T3 and T4 increase breakdown of glucose, and stimulate cell growth and development 3
If too little T3 and T4 produced Decreased metabolic rate Feeling cold and tired Slow heartbeat rate Treated using pills containing thyroid hormones 19 20 Excess thyroid activity Elevated metabolism Excessive sweating due to overheating Thin Nervousness and anxiety Difficulty sleeping Increased heart rate Treatments: drugs that block function of thyroid hormones surgery to remove part of thyroid (if it has become cancerous) Radioactive iodine (accumulates in the thyroid and damages cells that produce T3 and T4) Calcitonin Produced in Promotes bone Lowers blood calcium by stimulating bone formation and inhibiting action of Negative feedback loop: If blood calcium levels are high, calcitonin secretion increases, which reduces blood calcium levels Calcitonin secretion decreases as blood calcium levels fall 21 Parathyroid Glands 4 nodules embedded in thyroid gland Produce (PTH) Increases blood levels When blood levels fall, secretion of PTH is stimulated Works to increase blood calcium by breaking down, or increasing calcium absorption in intestines Vitamin also important in blood calcium regulation Increases calcium absorption in intestines Increases efficiency of PTH in breaking down bone Too much PTH: excessive loss of calcium from bone and teeth 4
22 23 24 25 The Pancreas Located below the stomach Produces the hormones and, as well as digestive enzymes Insulin Stimulates by body cells Stimulates synthesis of by liver and muscle cells Glycogen: composed of many glucose molecules; used to store glucose for later use (i.e. between meals) Stimulates production Stores energy Glucagon Opposite effect of insulin blood glucose Breaks down in liver Helps maintain proper glucose levels in blood Secretion regulated by negative feedback Decrease in blood glucose increased glucagon secretion by pancreas 26 Diabetes 2 Types: Type I Diabetes Early-onset diabetes Due to damage to the May be an autoimmune disorder; may also result from viral infection or exposure to pollutants Insulin production varies from slightly reduced to completely suppressed 27 Type II Diabetes Late-onset diabetes Occurs most often in people over 40, but increasing among young people Pancreas produces normal or above-normal levels of insulin Target cells are unresponsive to insulin Often associated with 5
28 29 30 31 32 Symptoms of both types of Diabetes Excess and Feeling tired and weak Weight loss and blurred vision Bacterial infections of the Treatments Type I: injections of insulin Eating meals and snacks at regular intervals to maintain blood glucose levels Type II: Insulin injections may help in some cases, but does not cure the disease can often resolve the problem Diet and exercise Eliminate foods high in sugar Risks and Complications Type I Diabetes: Diabetic comas as a result of missing injections or skipping meals Cells become starved of glucose, and begin breaking down fat Too much fat breakdown results in release of toxic chemicals Insulin shock Overdose of insulin Reduces blood glucose levels Tremor, fatigue, sleepiness due to lack of glucose in brain Long term effects can include: Loss of vision Nerve damage Kidney failure Gangrene The Adrenal Glands Located above the 2 zones of the adrenal glands Central zone = adrenal Outer zone = adrenal 33 6
Hormones of the adrenal medulla Adrenalin (aka ) Noradrenalin (aka ) Both secreted under Effects: Elevated blood Increased and Reduced blood flow to intestines; increased flow to skeletal muscles Increased mental alertness Fight-or-flight response 34 Hormones of the Adrenal Cortex Glucocorticoids (discussed previously in Pituitary section) Help maintain blood levels Most important: Mineralocorticoids Regulate ion concentrations in blood and tissue fluids Sodium and potassium levels Most important mineralocorticoid:, which stimulates cells in the kidney to reabsorb sodium and water into the bloodstream 35 36 Diseases of Adrenal Glands Addison s Disease Autoimmune disorder; cells in destroyed by immune system Lack of cortisol production upsets glucose regulation Lack of aldosterone results in low blood pressure and sodium Weight loss, fatigue, weakness Can be treated with hormones in pill form Endocrine Disruptors Chemicals that act like hormones Found in many plastics, conventionally grown meats treated with growth hormones, detergents, etc. BPA common in hard, clear plastics (#7) also in epoxy resins that line food cans Linked to diabetes, obesity, and cancer in lab animals May be leading to decreased sperm count in men May increase cancer risks and other health problems, according to recent (2018) research: https://www.ewg.org/news-and-analysis/2018/04/new-research-links-bpa-breastcancer-lab-animals-fda-downplays-concerns#.wwx39o4vz3g 7
37 38 39 BPA was banned from baby bottles and sippy cups in Canada in 2008, and in the US in 2012 Still found in some products #7 polycarbonate plastic contains BPA Tupperware became BPA free in 2010 Resins that line food cans often contain BPA Although is being removed from many canned food liners, still present in about 40%: https://www.youtube.com/watch?v=zoj72ckcy3u Bonus Activity Describe the cascade of hormonal events that occur to maintain homeostasis when: 1) You go hiking on a hot day and become dehydrated through sweating 2) Your body senses its circulating thyroid hormone levels are too low 3) You ve just eaten a donut and your body senses a rise in blood glucose levels Break 8