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Chapter 45: Hormones
- 1. Chapter 45 Hormones: TheBody’s Long- Distance Regulators • Animal hormones are chemical signals that are secreted into the circulatory system and communicate regulatory messages within the body • Hormones reach all parts of the body, but only target cells are equipped to respond. Why?
- 2. Metamorphosis is regulated byhormones Metamorphosis= the hormonal reactivation of development
- 3. • Remodeling • Replacement(respecification) • New structures • Death Larva function: dispersal (sea urchin) or growth (amphibians)
- 4. Eye migration andassociated neuronal changes during metamorphosis of Xenopus laevis Axons cross midline in early Axons do not cross in late Eyes move from prey mode to predator mode (in front for bifocal vision)
- 5.
- 6. If thyroid removed or destroyed remaina tadpole 4- ever. T4 T3
- 7. In the wildremains in juvenile stage because thyroid does not release thyrotropin Give the hormone in the lab and get adult form that is never seen in the wild. Here neoteny = retention of juvenile form with adult gametes
- 8. The endocrine systemand the nervous system act individually and together in regulating an animal’s physiology • Animals have two systems of internal communication and regulation: the nervous system and the endocrine system • The nervous system conveys high-speed electrical signals along specialized cells called neurons • The endocrine system secretes hormones that coordinate slower but longer-acting responses
- 9. Overlap Between Endocrineand Nervous Regulation • The endocrine and nervous systems function together in maintaining homeostasis, development, and reproduction • Specialized nerve cells known as neurosecretory cells release neurohormones into the blood • Both endocrine hormones and neurohormones function as long-distance regulators of many physiological processes
- 10. Control Pathways andFeedback Loops • There are three types of hormonal control pathways: simple endocrine, simple neurohormone, and simple neuroendocrine • A common feature is a feedback loop connecting the response to the initial stimulus • Negative feedback regulates many hormonal pathways involved in homeostasis
- 11. LE 45-2a Target effectors Response Simple endocrinepathway Glycogen breakdown, glucose release into blood Liver Blood vessel Pancreas secretes glucagon ( ) Endocrine cell Low blood glucose Receptor protein Stimulus Pathway Example
- 12. LE 45-2b Target effectors Response Simple neurohormonepathway Stimulus Pathway Example Suckling Milk release Smooth muscle in breast Neurosecretory cell Blood vessel Posterior pituitary secretes oxytocin ( ) Hypothalamus/ posterior pituitary Sensory neuron
- 13. LE 45-2c Target effectors Response Simple neuroendocrinepathway Stimulus Pathway Example Milk production Blood vessel Hypothalamus Sensory neuron Mammary glands Endocrine cell Blood vessel Anterior pituitary secretes prolactin ( ) Hypothalamus secretes prolactin- releasing hormone ( ) Neurosecretory cell Hypothalamic neurohormone released in response to neural and hormonal signals
- 14. Hormones and otherchemical signals bind to target cell receptors, initiating pathways that culminate in specific cell responses • Hormones convey information via the bloodstream to target cells throughout the body • Three major classes of molecules function as hormones in vertebrates: – Proteins and peptides – Amines derived from amino acids – Steroids
- 15. • Signaling byany of these hormones involves three key events: – Reception – Signal transduction – Response
- 16. Cell-Surface Receptors forWater- Soluble Hormones • The receptors for most water-soluble hormones are embedded in the plasma membrane, projecting outward from the cell surface
- 17. LE 45-3 SECRETORY CELL Hormone molecule Signal receptor VIA BLOOD VIA BLOOD TARGET CELL TARGET CELL Signal transduction pathway OR Cytoplasmic response DNA NUCLEUS Nuclear response Receptorin plasma membrane Receptor in cell nucleus DNA NUCLEUS mRNA Synthesis of specific proteins Signal transduction and response Signal receptor Hormone molecule SECRETORY CELL
- 18. • Binding ofa hormone to its receptor initiates a signal transduction pathway leading to responses in the cytoplasm or a change in gene expression • The same hormone may have different effects on target cells that have – Different receptors for the hormone – Different signal transduction pathways – Different proteins for carrying out the response
- 19. LE 45-4 Different receptorsdifferent cell responses Epinephrine α receptor Epinephrine β receptor Epinephrine β receptor Vessel constricts Vessel dilates Intestinal blood vessel Skeletal muscle blood vessel Liver cell Different intracellular proteins different cell responses Glycogen deposits Glycogen breaks down and glucose is released from cell The hormone epinephrine has multiple effects in mediating the body’s response to short-term stress
- 20. Intracellular Receptors forLipid-Soluble Hormones • Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus • Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes
- 21. Paracrine Signaling byLocal Regulators • In paracrine signaling, nonhormonal chemical signals called local regulators elicit responses in nearby target cells • Types of local regulators: – Neurotransmitters – Cytokines and growth factors – Nitric oxide – Prostaglandins
- 22. • Prostaglandins helpregulate aggregation of platelets, an early step in formation of blood clots
- 23. • The hypothalamusand the pituitary gland control much of the endocrine system
- 25. LE 45-6 Testis (male) Ovary (female) Adrenal glands Pancreas Parathyroidglands Thyroid gland Pituitary gland Pineal gland Hypothalamus
- 26. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings Relation Between the Hypothalamus and Pituitary Gland • The hypothalamus, a region of the lower brain, contains neurosecretory cells • The posterior pituitary, or neurohypophysis, is an extension of the hypothalamus • Hormonal secretions from neurosecretory cells are stored in or regulate the pituitary gland
- 27. LE 45-7 Mammary glands, uterinemuscles Hypothalamus Kidney tubules OxytocinHORMONE TARGET ADH Posterior pituitary Neurosecretory cells of the hypothalamus Axon Anterior pituitary
- 28. • Other hypothalamiccells produce tropic hormones, hormones that regulate endocrine organs • Tropic hormones are secreted into the blood and transported to the anterior pituitary, or adenohypophysis • The tropic hormones of the hypothalamus control release of hormones from the anterior pituitary
- 29. LE 45-8 Neurosecretory cells ofthe hypothalamus Endocrine cells of the anterior pituitary Portal vessels Pituitary hormones (blue dots) Pain receptors in the brain Endorphin Growth hormone BonesLiver MSH Melanocytes Prolactin Mammary glands ACTH Adrenal cortex TSH ThyroidTestes or ovaries FSH and LH TARGET HORMONE Hypothalamic releasing hormones (red dots) Tropic Effects Only FSH, follicle-stimulating hormone LH, luteinizing hormone TSH, thyroid-stimulating hormone ACTH, adrenocorticotropic hormone Nontropic Effects Only Prolactin MSH, melanocyte-stimulating hormone Endorphin Nontropic and Tropic Effects Growth hormone
- 30. Posterior Pituitary Hormones •The two hormones released from the posterior pituitary act directly on nonendocrine tissues • Oxytocin induces uterine contractions and milk ejection • Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys Anterior Pituitary Hormones • The anterior pituitary produces both tropic and nontropic hormones
- 31. Tropic Hormones • Thefour strictly tropic hormones are – Follicle-stimulating hormone (FSH) – Luteinizing hormone (LH) – Thyroid-stimulating hormone (TSH) – Adrenocorticotropic hormone (ACTH) • Each tropic hormone acts on its target endocrine tissue to stimulate release of hormone(s) with direct metabolic or developmental effects
- 32. Nontropic Hormones • Nontropichormones produced by the anterior pituitary: – Prolactin: stimulates lactation in mammals but has diverse effects in different vertebrates – Melanocyte-stimulating hormone (MSH) influences skin pigmentation in some vertebrates and fat metabolism in mammals – β-endorphin: inhibits pain
- 33. Growth Hormone • Growthhormone (GH) has tropic and nontropic actions • It promotes growth directly and has diverse metabolic effects • It stimulates production of growth factors
- 34. Nonpituitary hormones help regulatemetabolism, homeostasis, development, and behavior
- 35. Thyroid Hormones • Thethyroid gland consists of two lobes on the ventral surface of the trachea • It produces two iodine-containing hormones: triiodothyronine (T3) and thyroxine (T4)
- 36. Hypothalamus TRH Anterior pituitary TSH Thyroid T3 T4 The hypothalamus and anterior pituitarycontrol secretion of thyroid hormones through two negative feedback loops
- 37. Copyright © 2005Pearson Education, Inc. publishing as Benjamin Cummings Parathyroid Hormone and Calcitonin: Control of Blood Calcium • Two antagonistic hormones, parathyroid hormone (PTH) and calcitonin, play the major role in calcium (Ca2+ ) homeostasis in mammals • The thyroid gland produces calcitonin.
- 38. • Calcitonin stimulatesCa2+ deposition in bones and secretion by kidneys, lowering blood Ca2+ levels • PTH, secreted by the parathyroid glands, has the opposite effects on the bones and kidneys, and therefore raises Ca2+ levels • PTH also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca2+ from food
- 39. LE 45-11 STIMULUS: Rising blood Ca2+ level Thyroidgland releases calcitonin. Calcitonin Stimulates Ca2+ deposition in bones Reduces Ca2+ uptake in kidneys Blood Ca2+ level declines to set point Homoeostasis: Blood Ca2+ level (about 10 mg/100 mL) STIMULUS: Falling blood Ca2+ level Blood Ca2+ level rises to set point Stimulates Ca2+ release from bones PTH Parathyroid gland Stimulates Ca2+ uptake in kidneys Active vitamin D Increases Ca2+ uptake in intestines
- 40. Insulin and Glucagon:Control of Blood Glucose • The pancreas secretes insulin and glucagon, antagonistic hormones that help maintain glucose homeostasis • Glucagon is produced by alpha cells • Insulin is produced by beta cells
- 42. Target Tissues forInsulin and Glucagon • Insulin reduces blood glucose levels by – Promoting the cellular uptake of glucose – Slowing glycogen breakdown in the liver – Promoting fat storage • Glucagon increases blood glucose levels by – Stimulating conversion of glycogen to glucose in the liver – Stimulating breakdown of fat and protein into glucose
- 43. LE 45-12 Beta cellsof pancreas release insulin into the blood. Insulin Liver takes up glucose and stores it as glycogen. STIMULUS: Rising blood glucose level (for instance, after eating a carbohydrate- rich meal) Blood glucose level declines to set point; stimulus for insulin release diminishes. Homeostasis: Blood glucose level (about 90 mg/100 mL) STIMULUS: Dropping blood glucose level (for instance, after skipping a meal) Blood glucose level rises to set point; stimulus for glucagon release diminishes. Liver breaks down glycogen and releases glucose into the blood. Body cells take up more glucose. Alpha cells of pancreas release glucagon into the blood. Glucagon
- 44. Diabetes Mellitus • Diabetesmellitus is perhaps the best-known endocrine disorder • It is caused by a deficiency of insulin or a decreased response to insulin in target tissues • It is marked by elevated blood glucose levels • Type I diabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells • Type II diabetes mellitus (non-insulin-dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors (old age, sigh)
- 45. Adrenal Hormones: Responseto Stress • The adrenal glands are adjacent to the kidneys • Each adrenal gland actually consists of two glands: the adrenal medulla and adrenal cortex
- 46. Catecholamines from theAdrenal Medulla • The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline) • These hormones are members of a class of compounds called catecholamines • They are secreted in response to stress- activated impulses from the nervous system • They mediate various fight-or-flight responses
- 47. Stress Hormones fromthe Adrenal Cortex • Hormones from the adrenal cortex also function in response to stress • They fall into three classes of steroid hormones: – Glucocorticoids, such as cortisol, influence glucose metabolism and the immune system – Mineralocorticoids, such as aldosterone, affect salt and water balance – Sex hormones are produced in small amounts
- 48. LE 45-13 Stress Hypothalamus Anterior pituitary Bloodvessel ACTH ACTH Releasing hormone Nerve cell Nerve cell Long-term stress response Effects of mineralocorticoids: 1. Retention of sodium ions and water by kidneys 2. Increased blood volume and blood pressure Effects of glucocorticoids: 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose 2. Immune system may be suppressed Short-term stress response Effects of epinephrine and norepinephrine: 1. Glycogen broken down to glucose; increased blood glucose 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 5. Change in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity Nerve signalsSpinal cord (cross section) Adrenal gland Kidney