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Transcript
CHAPTER 45 CHEMICAL SIGNALS IN ANIMALS QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. The endocrine system and the nervous system are structurally, chemically, and functionally related Why have a hormonal/endocrine system? QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Homeostasis regulation of body functions - keeps body “ON TRACK” • Endocrine glands: QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see thi s picture. Ductless glands, release hormones into BLOODSTREAM • Exocrine glands: Glands with ducts, release enzymes into a lumen/cavity; Ex. salivary glands • Paracrine secretions: Local regulators Local regulators affect neighboring target cells- Paracrine secretions • Growth factors: proteins and polypeptides that stimulate cell division • Nitric oxide (NO)- neurotransmitter, it kills bacteria and cancer cells, it dilates the walls of blood vessels (Viagra!!!) • Prostaglandins secreted by the placenta stimulate uterine contractions during childbirth; important in inflammatory response • Hormones are chemical signals. The endocrine system consists of: QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Endocrine cells- hormonesecreting cells and Endocrine glandshormone-secreting organs. Secrete their hormones into blood stream and affect target cells • Specific target cells respond to specific hormones = receptors involved and second messenger system (chp 11). Neurosecretory cells (neurons that can produce hormones) secrete hormones into the blood. Located in hypothalamus Epinephrine - can signal nerves and act as a hormone Feedback regulation is a feature of both the endocrine and nervous systems (negative and positive feedback loops). • Negative regulation - hormone decreases the stimulus causing its production: • Calcium can be stored in bone or released to cells via blood (like glycogen-glucose) • Blood Calcium level high (stimulus) • Thyroid makes calcitonin • Enters blood • Calcium goes from blood to bone • Calcium level falls (stimulus decreases) • Hormone release causes stimulus to decrease- negative feedback Positive feedback loop- Stimulus makes the hormone to be released, and hormone release increases stimulus strength • Sucking of baby (stimulus) • Hypothalamus makes Oxytocin • Enters blood QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Smooth muscle contraction at nipple releasing milk • Baby sucks more!! • Positive feedback- not seen as often as negative feedback Invertebrates: Ecdysone- promotes the development of adult features. Neurosecretory cells in the brain produce brain hormone (BH), which regulates the secretion of ecdysone. •Juvenile hormone (JH) promotes the retention of larval characteristics. Fig. 45.2 Signal transduction - Most chemical signals bind to plasma-membrane proteins, initiating signal transduction pathways like G protein and phosphorylation cascade (water soluble hormones) • Signaltransduction pathways allow for small amounts of a hormone to have a large effect. Fig.11.16 Signal transduction Steroid hormones, thyroid hormones, and some local regulators enter target cells and bind to intracellular receptors in the cytoplasm. Next they activate transcription factors - these bind to DNA in the nucleus and cause mRNA to be produced which in turn produces proteins (lipid soluble) Water soluble Hormones: Lipid soluble Hormones: Bind to plasma membrane receptors on target cells Enter target cells and bind to intracellular receptors Examples: Insulin, epinephrine Examples: estrogen, progesterone, vitamin D, NO. Leads to activation of G proteins, second messengers (cAMP), protein kinases enzymes that activate various proteins including some transcription factors May lead to changes in DNA transcription Final effect - protein activation or synthesis Usually, the intracellular receptor activated by a hormone is a transcription factor. Leads to changes in DNA transcription Final effect - protein synthesis Fig. 45.3b • Different signal-transduction pathways in different cells can lead to different responses to the same signal. Fig. 45.4 CHAPTER 45 CHEMICAL SIGNALS IN ANIMALS Section C: The Vertebrate Endocrine System 1. The hypothalamus and pituitary integrate many functions of the vertebrate endocrine system 2. The pineal gland is involved in biorhythms 3. Thyroid hormones function in development, bioenergetics, and homeostasis 4. Parathyroid hormone and calcitonin balance blood calcium 5. Endocrine tissues of the pancreas secrete insulin and glucagon, antagonistic hormones that regulate blood glucose 6. The adrenal medulla and adrenal cortex help the body manage stress 7. Gonadal steroids regulate growth, development, reproductive cycles, and sexual behavior Introduction Tropic hormones - produced by hypothalamus and pituitary gland MASTER GLAND>target other endocrine glands and are important for chemical coordination. • Humans have nine endocrine glands. Fig. 45.5 Hypothalamus Tropic Hypothalamus and Hormones: pituitary integrate endocrine B) Releasingsystem hormones •produced A) Neurosecretory by cells of the stimulate hypothalamus hypothalamus the anterior pituitary produce hormones-to (adenohypophysis) ADH hormones. and Oxytocin. secrete (FSH, Reach posterior TSH, ACTH) pituatary gland for C) Inhibiting hormones storage prevent the anterior pituitary from secreting hormones. D) Nontropic Hormones Prolactin, MSH, Hypothalamus and pituitary integrate endocrine system • A) Neurosecretory cells of the hypothalamus produce hormonesADH and Oxytocin. Reach posterior pituatary gland for storage • Hormones manufactured by the hypothalamus and released by the posterior pituitary. • Oxytocin: a peptide. • Stimulates contraction of the uterus (birthing/parturition) and mammary glands (for milk). • Secretion regulated by the nervous system. • Antidiuretic hormone (ADH): a peptide (in excretion chapter 44) • Promotes retention of water by the kidneys. • Secretion regulated by water/salt balance. Pituatary hormones: Fig. 45.6b Table 45.1 (continued) Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Anterior pituitary hormones. • Growth hormone (GH): a protein. • Stimulates growth and metabolism. • Secretion regulated by hypothalamic hormones. • Acts directly on tissues or acts via growth factors. • Gigantism: excessive GH during development. • Acromegaly: excessive GH production during adulthood. • Hypopituitary dwarfism: childhood GH deficiency. • Thyroid-stimulating hormone (TSH): a glycoprotein. • Stimulates thyroid gland. • Secretion regulated by thyroxine in blood. • Secretion regulated by hypothalamic hormones. • Adrenocorticotropic hormone (ACTH): a peptide • Stimulates adrenal cortex secretion of glucocorticoids • Secretion regulated by glucocorticoids and hypothalamic hormones. • Prolactin (PRL): a protein. • Stimulates milk production and secretion. • Secretion regulated by hypothalamic hormones. • Gonadotropins: glyocoproteins. • Follicle-stimulating hormone (FSH). • Stimulates production of sperm and ova. • Secretion regulated by hypothalamic hormones. • Luteinizing hormone (LH). • Stimulates ovaries and testes. • Secretion regulated by hypothalamic hormones. • Melanocyte-stimulating hormone (MSH): a peptide. • May play a role in fat metabolism. • Endorphins: peptides. • Inhibit pain perception. • Effects mimicked by heroin and other opiate drugs. 2) The pineal gland is a small mass of tissue near the center of the mammalian brain. • The pineal gland secretes the hormone, melatonin, an amine. • Involved in biological rhythms associated with reproduction. • Secretion regulated by light/dark cycles. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Thyroid gland: • Produces thyroxine hormone 3. Thyroid hormones function in development, bioenergetics, and homeostasis • The thyroid gland of mammals consists of two lobes located on the ventral surface of the trachea. • Triiodothyronine (T3) and thyroxine (T4): amines. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Stimulates and maintain metabolic processes. • Secretion regulated by TSH hormones. Fig. 45.8 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 45.9 Thyroid in Amphibians: QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Thyroid hormone functions: • A) metamorphosis in amphibians QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • B) Bone and brain development in some other animals • C) Homeostasis in humans - metabolism control • Hyperthyroidism - Grave’s diseaseeyes protrude • Palpitations • Heat intolerance • Nervousness • Insomnia QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Increased bowel movements • Light or absent menstrual periods • Fatigue • Fast heart rate • Trembling hands • Weight loss • Muscle weakness • Sweating QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Hypothyroidism An insufficient amount of thyroid hormones is known as hypothyroidism. Infants: cretinism. Adults: weight gain, lethargy, cold intolerance. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Goiter: often associated with iodine deficiency (no negative feedback!) 4) Parathyroid- embedded in the surface of the thyroid gland. Parathyroid Hormone and Calcitonin: Opposite effects- regulate calcium levels QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. -Secretion regulated by calcium in blood. • Parathyroid hormone (PTH), a peptide. • Raises blood calcium levels. • Causes osteoclasts to break down bone, releasing Ca2+ into the blood. • Stimulates the kidneys to reabsorb Ca2+. • Stimulates kidneys to convert vitamin D to its active form. • Hypoparathyoidism: tetany.- convulsive contraction of muscles 5) Endocrine tissues of the pancreas secrete insulin and glucagon, antagonistic hormones that regulate blood glucose • The pancreas has both endocrine and exocrine functions. • Exocrine function: secretion of bicarbonate ions and digestive enzymes. • Endocrine function: insulin and glucagon secreted by islets of Langerhans. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Fig. 45.10 •Glucagon: a protein secreted • Insulin: a protein secreted by beta cells . by alpha cells. • Lowers blood glucose levels. • Stimulates all body cells (except brain cells) to take up glucose from blood. • Slows glycogen breakdown. • Inhibits gluconeogenesis. • Secretion regulated by glucose in blood (negative feedback). •Raises blood glucose levels. • Inhibits cells from taking up glucose from the blood •Stimulates glyogen breakdown in the liver and skeletal muscle. •Stimulates gluconeogenesis •Secretion regulated by glucose in blood (negative feedback QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Hypoinsulinism: diabetes mellitus- “honey water” • Hereditary factors and obesity play a role in its development. • High blood sugar levels – sugar excreted in the urine. • Symptoms: excessive urination and excessive thirst. • If severe: fat substitutes for glucose as major fuel source production of acidic metabolites life threatening lowering of blood pH. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Type I diabetes mellitus (insulin-dependent diabetes). • Autoimmune disorder. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Usually appears in childhood. • Treatment: insulin injections. • Type II diabetes mellitus (noninsulin-dependent diabetes). • Usually due to target cells having a decreased responsiveness to insulin. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Usually occurs after age 40 – risk increases with age, weight, stress. • Accounts for over 90% of diabetes cases. 6) The adrenal medulla and adrenal cortex help the body manage stress • The adrenal glands are located adjacent to the kidneys. • The adrenal cortex is the outer portion. • The adrenal medulla is the inner portion. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a QuickTime™ and a decompressor TIFF (Uncompressed) TIFF (Uncompressed) decompressor are needed to see this picture. are needed to see this picture. • Adrenal medulla. • Developmentally and functionally related to the nervous system. • Epinephrine (adrenaline) and norepinephrine (noradrenaline). • Flight or fight response • Increased sugar in blood • Adrenal cortex reacts to stress- especially long term. • Secretes corticosteroids • Glucocorticoids. • Raises blood glucose level. • Secretion regulated by ACTH (negative feedback). • Abnormally high doses are administered as medication to suppress the inflammation response • Blood routed to skeletal muscles, heart, brain (and not skin, digestive organs) • Mineralocorticoids (example: aldosterone, which affects salt and water balance). • Increased heart rate, stroke volume, breathing, dialtion of bronchioles… • Promotes reabsorption of Na+ and excretion of K+ in kidneys. • Secretion regulated by K+ in blood. Fig. 45.14 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • A third group of corticosteriods are sex hormones. • Androgens secreted by the adrenal cortex may account for the female sex drive. • The adrenal cortex also secretes small amounts of estrogens and progesterone. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 7. Gonadal steroids regulate growth, development, reproductive cycles, and sexual behavior • Testes. • Androgens (example: testosterone): steroids. • Supports sperm formation. • Promote development and maintenance of male sex characteristics. • Secretion regulated by FSH and LH. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Ovaries secrete estrogens and progesterone. • Estrogens: steroids. • Stimulate uterine lining growth. • Promote development and maintenance of female sex characteristics. • Secretion regulated by FSH and LH. • Progestins (example: progesterone): steroids. • Promotes uterine lining growth. • Secretion regulated by FSH and LH. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings