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Transcript
Chemical Signals in Animals • 2 communication systems in body. • 1Nervous system, 2endocrine system. • Endocrine system - glands and tissues that secrete hormones, chemical messengers produced by cells to act on other cells. http://scienceblogs.com/clock/upload/2006/06/endocrine%20system.jpg • Some hormones act on nearby cells (paracrine signals) others on same cells that made them (autocrine signal). • Signals in endocrine system take longer to reach destination (carried by blood), longer lasting than nervous impulses. http://home.earthlink.net/~dayvdanls/paracrine.gif • Endocrine glands secrete hormones directly into bloodstream. • Exocrine secretions do not contain hormones; released through ducts into body compartment. • Example - pancreas in digestion. http://www.daviddarling.info/images/exocrine_gland_types.gif • Hormones classified into 2 groups: steroid hormones, peptide hormones. • Both must bind to protein receptor on target cell, peptide hormones must bind to receptors on cell surface since they cannot cross membrane. • Causes signal to be transmitted to inside of cell. http://web.indstate.edu/thcme/mwking/epinephrinephosphorylase.gif • Signal can activate 2nd messengers, which amplify signal and alter cell activities - called signal transduction cascade because process amplified as it continues down path. • Steroid hormones usually smaller and can pass through membrane. • Most come from cholesterol and usually enter nucleus of cell, altering protein synthesis (transcription). • Steroid hormones not stored, unlike protein hormones - need to be regulated in order to be secreted. http://fig.cox.miami.edu/~cmallery/150/memb/c11x10hormone-receptors2.jpg Endocrine glands • Regulation of production and secretion of hormones done through feedback loop. • Some hormones regulate release of other hormones. • 1Hypothalamus and pituitary – found in forebrain, located above pituitary gland. • Pituitary has 2 parts: anterior pituitary, posterior pituitary. • Posterior - vasopressin (antidiuretic hormone or ADH) - acts on kidney to conserve water; oxytocin - aids in childbirth. http://www.becomehealthynow.com/images/organs/nervous/glakgar_pit_hypothalamus.jpg • Hormones made in hypothalamus, pass through posterior pituitary secreted. • Anterior pituitary regulated by hypothalamus through portal blood circulation - carries blood directly from hypothalamus to pituitary. http://www.brainexplorer.org/brain-images/hypothalamus.jpg • Hypothalamus stimulated releasing factors into portal blood circulation carried to pituitary cause release of hormone from anterior pituitary. • Growth hormone promotes growth in body tissues. http://www.3dscience.com/img/Products/Images/clip_art/endocrine_hypothalamus_pituitary_web.jpg • Thyroid stimulating hormone (TSH) stimulates thyroid to secrete thyroxin. • Adrenocorticotrophic hormone (ACTH) stimulates adrenal cortex to secrete corticosteroids in response to stress. http://media.allrefer.com/s1/l/t0200300-thyroid-gland.jpg • Prolactin - responsible for milk production. • Follicle-stimulating hormone (FSH) promotes maturation of seminiferous tubules in males, ovaries in females. • Luteinizing hormone (LH) promotes testes to secrete testosterone in males; causes ovulation of egg in females. http://www.discount-herbal-nutritional-supplements.com/weight_loss_supplements/images/brain2.gif • Endorphins act on central nervous system to block pain signaling (like opiates). • 2Thyroid gland – thyroxine accelerates metabolism. • Person deficient can develop goiter, lethargy, obesity. • Hyperthyroidism causes profuse sweating, weight loss, increased BMR. http://www.hoslink.com/encocrineimages/hyperthyroid1.jpg • Thyroxine secretion stimulated by hypothalamus in response to environment (like cold), acts on thyroid gland. • Thyroid gland also produces calcitonin - regulates calcium concentration in blood. http://www.cvm.okstate.edu/instruction/mm_curr/histology/HistologyReference/hrendo7.jpg • Calcitonin increases stimulates bone formation, decreases bone destruction. • Calcitonin opposed by parathyroid hormone. • 3Parathyroid glands – located on backside of thyroid gland, secretes parathyroid hormone - regulates calcium, phosphate balance between blood, other tissue. http://cyber.law.harvard.edu/blogs/static/heydan/parathyroid.jpg • Increased parathyroid hormone increase bone resorption, elevates plasma calcium. • Decreased calcium in blood causes secretion of parathyroid hormone which increases activity of osteoclasts (bone breaking cells) remodels bones to release calcium. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • 4Pancreas – performs both exocrine, endocrine functions. • Endocrine function occurs in islets of Langerhans which contain alpha and beta cells that secrete glucagon and insulin. • Insulin stimulates muscles and other cells to release glucose from blood. http://images.medicinenet.com/images/illustrations/pancreas.jpg • Causes muscles and liver to convert glucose to glycogen (storage form of glucose). • Glucagon responds to low levels of blood glucose - stimulates breakdown of glycogen to glucose. • Diabetics cannot control levels of insulin. • 5Adrenal glands – found on top of kidneys, consist of adrenal cortex on exterior + adrenal medulla on inside of gland. • Medulla responsible for epinephrine and norepinephrine in response to stress. http://training.seer.cancer.gov/module_anatomy/images/quiz_dd_adrenal_gland.jpg • Epinephrine responsible for adrenaline release as well as causing blood to shunt away from skin, digestive organs, kidneys; increases blood flow to heart, brain, skeletal muscle. • Also increases metabolic activity. http://services.epnet.com/GetImage.aspx/getImage.aspx?ImageIID=4680 • Cortex responsible for secretion of corticosteroids - regulated by nervous system in response to stress, 3 types. • AGlucocorticoids help to raise blood glucose levels. • High doses help in inflammation response. http://www.stanford.edu/group/hopes/treatmts/lifestyleandhd/f_an1hpaaxis.jpg • BMineral corticoids - promote reabsorption of Na+, excretion of K by kidneys. • CSex hormones – androgens responsible in part for female sex drive. • 6Ovaries, Testes - testes produce testosterone in males, estrogen and progesterone in females. • 7th week of development, information on Y chromosome (if present) starts to produce testosterone. • Absent - female hormones are produced. • ATestes – releases androgens (like testosterone) responsible for production of sperm and secondary male sex characteristics. • BOvaries – secrete estrogen and progesterone. http://www.redhotflush.co.uk/images/cartoons/hormones.jpg • 1Estrogen responsible for stimulating lining of uterus to grow and secondary sex characteristics of females. • 2Progesterone responsible for promoting lining of uterus to grow. http://www.lef.org/magazine/mag2006/images/apr2006_report_prog_02_big.jpg • 7Pineal gland - small mass of tissue near center mammalian brain. • Secretes melatonin - aids in reproduction and cycle of light and dark. http://www.rickrichards.com/chakras/pituitary_brain2a.jpg