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Lecture #19 Date________

Lecture #19 Date________. Chapter 44 ~ Regulating the Internal Environment. Homeostasis : regulation of internal environment. Thermoregulation internal temperature Osmoregulation solute and water balance Excretion nitrogen containing waste.

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Lecture #19 Date________

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  1. Lecture #19 Date________ • Chapter 44 ~ Regulating the Internal Environment

  2. Homeostasis: regulation of internal environment • Thermoregulation internal temperature • Osmoregulation solute and water balance • Excretion nitrogen containing waste

  3. Regulation of body temperature • Thermoregulation • 4 physical processes: • Conduction~transfer of heat between molecules of body and environment • Convection~transfer of heat as water/air move across body surface • Radiation~transfer of heat produced by organisms • Evaporation~loss of heat from liquid to gas • Sources of body heat: • Ectothermic: determined by environment • Endothermic: high metabolic rate generates high body heat

  4. Regulation during environmental extremes • Torpor ~ low activity; decrease in metabolic rate • 1- Hibernation long term or winter torpor (winter cold and food scarcity); bears, squirrels • 2- Estivation short term or summer torpor (high temperatures and water scarcity); fish, amphibians, reptiles • Both often triggered by length of daylight

  5. Water balance and waste disposal • Osmoregulation: management of the body’s water content and solute composition • Nitrogenous wastes: breakdown products of proteins and nucleic acids; ammonia-very toxic • Deamination~ • Ammonia: most aquatic animals, many fish • Urea: mammals, most amphibians, sharks, bony fish (in liver; combo of NH3 and CO2) • Uric acid: birds, insects, many reptiles, land snails

  6. Osmoregulators • Osmoconformer: no active adjustment of internal osmolarity (marine animals); isoosmotic to environment • Osmoregulator: adjust internal osmolarity (freshwater, marine, terrestrial) • Freshwater fishes (hyperosmotic)- gains water, loses; excretes large amounts of urine salt vs. marine fishes (hypoosmotic)- loses water, gains salt; drinks large amount of saltwater

  7. Water Loss in Land Animals • Terrestrial organisms must also regulate their water levels • Adaptations include: • Waxy cuticle in plants • Shells of land snails • Waxy layers of insect exoskeleton • Layers of dead skin • Being nocturnal • Most loose water from moist surface areas of gas exchange, urine, feces, and skin • Must gain water from diet or through metabolism

  8. Excretory Systems • Production of urine by 2 steps: Filtration (nonselective) and Selective Reabsorption (secretion of solutes) • Protonephridia ~ flatworms (“flame-bulb” systems) • Metanephridia ~ annelids (ciliated funnel system) • Malpighian tubules ~ insects (tubes in digestive tract) • Kidneys ~ vertebrates

  9. Kidney Functional Units • Renal artery/vein: kidney blood flow • Ureter: urine excretory duct • Urinary bladder: urine storage • Urethra: urine elimination tube • Renal cortex (outer region) • Renal medulla (inner region) • Nephron: functional unit of kidney, approx. 1 million per kidney) • Cortical nephrons (confined to renal cortex; 80%) • Juxtamedullary nephrons (extend into renal medulla; 20%; only in mammals and birds, important in water conservation – hyperosmotic urine)

  10. Nephron Structure • Afferent arteriole: supplies blood to nephron from renal artery • Glomerulus: ball of capillaries • Efferent arteriole: blood from glomerulus • Bowman’s capsule: surrounds glomerulus • Proximal tubule: secretion & reabsorption • Peritubular capillaries: from efferent arteriole; surround proximal & distal tubules • Loop of Henle: water & salt balance • Distal tubule: secretion & reabsorption • Collecting duct: carries filtrate to renal pelvis

  11. Basic Nephron Function

  12. Proximal Tubule, Loop of Henle, Distal Tubule • PT – reabsorb HCO3-, NaCl, water, nutrients, and K+ ions; secrete H+ and NH3 • Decending L of H – reabsorb water • Ascending L of H – reabsorb NaCl • DT – reabsorb NaCl, water, and HCO3-; secrete K + and H +

  13. Collecting Duct • Carries filtrate through the medulla to the renal pelvis • Reabsorbs NaCl, urea, and water

  14. Water Conservation in Kidney • Creates hyperosmotic urine • Conserves water through both active and passive processes

  15. Kidney regulation: hormones • Antidiuretic hormone (ADH) ~ secretion increases permeability of distal tubules and collecting ducts to water (H2O back to body); inhibited by alcohol and coffee • Juxtaglomerular apparatus (JGA) ~ reduced salt intake--->enzyme renin initiates conversion of angiotensin (plasma protein) to angiotensin II (peptide); increase blood pressure and blood volume by constricting capillaries • Angiotensin II also stimulates adrenal glands to secrete aldosterone; acts on distal tubules to reabsorb more sodium, thereby increasing blood pressure (renin-angiotension-aldosterone system; RAAS) • Atrial natriuretic factor (ANF) ~ walls of atria; inhibits release of renin, salt reabsorption, and aldosterone release

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