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Lecture #19 Date________

This lecture discusses the regulation of the internal environment, focusing on homeostasis, thermoregulation, and osmoregulation. It covers topics such as the regulation of body temperature, water balance, and waste disposal. The lecture also introduces different excretory systems and their functions, as well as the role of hormones in kidney regulation.

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

  8. 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 • Cortical nephrons (cortex; 80%) • Juxtamedullary nephrons (medulla; 20%)

  9. 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

  10. Basic Nephron Function

  11. Nephron Function, I • Proximal tubule: secretion and reabsorption

  12. Nephron Function, II • Loop of Henle: reabsorption of water and salt • Distal tubule: secretion and reabsorption

  13. Nephron Function, III • Collecting duct: reabsorbs water, salt, some urea

  14. 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 angiotension (plasma protein) to angiotension II (peptide); increase blood pressure and blood volume by constricting capillaries • Angiotension 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

  15. Hormonal Control

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