Lecture #19 Date________ Chapter 44 ~ Regulating the Internal Environment.
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Transcript of 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
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
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
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
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
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
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
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)
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
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 +
Collecting Duct
• Carries filtrate through the medulla to the renal pelvis
• Reabsorbs NaCl, urea, and water
Water Conservation in Kidney
• Creates hyperosmotic urine
• Conserves water through both active and passive processes
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