Chapter 44: Regulation of the Internal Environment 1 Figure 44.0 Fox in snow Homeostasis: maintain physiologically favorable internal environment even if external conditions change 2 Figure 44.1 Regulators and conformers Regulator Conformer Same organism may regulate/conform for different factors • Lizard: regulate N concentration, but not temp Regulator Conformer Cost Energy Limit Range Benefit Survive if environment changes Conserve energy Expands range Figure 44.2 A partial energy and material bookkeeping for ten years in the life of a 3 young woman Homeostasis balances mass/energy in/out 4 Figure 44.3 Heat exchange between an organism and its environment Thermoregulation • Temperature affects enzyme activity • Increase of 100C increase rate 2-3 times • Q10 Effect: Q10 is multiple to which reaction rate increases with increase of 100C. • Heat gain must balance heat loss to maintain constant temp. 5 Four methods of heat exchange Infrared Radiation 1. conduction 2. convection 3. radiation 4. evaporation 6 7 Figure 44.3x Heat exchange Ectotherm • Low metabolism • Heat from metabolism too small to affect body temp. • Temp determined by surroundings • Behavioral adaptations. Figure 44.4 The relationship between body temperature and ambient 8 (environmental) temperature in an ectotherm and an endotherm Endotherms • Maint temperature > surroundings (usually) • High metabolic rate • Vigorous activity over long period of time. • Stable temperature on land • Energy cost, need more food Humans: 36.5 kcal/kg/day; Mouse: 438 kcal/kg/day; Snake: 5.5 kcal/kg/day 9 Figure 44.5 Countercurrent heat exchangers Thermoregulation 1. Adjust rate of heat exchange between organism and surroundings • Insulation: hair, feather, fat • Vasodilation/vasoconstriction • Countercurrent exchange o Bird, fish, wolf leg o Wolf leg foot pad just above 00C, minimizes heat loss 1 0 Countercurrent Heat Exchange 1 Figure 44.6 Skin as an organ of thermoregulation 2. Evaporative cooling 1 • Sweat, breathe, panting, bathing 1 Figure 44.6x Skin, cross section 2 1 Figure 44.x1 Harbor seal 3. Behavioral Responses 3 • Activity level: humans cool down after activity • Bask in sun • Swim • Move to shade • **both ectotherms AND endotherms do this. 1 Figure 44.7x Behavioral adaptation for thermoregulation 4. Change rate of metabolic heat production (endotherms) 4 1 Thermoregulation in Mammals Narrow range 5 and Birds • Mammals: 36-380C • High Metabolic rate 0 • Mitochondria produce heat instead of ATP • Birds: 39-42 C – Nonshivering thermogenesis-throughout body – Brown Fat (Neck)—heat production • Shivering Counteract constant heat loss •Insulation • Vasodilation/Vasoconstriction •Fat/Blubber • Evaporative Cooling • Sweat • Panting 1 6 Thermoregulation in Amphibians and Reptiles • Ectotherm • Low metabolic rates have little influence on Body Temp • Behavioral adaptations • Physiological adaptations – Vasoconstrict/dilate to superficial blood vessels • Female Python—endothermic when incubate eggs--shivering 1 Figure 44.8 Thermoregulation in large, active fishes Fishes 7 • Conform to about 1-20 of surroundings • Lose heat at gills • Countercurrent exchange 1 Flight muscles generate heat, shiver 8 Flying Insects Figure 44.10 The thermostat function of the hypothalamus and feedback mechanisms 1 in human thermoregulation Regulation in Humans 9 • Hypothalamus = thermostat • Sensors in skin, HT, other regions • Cold Æ vasoconstriction, erect fur, generate heat • Heat Æ vasodilate, sweat, pant Acclimatization • Adjust to tolerate changing temperatures • Biochemical, physiological • Examples o Insulation—thicker coat in winter o Metabolic heat production o Increase production of certain enzymes that will be more active at given temp (fishes) o Change ratio of sat/unsat FA in membrane o Antifreeze compounds (frog) 2 0 Wood Frog (Rana sylvatica) Biology of Cryogenics. Waking from a Dead Sleep Discover, February 2005 2 Wood Frog Liver Cells 1 •Frog Frozen to 250F while alive •Pockets of water (w) remain inside the cell. •High [glc] keep from turning to ice. •Liver cell from frog cooled to -40C (too cold for glucose to protect). •Will not survive thawing. Biology of Cryogenics. Waking from a Dead Sleep Discover, February 2005 Figure 44.11 Body temperature and metabolism during hibernation of Belding’s 2 ground squirrel Torpor: conserve energy during environmental extremes 2 • Hibernation o Winter, long term o Decrease body temp, decrease food need o Save energy o Belding squirrell: 150Cal/day Æ 5-8 Cal/day 2 Estivation Estivation 3 • Summer torpor • Slow metabolism, inactive • Salamander • Lung fish • African Lungfish – Seal inside cocoon o South American/African: only lungs (lose gills at birth) – air tube from fish mouth to exterior o Australian: both lung and gills, use lungs if no water. – Ventilation of Lungs – Survive dry season. 2 Daily Torpor 4 Daily Torpor • Allow body temp to decrease during period of non feeding and inactivity. • Small endotherms with high rate of metabolism • Decrease in metabolism and temperature • Hummingbird – temp drops from 40oC(day) to 13oC(night) •small mammals • Humans—evolutionary remnant 2 Figure 44.12 Salt-excreting glands in birds Water Balance and Waste Disposal 5 • Osmoregulation: controlled movement of solutes between internal fluid and external environment. • Monitor/control composition of bloodÆaffects IF and cells • Salt Balance o Albatross drinks sea water, actively transports salt out of blood Æ tubule Æ nasal gland. • Transport Epithelia o Layer of specialized cells o Move specific solutes in controlled amounts in particular directions. 2 Figure 44.13 Nitrogenous wastes Nitrogenous Wastes 6 • Product of breakdown of proteins and nucleic acids • Type of waste excreted depends on habitat and characteristics of species. Ammonia • Toxic, soluble, tolerate at low concentrations. • Must be excreted with lots of water • Aquatic animals • Benefit: least amount of energy to produce • No land animals b/c toxic and would cause too much water loss Urea • Mammals, adult amphibians, marine fish, turtles • Liver: NH3 + CO2 Æ urea to be excreted by kidney • Less toxic (100,000x less toxic) • Safe transport, store at high concentrations. • Benefit: less water loss to excrete • Cost: energy to produce. Uric Acid • Snails, insects, reptiles, birds • Non toxic • Insoluble in water, paste • Benefit: conserve water • Cost: more Energy to produce Mode of reproduction affects excretion • Egg w/o shell: soluble waste (NH4, urea) b/c diffuse out. • Egg w/ shell: not permeable to liquid, uric acid will not poison embryo, can be stored. 2 Figure 44.14a Osmoregulation in a saltwater fish Water/solute balance in freshwater and marine fish 7 Marine • Hyperosmotic environment • Loss of water by osmosis (skin, gills), replenish by drink/food • Ions/salt accumulate, must actively discharge. o At gills, Cl- actively pumped out, Na+ follows 2 Figure 44.14b Osmoregulation in a freshwater fish Freshwater 8 • Hypoosmotic environment • Water diffuses in, salts diffuse out. • Must obtain salt from food • Must excrete large amounts of dilute urine. Salmon • Change mode of excretion when migrate. • Ocean: drink water, salt out gills • Freshwater: do not drink, dilute urine, gills take in salt 2 Figure 44.16 Water balance in two terrestrial mammals Land animals 9 • Kangaroo Rat o recovers 90% of water from metabolism (respiration) o 10% of water from seeds. o Lose water mainly to evaporation during gas exchange. • Human loses water mainly to urine 3 Figure 44.17 Key functions of excretory systems: an overview Excretory System 0 • Regulate solute movement internal/external • Refine filtrate Æ urine 1. Filtration • Non selective • Driven by pressure • Water, small solutes • Recover water and solutes 2. Reabsorption • Valuble solutes—glucose, salt, amino acids 3. Secretion: toxins, ionsÆtubule 4. Excretion Compare to cleaning house: make pile of all extra junk, sift through and pick out things to keep, get rid of stuff don’t need. 3 Figure 44.18 Protonephridia: the flame-bulb system of a planarian Excretory system has two functions 1 • Excretory: N waste out • Osmoregulatory: water and salt balance Water potential has huge role in process. Protonephridia • Flatworms • Dead end tubule, lack internal opening • Branch in body • Flame bulb: cap, single cell • Beat cilia: draw water/solutes in • Reabsorb most of solute Æ dilute urine • Mainly osmoregulation (water and salt) • Not excretory—N-waste out through body surface and GV 3 Figure 44.19 Metanephridia of an earthworm Metanephridia 2 • Annelids (2 per segment) • Internal opening—nephrostome • Nephrostome: ciliated funnel, collect fluid. • Excretory and osmoregulatory • Reabsorb salts through capillaries • Dilute urine Æ balance osmotic water intake. • Out a nephrostome. 3 Figure 44.20 Malpighian tubules of insects Malphigian Tubules 3 • Insects, terrestrial arthropods • Excretory and osmoregulatory • Dead end in hemolymph, open to digestive tract. • Nitrogeneous waste secreted into tubule, water follow by osmosis. • To rectum • Reabsorb water at rectum • Waste Æ feces 3 Figure 44.21 The human excretory system at four size scales Vertebrate Kidney 4 • Osmoregulatory and excretory • Bean shape, 10cm long, 1 pair • <1% of body weight, receive 20% cardiac output. • Renal Artery/Renal Vein • Cortex (outer), Medulla (Inner) Nephron = functional unit • 1,000,000 per kidney (80km) Glomerulus/Bowman’s Capsule/Tubule 1100-2000L blood in to kidney per day Æ 180L filtrate Æ 1.5L urine Filtration • BP forces fluid through glomerulus into