Presentation on theme: "Homeostasis - maintenance of relatively constant internal environment"— Presentation transcript:
1Homeostasis - maintenance of relatively constant internal environment Body temperature
2Endotherms Mammals and birds generally maintain body temperatures within a narrow range that is usually considerably warmer than the environment oC for most mammals and 39-42oC for most birds.Ectotherms Amphibians, reptiles control body temperature mainly by behavior.
3Thermoregulate Adjusting the rate of heat exchange between the animal and its surroundings. InsulationBlood flow - Vasodilation vs.Vasoconstriction
4Thermoconformersuse countercurrent heat exchangersto trap heat in the muscles, digestive tract, eyes, or brain.
5Homeostasis - Osmotic water/salt balance & waste Osmoregulation - water salt balancesalt-excreting glands remove excess sodium chloride from the bloodgills of freshwater fishes actively pump salts from the dilute waterTransport epithelia in excretory organsmaintain water balance anddisposing of metabolic wastes.
6Nitrogenous WastesIn fishes, most of the ammonia is lost as ammonium ions (NH4+) at the gill epithelium
7Mammals, most adult amphibians, and many marine fishes and turtles excrete mainly urea. Urea is synthesized in the liver by combining ammonia with carbon dioxide and excreted by the kidneys.Advantages -Urea requires less water loss100,000 times less toxicthan that of ammonia.Disadvantage -must expend energy toproduce it from ammonia.Amphibians excrete ammoniawhen they are aquatic tadpoles,switch to urea when they areland-dwelling adults.
8Land snails, insects, birds, and many reptiles excrete uric acid as the main nitrogenous waste. Advantages:Uric acid is relatively nontoxiclargely insoluble in waterexcreted as a semisolid pastewith very small water loss.Disadvantage:More energetically expensiveto produce than urea
9Adaptations for excreting nitrogenous wastes - 1. Mode of reproductionSoluble wastes can diffuse out of a shell-less amphibian egg (ammonia)carried away by the mother’s blood in a mammalian embryo (urea).Shelled eggs of birds and reptiles are not permeable to liquidsIn these animals, uric acid precipitates out of solution and can be stored as a solid within the egg (allantois) and left behind when the animal hatches.2. Habitat.Terrestrial turtles - excrete mainly uric acidAquatic turtles excrete both urea and ammonia.
10Osmoregulation - balance between osmotic gain and loss of water Animal cells - lack cell wallsswell and burst if there is a continuous net uptake of watershrivel and die if there is a substantial net loss of water.Osmosis occurs whenever two solutions separated by a membrane differ in osmotic pressure, or osmolarity (moles of solute per liter of solution).Isotonic (isoosmotic)HypertonicHypotonicOsmoregulators expend energy to control their internal osmolarityOsmoconformers -isoosmotic with their surroundingsMost marine invertebrates (jellyfish) are osmoconformers-osmolarity same as seawater.
11An osmoregulator must discharge excess water if it lives in a hypoosmotic environment (freshwater) freshwater animals are constantly gaining water by osmosis and losing salts by diffusion.Freshwater protists such as Amoeba and Paramecium have contractile vacuoles that pump out excess water.Many freshwater animals, including fishes, maintain water balance by excreting large amounts of very dilute urine, regaining lost salts in food, and by active uptake of salts from their surroundings.
12OsmoregulatorTake in water to offset osmotic loss if it inhabits a hyperosmotic environment (terrestrial habitats).Marine animals can maintain internal osmolarities different from that of seawater.Marine fishes lose waterthrough their skin and gills.To balance this drink large amounts of seawater and they excrete ions by active transport out of the gills.
13Marine sharks and most other cartilaginous fishes use a different osmoregulatory “strategy.” Salts diffuse into the body from seawater and are removed by the kidneys, a special organ called the rectal gland, or in feces.Unlike bony fishes, marine sharks do not experience a continuous osmotic loss because high concentrations of urea in body fluids lead to an osmolarity slightly higher than seawater, water slowly enters the shark’s body by osmosis and in food, and is removed in urine.
14Adaptations that reduce water loss are key to survival on land. Terrestrial animals have body coverings that help prevent dehydration Waxy layers in insect exoskeletonsMultiple layers of dead, keratinized skin cells.Humans die if they lose about 12% of their body water
15Most excretory systems produce a filtrate by pressure-filtering body fluids into tubules.
16Flatworms have an excretory system called protonephridia, consisting of a branching network of dead-end tubules.These are capped by a flame bulb with a tuft of cilia that draws water and solutes from the interstitial fluid, through the flame bulb, and into the tubule system.
17Metanephridia, another tubular excretory system, consist of internal openings that collect body fluids from the coelom through a ciliated funnel, the nephrostome, and release the fluid through the nephridiopore.Found in most annelids, each segment of a worm has a pair of metanephridia.
18Insects and other terrestrial arthropods have organs called Malpighian tubules that remove nitrogenous wastes and also function in osmoregulation.These open into the digestive system and dead-end at tips that are immersed in the hemolymph.
20Filtrate from Bowman’s capsule flows through the nephron and collecting ducts as it becomes urine
21Proximal tubuleSecretion and reabsorption in the proximal tubule substantially alter the volume and composition of filtratereabsorption of most of the NaCl and waterDescending limbAscending limbpermeable to salt not waterDistal tubuleHormonal control of reabsorptioncontributes to pH regulationsecretion of H+and reabsorptionof bicarbonate (HCO3-).Collecting duct
22Mammalian Kidneycounter-current multiplier between the ascending and descending limbs of the loop of Henledesert mammals, have exceptionally long loops of Henle.
23Antidiuretic hormone (ADH). ADH produced in hypothalamus of the brainand stored in and released from the pituitary glandOsmoreceptor cells in the hypothalamus monitor the osmolarity of the blood.
24juxtaglomerular apparatus (JGA), Releases renin when there’s a decrease in blood pressure or blood volume in the afferent arteriole