Presentation on theme: "CONTROLLING THE INTERNAL ENVIRONMENT Volunteer State Community College Nancy G. Morris Campbell: Chapter 44 This presentation will probably involve audience."— Presentation transcript:
CONTROLLING THE INTERNAL ENVIRONMENT Volunteer State Community College Nancy G. Morris Campbell: Chapter 44 This presentation will probably involve audience discussion, which will create action items. Us PowerPoint to keep track of these action items during your presentation In Slide Show, click on the right mouse button Select “Meeting Minder” Select the “Action Items” tab Type in action items as they come up Click OK to dismiss this box This will automatically create an Action Item slide at the end of your presentation with your points entered.
Control the Internal Environment Most animals can survive environmental fluctuations more extreme than any individual cell could tolerate… Most animals can survive environmental fluctuations more extreme than any individual cell could tolerate… because mechanisms of homeostasis maintain internal environments within ranges tolerable to body cells. because mechanisms of homeostasis maintain internal environments within ranges tolerable to body cells.
Mechanisms of homeostasis: Adaptation to the thermal environment: thermoregulation Adaptation to the osmotic environment: osmoregulation Strategies for the elimination of waste products of protein catabolism: excretion
Regulation of Body Temperature Metabolism & membrane properties are very sensitive to changes in an animal’s internal temperature. Each animal lives in, and is adapted to, an optimal temperature range in which it can maintain a constant internal temperature when external temperatures fluctuate. Maintaining the body temperature within a range that permits cells to function efficiently is known as thermoregulation.
4 physical processes account for heat gain or loss: 1) Conduction 2) Convection 3) Radiation 4) Evaporation Evaporation & convection are the most variable causes of heat loss.
4 physical processes account for heat gain or loss: Conduction is the direct transfer of heat (thermal motion) between molecules of the environment & body surface. –Heat is always conducted from a body of higher temperature to one of lower temperature. –Water is 50 to 100 times more efficient than air in conducting heat. –On a hot day, an animal in cold water cools more rapidly than one on land.
4 physical processes account for heat gain or loss: Convection is the transfer of heat by movement of air or liquid past a body surface. –For example, breezes contribute to heat loss from an animal with dry skin.
4 physical processes account for heat gain or loss: Radiation is the emission of electromagnetic waves produced by all objects warmer than absolute zero. –It can transfer heat between objects not in direct contact. –For example, an animal can be warmed by the heat radiating from the sun.
4 physical processes account for heat gain or loss: Evaporation is the loss of heat from a liquid’s surface that is losing some molecules as gas. -Production of sweat greatly increases evaporative cooling -Can only occur if surrounding air is not saturated with water molecules.
Major source of heat? Ectotherms derive body heat mainly from their surroundings –Invertebrates, fishes, reptiles, amphibians Endotherms derive heat mainly from metabolic activity –Mammals, birds, some fishes, numerous insects
Thermoregulation: Involves physiological and behavioral adjustments. Heat loss is reduced by presence of hair, feathers, and fat just below the skin. The amount of blood flowing to the skin can be changed to regulate heat exchange: vasodilation and vasoconstriction. Evaporative heat loss: panting, sweating, bathing increases evaporative cooling across the skin.
Behavioral Responses In winter, many animals bask in the sun or on warm rocks. In summer, many animals burrow or move to damp areas. Some animals migrate to more suitable climates.
Metabolic heat production Occurs only in birds and mammals Increased muscle activity and shivering can greatly increase metabolic heat produced.
Water Balance & Waste Disposal The majority of cell in most animals (all but sponges and cnidarians) are not exposed to the external environment, but are bathed by an extracellular fluid. Animals with an open circulatory system have an extracellular compartment containing hemolymph which bathes the cells. Animals with a closed circulatory system have two extracellular compartments – interstitial fluid and blood plasma.
Nitrogenous Wastes The metabolism of proteins and nucleic acids produces ammonia, a small & very toxic waste product. Some animals excrete the ammonia directly, while other convert it to urea or uric acid, which are less toxic, but require ATP to produce.
Nitrogenous Wastes: Ammonia: water soluble and permeates membranes easily. produced by aquatic animals. In soft-bodied invertebrates, ammonia diffuses across the body surface and into the surrounding water. In fishes, ammonia is excreted as ammonium ions across gill epithelium.
Nitrogenous Wastes: Urea Terrestrial animals can not excrete ammonia because it requires large amounts of water and is so toxic it must be eliminated quickly. Mammals & adult amphibians Can be concentrated because it is 100,000 times LESS toxic than ammonia. Reduces water loss for terrestrial animals. Liver combines CO 2 with amine groups to produce urea. Filtered out by kidneys.
Nitrogenous Wastes: Uric Acid Land snails, insects, birds, and many reptiles. Much less water soluble than urea or ammonia; can be excreted as a precipitate after reabsorption of water from urine. Eliminated through cloaca in paste form (mixed with feces) in birds & reptiles. Because it precipitates out, it can be stored as a solid in the egg without toxic build up.
Osmotic gain and water loss: Animal cells can not survive a net gain or a loss of water. Osmosis – diffusion of water Occurs when two solutions separated by a membrane differ in osmolarity (total solute concentration) In other words, there is a concentration difference.
Osmotic gain & water loss: Recall that when two solutions of differing osmolarities are separated by a semipermeable membrane, water flows from hypo to hyperosmotic.
Osmoregulators expend energy Osmoregulators expend energy to control their internal osmolarity. Water may enter a terrestrial organism through food, drinking, oxidative phosphorylation; water may exit through excretion and evaporation. Aquatic organisms are not affected by evaporation but face a major osmotic problem: water may enter (in fresh water) or leave (in marine water) the body.
Excretion process by which metabolic wastes are eliminated urine, sweat, CO 2, nitrogen are primary wastes 3 excretory functions: –Nitrogen Excretion –Osmotic Regulation –Water Balance
Nitrogen Excretion nitrogenous waste results from deamination of amino acids during protein catabolism packaged as urea by liver filtered out by kidneys
Excretion OSMOTIC REGULATION (regulation of salt, ions, solutes) fluid and electrolyte homeostasis WATER BALANCE (maintenance)
What goes where? Approximately 2,300 mL H 2 O absorbed per day by the small intestine Approximately 300 mL per day lost from the lungs Approximately 1500 mL per day lost from the kidneys Approximately 500 mL per day lost from the skin
Water sources: Principle source is diet. Oxidation of nutrient molecules during aerobic respiration. Why?
Form follows function (again): Excretory structures vary based on the type of osmotic environment in which the animal lives. TERRESTRIAL ANIMALS need to conserve water so … Reptiles & birds excrete nitrogenous wastes as crystalline uric acid. Mammals excrete urea that must be dissolved in water (urine).
Survey of the phyla: PROTONEPHRIDIUM platyhelminthes & nematodes flame-bulb system wastes either diffuse out of body or are excreted into the gastrovascular cavity cilia keeps fluid moving though the tubules
Survey of the phyla: METANEPHRIDIUM annelids coelom is fluid-filled each tubule possesses a nephrostome, collecting tubule, and a nephridiopore nephrostome drains the metamere just anterior to the one in which the metanephridium is located cilia keeps fluid moving though the tubules
Survey of the phyla: Malphigian tubules – arthropods outfoldings of the digestive system. tubules secrete nitrogenous wastes and salts from the hemolymph; water follows the solutes by osmosis. most of the water and salts are reabsorbed across the epithelium in the rectum. dry product called frass is eliminated.
URINE FORMATION: 1) Filtration: Filtrate is forced out of glomerulus & received by Bowman’s capsule. Approximately 180 liters per day or 4.5 x the amount of fluid in the body is forced out into glomerulus. = filters 125 mL per minute
URINE FORMATION: 2) Reabsorption: Occurs simultaneously with secretion. Mostly salts, H 2 O, solutes, vitamins are transported back to peritubular capillaries via active transport. 124 mL of the 125 mL filtered out during filtration will be reabsorbed here.
URINE FORMATION: 3) Secretion: Filtrate is passed through the renal tubule. Walls of the tubule are a single cellular layer of cubodial epithelium specialized for active transport. Molecules remaining in the plasma are selectively removed (penicillin) from the peritubular capillaries & secreted into the filtrate.
URINE FORMATION: Na + Pump – sodium ions are actively pumped across the membrane and Cl - follow passively by electrostatic attraction. Active transport is a “high energy” requirement – higher on a gram for gram basis than the heart beat.
URINE FORMATION: 4) Excretion: Remaining fluids leave the nephron and pass into the renal pelvis (funnel of the ureter) and travel to bladder until released through the urethra.
URINE FORMATION: Normal urine contains: 1) 95% water 2) urea 3) electrolytes – such as –Na +, Cl -, PO 4 -, SO 4 - 4) pigments 5) hormones