Chapter 44 Regulating The Internal Environment

1. Chapter 44Regulating The Internal Environment

2. Key Words • Homeostasis- An animals ability to regulate their internal environment • Thermoregulation- how animals maintain internal temperature within a tolerable range • Osmoregulation- how animals regulate solute balance and loss of water • Excretion- how animals get rid of nitrogen-contained waste

3. Let’s take a closer look thermoregulation…… • Thermo(heat)-Regulation(control) There are four physical processes for heat gain and loss: Conduction Convection Radiation Evaporation

4. Endotherms vs. Ectotherms Ectotherms- low metabolic rate therefore it conforms to it’s surroundings -More likely to survive Endotherms- have a high metabolic rate to maintain body temperature -More advantageous

5. What Helps Animals Thermoregulate? • Adjusting the rate of heat exchange between the animal and it’s environment -Vasodilation: an increase in the diameter of blood vessels which ultimately relax muscles of the vessel walls -Vasoconstriction: Reduces blood flow and heat transfer by decreasing the diameter of vessels

6. Continued…. -Counter Heat Exchanger: Special arrangement of vessels that traps heat in the body core . *reduces heat loss in endotherms

7. Continued… 2. Cooling by evaporative heat loss 3. Behavioral aspects 4. Changing the rate of metabolic heat production

8. Closer look at endothermy… • Mammals & Birds • 36-42 °C • In order to maintain a body temperatures…. High Metabolic Rate(moving , SHIVERING!) Insulation Vasodilation Vasoconstriction Blubber Evaporative cooling

9. Closer look at ectothermy… • Fishes • - Most heat is lost but some use large arteries • Amphibians & Reptiles • Control body temperatures by behavior • Invertebrates • thermoconformers • Some are Endotherms

10. Feedback Mechanisms in Thermoregulation • Hypothalamus (Ch 48)- Never cells that control thermoregulation, located in brain

11. Adjusting to Changing Temperatures • Acclimatization- Animals that can adjust to a new range of environmental temperatures over a period of days/weeks • Both endotherms and ectotherms • Even cells do this

12. Environmental Extremes? • Torpor: a physiological state in which activity is low and metabolism decreases • Hibernation • Estivation • Daily torpor

13. Water Balance and Waste Disposal REFRESHER! • Osmoregulation- how animals regulate solute balance and loss of water PAGE 937

14. Production of Urine • Two step Process • 1.) body fluid such as blood is collected and is adjusted by the secretion of solutes in order to balance vitamins and minerals in the blood • 2.) Then the fluid is filtrated through a selectively permeable membrane • The end product is known as the filtrate

15. Evolutionary History of Insects • Malphigian tubules are the organs that remove nitrogenous wastes and function in osmoregulation • Similar to humans, Insects need certain solutes to function so the tubules also control the release of the solutes • Mechanism allows for greater water conservation

16. Earthworms (annelids) • excretory organ opens to coelom • each segment of a worm has a pair of nephridia • dilute urine • blue segments are the Nephridia that collect the body fluid • Reabsorption of solutes before the blood reaches the collecting tubule

17. Pathway of the Filtrate • Filtration occurs • Reabsorption follows with solutes returning to the blood • Secretion takes apart any nitrogenous wastes and toxins and adds it to the collecting tube • Excretion of the urine occurs where the waste exits through the ureter

18. After the heart receives deoxygenated blood from the posterior vena cava, the inferior vena cava pumps oxygenated blood directly to the kidneys • Then the kidneys remove byproducts such as ammonium and urea as the blood is flowing through

19. The Kidney • Made up of two main regions: • Renal cortex: Contains tubules with blood vessels that transport the blood through. This is where “ultrafiltration occurs • Renal Medulla: contains the structures of the nephrons responsible for maintaining the salt and water balance of the blood( lined with sodium so water is pulled out of filtrate) and further transports the filtrate.

20. Nephron • Main functional unit • Classes of nephrons: cortical nephrons (About 80% and located in Renal Cortex) and juxtamedullary nephrons( Other 20% and located in Renal Medulla) • Made up of glomerulus that starts the filtering of the blood • Moves to the bowman’s capsule, which collects the filtrate

21. Nephron Functions • Regulates blood pressure: When blood pressure drops, the distal tubule releases less sodium then normal. Then the juxtamedullary cells release an enzyme called renin which causes the blood vessels to constrict and thus increasing blood pressure. • Controls Electrolyte levels: Hormones are stimulated by the nephron when levels of certain solutes such as Ca and Na drop to unsafe levels. These hormones include aldosterone and angiotensin II • Regulates blood PH: If the pH level drops below a certain level ( normal being around 7.3) more Hydrogen ions are secreted and if the pH level increases then less ions are secreted.

22. Loop of Henle • From the Bowman’s capsule the filtrate moves to the loop of henle • The loop of Henle continues the transport of the filtrate into the descending limb of the loop and also assists in the reabsorption of water out of the tubules. This increases the concentrations of the solutes • Then the filtrate is transported through the ascending limb where the solutes diffuses out of the tubules since they are permeable to salts but not water • Other solutes such as K+ and NaCl are regulated as the filtrate passes through the Distal Tubule • Then the filtrate is transported to the collecting duct where the duct becomes permeable to urea (waste product from breakdown of proteins) and then is expelled

24. Interesting Facts • About 2,000 L of blood flows through a pair of kidneys each day • 99% of the water and other sugars are reabsorbed back into blood • Leaves about 1.5L of Urine that we pee out everyday