1. Chapter 44 ~ Regulating the Internal Environment

2. Homeostasis: regulation of internal environment Thermoregulation internal temperature Osmoregulation solute and water balance Excretion nitrogen containing waste

3. Regulator vs Conformer Regulator – moderates internal change is spite of environmental change (homeostasis) Conformer – allow some internal conditions to vary with environmental change

4. Energy and Materials Budget

5. Thermoregulation – balancing heat gained with heat lost Temperature can have an impact on the following: –Enzymes – work in a certain temperature range Q 10 – the factor that enzyme rate increases with an increase of 10 degrees C –Membrane fluidity – temp. affects the fluidity of membranes Lower temp. – organism needs to increase fluidity

6. Calculating Q 10 Rate of enzyme at T + 10C/rate of enzyme at T

7. Types of Heat Transfer 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

8. Ectothermic vs Endothermic Low metabolic rate Generates minimal heat internally Less energy requirements High metabolic rate Heat generated internally can heat the body Requires more energy to generate this heat

10. Adaptations for heat regulation Insulation – fat, hair, feathers Circulation – –Vasodilation – blood vessels dilate (relax), blood flow increases, heat transfer increases –Vasoconstriction – blood vessels contract, blood flow decreases, heat transfer decreases –Countercurrent exchange – reduces heat loss

11. Countercurrent exchange

12. Adaptations (cont.) Evaporative cooling – sweating, panting Behavior –Basking in sun/cooling in shade –Migration –Hibernation Changing metabolic rate (heat production)

13. Increasing heat production (metabolic rate) - endotherms Endotherms must counteract their heat loss to the environment Muscle activity – moving, shivering Nonshivering thermogenesis (NST) – hormones released in the body can cause mitochondria to increase activity and release heat Brown fat – Tissue that can generate heat at a high rate

14. Feedback mechanisms

15. Regulation during environmental extremes – extreme hot or cold, no food available 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

16. Ground Squirrels

17. 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 NH 3 and CO 2 ) Uric acid: birds, insects, many reptiles, land snails

18. 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

19. Excretory Systems Production of urine by 2 steps: Filtration (nonselective) Reabsorption (secretion of solutes) Protonephridia ~ flatworms (“flame-bulb” systems) Metanephridia ~ annelids (ciliated funnel system) Metanephridia ~ annelids (ciliated funnel system) Malpighian tubules ~ insects (tubes in digestive tract) Malpighian tubules ~ insects (tubes in digestive tract) Kidneys ~ vertebrates

20. 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 Cortical nephrons (cortex; 80%) Juxtamedullary nephrons (medulla; 20%)

21. 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

22. Basic Nephron Function

23. Nephron Function, I Proximal tubule: secretion and reabsorption

24. Nephron Function, II Loop of Henle: reabsorption of water and salt Distal tubule: secretion and reabsorption

25. Nephron Function, III Collecting duct: reabsorbs water, salt, some urea

26. 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 angiotension (plasma protein) to angiotension II (peptide); increase blood pressure and blood volume by constricting capillaries Angiotension 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

27. Hormonal Control