Regulating the Internal Environment:

1. Regulating the Internal Environment: • Thermoregulation & Osmoregulation

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

3. Regulation of body temperature • Thermoregulation • 4 physical processes: • 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 (electromagnetic waves) Not transferred by molecules. • Evaporation~loss of heat from liquid to gas • Sources of body heat: • Ectothermic: determined by environment • Endothermic: high metabolic rate generates high body heat

4. Regulation during environmental extremes • Torpor~ low activity; decrease in metabolic rate. • 2 types: • Hibernation-long term or winter torpor (winter cold and food scarcity); bears, squirrels • Estivation- short term or summer torpor (high temperatures and water scarcity); fish, amphibians, reptiles • Both often triggered by length of daylight

5. Thermoregulation amongst the Phyla…. • Invertebrates: most have no direct control over body temperature (complete ectotherms) • May orient body to maximize or minimize heat from the sun. • Some flying insects can generate internal heat by contracting flight muscles in synchrony. • Social insects can use interaction between each other…. • Huddle to stay warm; fan each other to cool • Reptiles/Amphibians: most are generally ectothermic. • Again, seek warmer or cooler “microenvironments” to adjust temperatures. • Some reptiles can use vasoconstriction to minimize heat loss or shiver to generate a few extra degrees of heat.

6. Still amongst the phyla….. • Fish: again, generally ectothermic. • Some are partial endotherms: • (tuna, swordfish, sharks) • Heat production in swimming muscles, combined with countercurrent circulation can raise the temperature of the body core. • Mammals/Birds: true endotherms • Maintain relatively high temperature over a very narrow range. • 36o –38o C for Mammals • 40o-42oC for Birds • Warming Mechanisms: • Shivering • Vasoconstriction centralizes warmth • Fat burning. • Cooling Mechanisms: • Vasodilatation dissipates heat • Sweating increases evaporative cooling

7. 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; • It’s all about “Deamination” resulting in: • Ammonia: most aquatic animals, many fish Diffuses easily out of soft body surfaces • Uric acid: birds, insects, many reptiles. • Much less soluble than ammonia • Eliminated as a paste through “cloacae”. • Allows reproduction though shelled eggs because it can precipitate out without becoming toxic. • Urea: mammals, most amphibians, sharks, bony fish. • Less toxic. • Produced in liver by combining ammonia with CO2 then transported to kidneys.

8. Water Balance • Osmoconformer: no active adjustment of internal osmolarity. Isoosmotic to environment. Most marine animals. • Osmoregulator: adjust internal osmolarity (freshwater, marine, terrestrial). • Freshwater fishes(hyperosmotic)- gains water, excretes large amounts of urine. Salt replenished by consuming high salt content foods or actively transporting ions. • Marine fishes(hypoosmotic)- loses water, gains salt; drinks large amount of saltwater secrete very little urine. • Anhydrobiosis-dehydrated animals. Often have “trehalose”- a disaccharide that replaces water around membranes and proteins.

9. Excretory Systems • Production of urine by 2 steps: • 1.) Filtration (nonselective) 2.) Reabsorption (secretion of solutes) • Protonephridia ~ flatworms (“flame-bulb” systems) weblink • Metanephridia ~ annelids (ciliated funnel system) • Malpighian tubules ~ insects (tubes in digestive tract) http://entochem.tamu.edu/insec • Kidneys ~ vertebrates

10. 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%)

11. 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

12. Basic Nephron Function • D:\bc_campbell_biology_7\0,7052,3117252-,00.html

13. 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) ~ when blood volume/pressure is low it secretes enzyme renin which increases blood pressure/volume by constricting capillaries; initiates conversion of angiotensinogen (plasma protein) to angiotensin II (peptide). • Angiotensin II also stimulates adrenal glands to secrete aldosterone; acts on distal tubules to reabsorb more sodium, thereby increasing blood pressure (renin-angiotensin-aldosterone system; RAAS) • Atrial Natriuretic Factor (ANF) ~ walls of atria; inhibits release of renin, salt reabsorption, and aldosterone release

14. Hormonal Control • D:\bc_campbell_biology_7\0,7052,3117252-,00.html