Regulating the Internal Environment: Thermoregulation & Osmoregulation

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

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

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

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.

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

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, some bony fish. Less toxic. Produced in liver by combining ammonia with CO2 then transported to kidneys.

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.

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) youtube link Kidneys ~ vertebrates

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%)

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

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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

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