the internal environment maintaining internal balance internal environment maintained in narrow...
TRANSCRIPT
Chapter 42The Internal Environment
Maintaining Internal BalanceInternal environment maintained in narrow range
HomeostasisExtracellular fluid
Interstitial—between cells of body tissuesBloodStays stable because of exchanges substances w/
environmentFluids & solutes enter by osmosis, digestive
system, metabolismMinerals & water lost through respiratory
system, skin, kidneys
OsmosisDiffusion—movement of substance
from high to low concentrationOsmosis—diffusion of water
across a selectively permeable membraneIsotonic solution—concentration
of solutes equal in and out of cell, no net movement of water
Hypertonic solution—concentration of solutes greater outside of cell than inside; water moves out of cell
Hypotonic—concentration of solutes greater inside of cell than outside; water moves into cell
Aquatic AnimalsMollusks, arthropods,
cartilaginous fishBody fluids nearly
isotonic to seawaterNo movement of salt
or waterNo difficulty
maintaining salt/water balance
Aquatic AnimalsMarine bony fish
Seawater is hypertonicProne to water lossDrink seawater constantly
to take in enough waterExcess salt excreted by
gillsScant, highly concentrated
urine retains water
Aquatic AnimalsFreshwater bony fish
Freshwater is hypotonicProne to water gainNever drink waterProduce large amount of
dilute urineMust actively take salt
through gills and food
Land AnimalsBigger risk of dehydration since not
surrounded by waterWater gain—food, drink, metabolic reactionsWater loss
Do not loose through osmosisUrinary excretionEvaporation from respiratory surfacesSweating in mammals
Land AnimalsBalance
Birds & reptiles have glands to eliminate salt Marine iguanas specialized
Reptiles dry, scaly skin to prevent water loss
Desert mammals (camel, kangaroo rat, etc.) Reabsorb moisture from exhaled air Limited amount of urine, highly
concentrated No sweat glands More absorption of water from
feces More active in cooler parts of day
Nitrogen WasteProduced by breakdown of nucleic acids &
amino acidsIngestionMetabolic processes
Ammonia producedVery toxic Must be eliminated
Nitrogen WasteAquatic animals
Excrete ammonia directly in urineNeed large amounts of water
Insects, reptiles, birdsExcrete uric acidLow toxicityPoorly soluble in water
Therefore highly concentrated Large amount of water conserved
Mammals, terrestrial amphibiansExcrete ureaLess toxic than ammoniaExcreted in moderately concentrated solution
Excretory OrgansFlame cell
Nematodes, platyhelminthes, flatworms, rotifers
Cilia in cells move water through
Tubules remove excess water
Excretory OrgansNephridium
Many invertebrates, mostly annelids
Cilliated cells move fluid from coelom into nephridium
Capillaries around tubule reabsorbs solutes
Dilute urine expelled through external pore
Excretory OrgansMalpighian tubules
Insects, myriapods, arachnids
Absorb water, solutes, wastes from surrounding hemolymph
Wastes excreted through gut
Amount of fluid absorbed dependent on environment
Excretory OrgansKidney
Most vertebratesFilter blood Produce urine
Urea & uric acidOften other functions
Regulate blood pressure Glucose metabolism RBC production
Urinary SystemKidneys
PairedCortexMedullaPelvis
Only found in mammals
Urinary SystemUreter—kidney to bladderBladder—urine storage
Only in mammalsUrethra—bladder to
outsidePart of reproductive tract
in malesSeparate in females
NephronFunctional unit of
kidneyRenal Corpuscle
Non-selective filtration
Glomerulus Blood vessels enter
kidneyGlomerular
capsule Filtrate collected
NephronRenal Tubules
99% of filtered products reabsorbed
Proximal convoluted tubule Organic Solutes (amino acids,
glucose) 2/3 of salt & water
Loop of Henle Concentrates salt (absorbs
water)Distal convoluted tubule
Reabsorb calcium, excrete potassium
Nephron1 million nephrons in human kidney25% must be functional for homeostasis
Maintain blood pHRelease erythropoeitin for RBC productionStimulate ADH release when dehydratedMaintain blood pressure
Chronic renal failure irreversibleDialysis—pump blood through machine that
allows diffusion of wastes, then pump blood back into body
Temperature RegulationHeat gain & loss
Thermal radiation Sun, warm object Warmth produced by
metabolismConduction
Transferred between two objects in direct contact
Convection Moving air or water “Wind chill”
Evaporation Water on surface converts to
gas Draws heat from body
Temperature RegulationHeat stress
Peripheral vasodilation—diameter of skin blood vessels increases
Evaporation Sweat—most mammals, no other
animals Licking fur Panting
Move to shaded, cooled area Under surface of ground, rocks
Design adaptations Desert animals usually smaller
(greater surface area per body size), less body fat, thinner hair coats
Temperature RegulationCold stress
Peripheral vasoconstrictionPilomotor response—hairs stand up
Layer of still air next to skin Reduce convective and radiative heat
lossShivering
Muscles contract 10-20x per second Generates internal heat
Nonshivering heat production Long-term (hibernating animals) Brown adipose tissue
Move to warmer area Reptile basking
Design adaptations Thicker coat, larger size (smaller surface
area), increased fat for insulation