CONTROL OF THE INTERNAL ENVIRONMENTChapter 25

THERMOREGULATION Maintenance of an internal temperature

Life processes are temperature sensitive

Stable internal temperature despite external fluctuations

Endotherms use their metabolism Some reptiles, fish, and

insects too Ectotherms gain heat

from external sources Not mutually exclusive

HEAT EXCHANGE Conduction: molecules

between 2 objects in direct contact Higher to lower

temperature movement Convection:

movement of air or liquid past an object

Radiation: electromagnetic waves between 2 objects not in direct contact

Evaporation: surface of a liquid losing molecules as a gas

ADAPTATIONS FOR THERMOREGULATION Metabolic heat

Hormonal boost or moving around to contract skeletal muscles, i.e shivering

Insulation Hair, fur and feathers rise to trap insulating layer of air, goose

bumps are vestigial remnant Blubber in aquatic birds and mammals

Circulatory adaptations Change blood flow by constricting blood vessels to surfaces to

conserve heat, dilation to dissipate Countercurrent heat exchange: adjacent vessels flow

opposite directions Standing on ice, cold water across gills, and muscles

Evaporative cooling Sweating and panting expose moisture to be removed with

heat Behavioral response

Migration, basking in sun when cold and damp areas when hot, bathing, and layered clothing

OSMOREGULATION Balancing uptake and loss of water and solutes

Animal cells: net uptake = ? Net loss = ? Water follows solutes by osmosis

Osmoconformers: no net gain or loss of water Marine invertebrates have body fluids of similar [solute]

as seawater Osmoregulators: necessary to regulate to prevent

changes Freshwater fish have higher [solute] than environment

H2O gained and salt lost = doesn’t drink H20, ions from food, and lots of dilute urine

Saltwater fish have lower [solute] than environment H2O lost and salt gained = drinks salt H2O with salt out gills

and little concentrated urine Land animals obtain H2O from food and drink while losing

water through evaporation and excretion Exoskeleton, dead skin layers, egg shells, and amnitotic sac to

prevent dehydration

DISPOSAL OF WASTES

Metabolism produces toxic nitrogenous wastes that are removed by excretion

Form of waste depends on habitat and evolution

Ammonia too toxic to store, but diffuses in water

Urea less toxic so can be stored, but costs energy and H2O loss to remove

Uric acid insoluble in H2O so is semisolid Costs more energy, but

conserves H2O

URINARY SYSTEM Forms and excretes

urine while regulating water and ion concentrations in body fluids Kidneys filter blood to

extract filtrate which contains H2O, urea, glucose, AA’s, ions, and vitamins

Filtrate is processed so valuable solutes not lost in urine

Blood enters kidney through the renal arteries to be filtered and leaves via the renal veins What is the urine

pathway from kidneys to outside?

THE KIDNEYS Consist of renal cortex

(outer) and renal medulla (inner)

Nephrons are the functional units Start and end in cortex,

part in medulla Bowman’s capsule

encloses the glomerulus which filters the blood Nephron tubule has 3

parts Drains to collecting duct to

join filtrate from other nephrons

Capillary system in Bowman’s capsule and around tubule system

URINARY SYSTEM PROCESSING Filtration

H2O and small molecules through capillary tube from glomerulus to nephron tubule

Reabsorption Filtrate returns valuable solutes to blood (tubule capillaries)

Secretion Excess ions, drugs, and toxic substances from blood

transported into filtrate (tubule capillaries) Excretion

Urine from kidneys to outside

BLO

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FILT

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NaCl enters interstitial fluid, bringing H2O withExcess H+ secreted and HCO3

- reabsorbed to maintain blood pHToxins from liver into tubule systemLoop of Henle facilitates H2O reclaimationADH sets amount of H2O reabsorbtion

Lots of H2O dilutes solutes so ADH down = less H2O retainedAlcohol inhibits ADH release = excess H2O loss