Chapter 25- Control of Internal Environment

• Ammonia• Bowman’s capsule• Collecting duct• Countercurrent heat exchanger• Dialysis• Distal tubule• Endotherms• Estivation• Excretion• Excretion• Exotherms• Filtrate• Filtration• Glomerulus• Hepatic portal vessel• Hibernation• Loop of Henle• Nephrons

• Osmoconformers• Osmoregulation• Osmoregulators• Proximal tubule• Reabsorption• Renal cortex• Renal medulla• Secretion• Thermoregulation• Torpor• Urea• Ureter• Urethra• Uric acid• Urinary bladder

Thermoregulation • Maintenance of internal temperature

– Endotherm- organisms that derive body heat from metabolism– Ectotherm- absorb most heat from their surrounding

• 4 ways heat is gained/lost:– Conduction- direct transfer of heat through contact– Convection- transfer by movement of air or water past a body

surface– Radiation- emission of electromagnetic E – Evaporative cooling- loss of heat from surface of a liquid that is

transforming into gas

Maintaining Body Temperature• Change rate of heat

lost/gained by the 4 methods on previous slide

• Countercurrent heat exchanger- prevents heat loss, like it does to prevent O2 loss in fish

• Behavior affects body temperature – Ex: migrate, bask in

sun, huddling together

Maintaining Body Temperature

• Alter metabolic rate of heat production• Reducing metabolic rate- saves E

– Torpor- state of reduced activity, body temp and metabolic rate decrease, heart and respiratory system slows

– Hibernation- long term torpor- live off E stored in body fat– Estivation- “summer torpor”- to survive long periods of high temp

with little food or water

Osmoregulation

• Osmoconformers- aquatic animals that have solute conc. in body fluids = to seawater– * will need to expend E to keep ion conc’s maintained

• Osmoregulators- animals whose conc of solute is different from environment, they expend E to control water gain/loss– saltwater vs. freshwater fish

• Sweating- produces water loss, while trying to stay cool (thermoregulation)

Osmoregulation in fish

Waste disposal

• Animals need to dispose of nitrogen wastes (from protein and nucleic acid breakdown) or be at risk of poisoning– Aquatic animals- can dispose of ammonia because

it’s very soluble in water, it readily diffuses into water environment

– Most terrestrial animals- (ammonia can’t diffuse into air) body expends E to convert ammonia into less toxic urea/uric acid and is then released through excretory system

Carbs and fats- broken down into carbon dioxide and water

Human Excretory System

Parts of the excretory system• Ureter- tube that leads to urinary bladder- where urine is

stored until it is expelled through urethra• Kidney- regulates chemical composition in blood,

therefore chem composition of body fluids– Renal cortex, renal medulla, renal pelvis– Produces 180L of filtrate a day which is refined to produce 1.5L

of urine!!– Nephron- extract filtrate and refine it, 1 million per kidney

• Bowman’s capsule- receiving end, around glomerulus, absorption takes place here

• Glomerulus- ball of capillaries in capsule, together they make up blood filtering unit

• Proximal tube, loop of Henle and distal tube- refine filtrate

4 functions of the Excretory System

• Filtration- water & molecules forces through capillary wall and enter nephron

• Reabsorption- water & valuable solutes (glucose, aa’s, salts)- reclaimed from filtrate and return to blood

• Secretion- certain molecules are moved to filtrate from blood– Ex: excess K+ and H+ (keeps blood from becoming acidic)

• Excretion- urine passes from kidney through ureters to bladder

– Gradient changes from cortex to inner medulla, helps with water absorption

– Drugs that were processed in liver enter filtrate in proximal tubule

– ADH (antidiuretic hormone)- signals nephron to reabsorb water

• Alcohol inhibits ADH = excessive urination

Dialysis • Does the job of kidney,

cleanses blood– Timely and costly

unfortunately

The Liver

• More functions than any other organ!!!– Aids in digestion- produces bile– Prepares nitrogen wastes- synthesizes urea– Synthesizes plasma proteins- blood clotting– Regulates blood glucose- converts glucose to glycogen and

stores it for later– Helps kidneys get rid of alcohol/drugs- converts them into

inactive products that kidneys can remove– Hepatic portal vessel- conveys blood to liver to modify/detox –

absorbs substances before blood is pumped to body

How the human kidney concentrates urine