Regulating the Internal Environment (Ch. 44)

Regulating the Internal Environment(Ch. 44)

Conformers vs. Regulators • Two evolutionary paths for organisms

– regulate internal environment• maintain relatively constant internal conditions

– conform to external environment• allow internal conditions to fluctuate along with external

changes

conformer

thermoregulation

regulator

conformer

osmoregulation

regulator

Homeostasis • Keeping the balance

– animal body needs to coordinate many systems all at once

• temperature• blood sugar levels• energy production• water balance & intracellular waste disposal• nutrients• ion balance• cell growth

– maintaining a “steady state” condition

Countercurrent heat exchangersArteries carrying warm blood down the

legs of a goose or the flippers of a dolphinare in close contact with veins conveyingcool blood in the opposite direction, back

toward the trunk of the body. Thisarrangement facilitates heat transfer

from arteries to veins (blackarrows) along the entire length

of the blood vessels.

Near the end of the leg or flipper, wherearterial blood has been cooled to far below the animal’s core temperature, the artery can still transfer heat to the even colder

blood of an adjacent vein. The venous bloodcontinues to absorb heat as it passes warmer

and warmer arterial blood traveling in the opposite direction.

As the venous blood approaches the center of the body, it is almost as warm

as the body core, minimizing the heat lost as a result of supplying blood to body parts

immersed in cold water.

In the flippers of a dolphin, each artery issurrounded by several veins in a

countercurrent arrangement, allowingefficient heat exchange between arterial

and venous blood.

Canadagoose

Artery Vein

35°C

Blood flow

Vein

Artery

30º

20º

10º

33°

27º

18º

9º

Pacific bottlenose dolphin

1

2

3

2

1 3

1

3

2

3

Osmoregulation

Why do all land animals have to conserve water?

always lose water (breathing & waste) may lose life while searching for water

• Water balance – freshwater

• hypotonic• water flow into cells & salt loss

– saltwater• hypertonic• water loss from cells

– land• dry environment• need to conserve water• may also need to conserve salt

hypotonic

hypertonic

Intracellular Waste

• What waste products?– what do we digest our food into…

• carbohydrates = CHO• lipids = CHO• proteins = CHON • nucleic acids = CHOPN

CO2 + H2O

NH2 =

ammonia

CO2 + H2O CO2 + H2O

CO2 + H2O + N

CO2 + H2O + P + N

|

| ||H

HN C–OH

O

R

H–C–

Animalspoison themselves

from the insideby digesting

proteins!

lots!verylittle

Nitrogenous waste disposal• Ammonia (NH3)

– very toxic • carcinogenic

– very soluble• easily crosses membranes

– must dilute it & get rid of it… fast!• How you get rid of nitrogenous wastes depends on

– who you are (evolutionary relationship) – where you live (habitat)

aquatic terrestrial terrestrial egg layer

Aquatic organisms can afford to lose

water - gills Ammonia: most toxic

Terrestrial need to conserve

water Urea: less toxic

Terrestrial egglayers need to conserve

water need to protect

embryo in egg uric acid: least toxic

Nitrogen waste

Mammalian System• Filter solutes out of blood & reabsorb

H2O + desirable solutes• Key functions

– Filtration: fluids (water & solutes) filtered out of blood into glomerulus

– Reabsorption: selectively reabsorb (diffusion) needed water + good solutes back to blood

– Secretion: toxins extracted from body fluids added here!

– Excretion: expel concentrated urine (N waste + solutes + toxins) from body

blood filtrate

concentratedurine

Mammalian Kidney

kidney

bladder

ureter

urethra

renal vein& artery

nephron

epithelialcells

adrenal glandinferior

vena cavaaorta

Nephron Functional units of kidney

1 million nephrons per kidney

Function filter out urea & other

solutes (salt, sugar…) blood plasma filtered

into nephron high pressure flow

selective reabsorption ofvaluable solutes & H2O back into bloodstream greater flexibility & control

“counter current exchange system”

whyselective reabsorption

& not selectivefiltration?

Mammalian kidney

Proximaltubule

Distal tubule

Glomerulus

Collecting ductLoop of Henle

Aminoacids

Glucose

H2O

H2O

H2O

H2O

H2O

H2O

Na+ Cl-

Mg++ Ca++

• Interaction of circulatory & excretory systems

• Circulatory system– glomerulus =

ball of capillaries• Excretory system

– nephron– Bowman’s capsule– loop of Henle

• proximal tubule• descending limb• ascending limb• distal tubule

– collecting duct

Bowman’s capsule

Na+ Cl-

Summary • Not filtered out

– Cells, proteins (antibodies, enzymes) remain in blood, they’re too big

• Reabsorbed: active transport– Na+ Cl-, amino acids, glucose (size)

• Reabsorbed: diffusion– Na+, Cl–, H2O

• Excreted– Urea, excess H2O , excess solutes (glucose, salts),

toxins, drugs, “unknowns”

H2O

H2O

H2O

Maintaining Water BalanceGet morewater intoblood fast

Alcohol suppresses ADH…

makes youurinate a lot!

• High blood osmolarity level– too many solutes in blood

• dehydration, high salt diet– stimulates thirst = drink more – release ADH from pituitary gland

• antidiuretic hormone– increases permeability of collecting duct

& reabsorption of water in kidneys• increase water absorption back into blood• decrease urination

Maintaining Water Balance

• Low blood osmolarity level or low blood pressure– JGA releases renin in kidney– renin converts angiotensinogen to angiotensin– angiotensin causes arterioles to constrict

• increase blood pressure– angiotensin triggers release of aldosterone from adrenal

gland– increases reabsorption of NaCl & H2O in kidneys

• puts more water & salts back in blood

Get morewater & salt into

blood fast!

adrenalgland

nephron

low

Blood Osmolarity

blood osmolarityblood pressure

ADH

increasedwater

reabsorption

increasethirst

renin

increasedwater & saltreabsorption

high

Endocrine System Control

pituitary

angiotensinogenangiotensin

nephronadrenalgland

aldosterone

JuxtaGlomerularApparatus

Can animals switch? Salmon

• Vampire bats – drink a blood meal (high protein right?). They drink a ton and then can’t fly so they urinate lots of water on the spot. They fly to roost and don’t drink so excrete pasty urea (guano)