Regulating the InternalEnvironment

Water Balance & Nitrogenous Waste

Removal

Conformers vs. Regulators • Two evolutionary paths for organisms

– Endothermy• maintain relatively constant internal conditions

– Ectothermy• 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

intracellular waste

extracellular waste

Animal systems evolved to support multicellular life

O2

CHO

CHO

aa

aa

CH

CO2

NH3aa

O2

CH

O2

aa

CO2

CO2

CO2

CO2

CO2

CO2 CO2

CO2

CO2

CO2

NH3

NH3 NH3

NH3

NH3

NH3

NH3NH3

O2

aa

CH

aa

CHO

O2

Diffusion too slow!

Overcoming limitations of diffusion• Evolution of exchange systems for

– distributing nutrients • Circulatory

– removing wastes• Excretory

systems to support multicellular organisms

systems to support multicellular organisms

aa

CO2

CO2

CO2

CO2

CO2

CO2 CO2

CO2

CO2

CO2

NH3

NH3 NH3

NH3

NH3

NH3

NH3NH3

O2

aa

CH

aa

CHO

O2

Osmoregulation

Why do all land animals have to conserve 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–

lots!verylittle

Nitrogenous waste disposal• Ammonia (NH3)

– Carcinogenic– 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

Nitrogen waste• Aquatic animals

– can afford to lose water – _Ammonia_______

• most toxic

• Terrestrial Animals– need to conserve

water– _Urea___________

• less toxic

• Terrestrial Egg Layers– need to conserve water– need to protect

embryo in egg– _Uric Acid______

• least toxic

Freshwater animals• Water removal & nitrogen waste disposal

– remove surplus water• use surplus water to dilute ammonia & excrete it

– need to excrete a lot of water so dilute ammonia & excrete it as very dilute urine

• also diffuse ammonia continuously through gills or through any moist membrane

– overcome loss of salts• reabsorb in kidneys or active transport across gills

Land animals• Nitrogen waste disposal on land

– need to conserve water– must process ammonia so less toxic

• Urea = larger molecule = less soluble = less toxic– 2NH2 + CO2 = urea– produced in liver

– Kidney_______• filter solutes out of blood• reabsorb H2O (+ any useful solutes)• excrete waste

– Urine = urea, salts, excess sugar & H2O » urine is very concentrated» concentrated NH3 would be too toxic

OC

HNH

HNH

mammals

Egg-laying land animals• Nitrogen waste disposal in egg

– no place to get rid of waste in egg– need even less soluble molecule

• Uric Acid = BIGGER = less soluble = less toxic

– birds, reptiles, insects

N

N N

N

O

HO

O

H

HH

Uric acid• Polymerized urea

– large molecule– Requires more energy to make– Relatively non-toxic

• doesn’t harm embryo in egg– white dust in egg

• adults excrete N waste as white paste– no liquid waste– urea = white bird “poop”!

Mammalian System• Filter solutes out of blood &

reabsorb H2O + desirable solutes• Key functions

– Filtration• fluids (water & solutes) filtered out

of blood

– Reabsorption• selectively reabsorb (diffusion)

needed water + solutes back to blood

– Secretion• pump out any other unwanted

solutes to urine

– Excreation• 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 pressure forces blood

into nephron• high pressure flow

– Proximal tubule, loop of Henle and distal tubule reabsorb valuable solutes & H2O back into bloodstream

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– Bowman’s capsule– Proximal tubule– Loop of Henle

• descending limb• ascending limb

– Distal tubule– Collecting duct

Bowman’s capsule

Na+ Cl-

Osmotic control in nephron• How is all this re-absorption achieved?

– tight osmotic control to reduce the energy cost of excretion

– use diffusion instead of active transportwherever possible

Any Questions?

Regulating the InternalEnvironment

Maintaining Homeostasis

sensor

Negative Feedback Loop

high

low

hormone or nerve signal

lowersbody condition(return to set point)

hormone or nerve signal

gland or nervous system

raisesbody condition (return to set point)

gland or nervous system

sensor

specific body condition

Controlling Body Temperature

high

low

nerve signals

sweat

nerve signals

body temperature

shiver brain

dilates surfaceblood vessels

constricts surfaceblood vessels

Nervous System Control

brain

nephron

low

Blood Osmolarity

blood osmolarityblood pressure

ADH

increasedwater

reabsorption

increasethirst

high

Endocrine System Control

pituitary

ADH = AntiDiuretic Hormone

H2O

H2O

H2O

Maintaining Water Balance• 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

low

Blood Osmolarity

blood osmolarityblood pressure

increasedwater & saltreabsorption

in kidney

high

Endocrine System Control

angiotensigenangiotensin

nephronadrenalgland

aldosterone

JGA

JGA = JuxtaGlomerular Apparatus

rennin

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 adrenal

gland

nephron

low

Blood Osmolarity

blood osmolarityblood pressure

ADH

increasedwater

reabsorption

increasethirst

renin

increasedwater & saltreabsorption

high

Endocrine System Control

pituitary

angiotensinogenangiotensin

nephronadrenalgland

aldosterone

JuxtaGlomerularApparatus

Don’t get batty…

Ask Questions!!