Post on 13-Jan-2023
AP Biology
Exchange of materialsAnimal cells exchange material across their cell membrane
fuels for energy nutrients oxygen waste (urea, CO2)
If you are a 1-cell organism that’s easy!If you are many-celled that’s harder
AP Biology
Overcoming limitations of diffusion
O2CHO
CHO
aa
aa
CH
CO2
NH3aa
O2
CH
aa
CO2CO2
CO2
CO2CO2
CO2 CO2
CO2
CO2
CO2
NH3
NH3 NH3
NH3
NH3
NH3
NH3NH3
O2
aa
CH
aa
CHO
O2
Diffusion is not adequate for moving material across more than 1-cell barrier
AP Biology
In circulation…What needs to be transported
nutrients & fuelsfrom digestive system
respiratory gasesO2 & CO2 from & to gas exchange systems: lungs, gills
intracellular wastewaste products from cells
water, salts, nitrogenous wastes (urea)protective agents
immune defenseswhite blood cells & antibodies
blood clotting agentsregulatory molecules
hormones
AP Biology
Circulatory systemsAll animals have:
circulatory fluid = “blood”tubes = blood vesselsmuscular pump = heart
open closed
hemolymph blood
AP Biology
Open circulatory systemTaxonomy
invertebratesinsects, arthropods, mollusks
Structureno separation between blood & interstitial fluid
hemolymph
AP Biology
Closed circulatory systemTaxonomy
invertebratesearthworms, squid, octopuses
vertebratesStructure
blood confined to vessels & separate from interstitial fluid
1 or more heartslarge vessels to smaller vesselsmaterial diffuses between vessels & interstitial fluid
closed system = higher pressures
AP Biology
Vertebrate circulatory systemAdaptations in closed system
number of heart chambers differs
4 chamber heart is double pump = separates oxygen-rich & oxygen-poor blood; maintains high pressure
What’s the adaptive value of a 4 chamber heart?
2 3 4
low pressure to body
low O2 to body
high pressure & high O2 to body
AP Biology
Evolution of vertebrate circulatory system
fish amphibian reptiles birds & mammals
A A
VV V VV
A AAAA
V
2 chamber 3 chamber 3 chamber 4 chamber
Birds AND
mammals!
Wassssup?!
AP Biology
Evolution of 4-chambered heart
convergent evolution
Selective forces↑ body size
protection from predationbigger body = bigger stomach for herbivores
endothermycan colonize more habitats
flightdecrease predation & increase prey capture
Effect of higher metabolic rategreater need for energy, fuels, O2, waste removal
endothermic animals need 10x energyneed to deliver 10x fuel & O2 to cells
AP Biology
Vertebrate cardiovascular systemChambered heart
atrium = receive bloodventricle = pump blood out
Blood vesselsarteries = carry blood away from heart
arteriolesveins = return blood to heart
venulescapillaries = point of exchange, thin wall
capillary beds = networks of capillaries
AP Biology
Blood vesselsarteries
arterioles
capillaries
venules
veins
artery
arteriolesvenules
veins
AP Biology
Arteries: Built for high pressure pumpArteries
thicker walls provide strength for high pressure pumping of blood
narrower diameterelasticity
elastic recoil helps maintain blood pressure even when heart relaxes
AP Biology
Veins: Built for low pressure flowVeins
thinner-walled wider diameter
blood travels back to heart at low velocity & pressurelower pressure
distant from heartblood must flow by skeletal muscle contractions when we move
squeeze blood through veins
valvesin larger veins one-way valvesallow blood to flow only toward heart
Open valve
Blood flowstoward heart
Closed valve
AP Biology
Capillaries: Built for exchangeCapillaries
very thin walls lack 2 outer wall layers only endothelium
enhances exchange across capillary
AP Biology
Controlling blood flow to tissuesBlood flow in capillaries controlled by pre-capillary sphincters
supply varies as blood is neededafter a meal, blood supply to digestive tract increasesduring strenuous exercise, blood is diverted from digestive tract to skeletal muscles
capillaries in brain, heart, kidneys & liver usually filled to capacity
sphincters open sphincters closed
Why?
AP Biology
Exchange across capillary walls
Arteriole
Bloodflow
Venule
Lymphaticcapillary
Interstitialfluid
Fluid & solutes flows out of capillaries to tissues due to blood pressure
“bulk flow”
Interstitial fluid flows back into capillaries due to osmosis
plasma proteins ↑ osmotic pressure in capillary
BP > OP BP < OP
15% fluid returns via lymph
85% fluid returns to capillaries
What about
edema?
Capillary
AP Biology
Lymphatic systemParallel circulatory system
transports white blood cellsdefending against infection
collects interstitial fluid & returns to blood
maintains volume & protein concentration of blooddrains into circulatory system near junction of vena cava & right atrium
AP Biology
Mammalian circulation
What do blue vs. red areas represent?What do blue vs. red areas represent?
pulmonary
systemic
systemic
AP Biology
AV
SL
AV
Heart valves4 valves in the heart
flaps of connective tissueprevent backflow
Atrioventricular (AV) valvebetween atrium & ventriclekeeps blood from flowing back into atria when ventricles contract
“lub”Semilunar valves
between ventricle & arteriesprevent backflow from arteries into ventricles while they are relaxing
“dub”
AP Biology
AV
SL
AV
Lub-dub, lub-dubHeart sounds
closing of valves“Lub”
recoil of blood against closed AV valves
“Dub”recoil of blood against semilunar valves
Heart murmurdefect in valves causes hissing sound when stream of blood squirts backward through valve
AP Biology
Cardiac cycle
systolic________diastolic
pump (peak pressure)_________________fill (minimum pressure)
1 complete sequence of pumpingheart contracts & pumpsheart relaxes & chambers fill contraction phase
systoleventricles pumps blood out
relaxation phasediastoleatria refill with blood
AP Biology
Measurement of blood pressure
High Blood Pressure (hypertension)if top number (systolic pumping) > 150if bottom number (diastolic filling) > 90