Transcript Introduction to Circulation - AP Biology 2012

Introduction to Circulation
AP Biology
Unit 6
Invertebrates with Gastrovascular
Cavities
• Don’t have a true circulatory
system
• Material exchange (gases,
nutrients, wastes) with the
environment occurs through
diffusion
• Why is diffusion effective here?
– The animals are only a few cell
layers thick– materials don’t have
to go across too many layers
• Example: Cnidarians
Slide 2 of 32
True Circulatory Systems
•
3 main components in a true circulatory
system:
1. Circulatory fluid (blood)
2. Tubes to transport fluid (blood vessels)
3. Muscular pump (heart)
Slide 3 of 32
True Circulatory Systems
• Blood pressure keeps the circulatory fluid
moving through the system (in addition to
other forces)
• Blood pressure = force exerted on the walls
of the blood vessels by the blood (caused
primarily by the pumping of the heart)
Slide 4 of 32
True Circulatory Systems
• In general, higher metabolism means a more
complex circulatory system
• An animal either has an open or a closed
circulatory system
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Open Circulatory Systems
• Blood and interstitial fluid
are the same (hemolymph)
• Low blood pressure (less
energy to circulate fluid)
• Simple system of tubes
– sinuses = spaces between
organs
– ostia = tubes that open to the
body environment
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Open Circulatory System
• The heart helps pump hemolymph around
• Hemolymph will also be pushed back into
the ostia as the animal moves around
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Closed Circulatory System
• Blood is confined to tubes, so it is different
from interstitial fluid
• Molecules diffuse between blood and
interstitial fluid
• High blood pressure
Slide 8 of 32
Question…
• Why would higher blood pressure be
beneficial?
– Can get blood to areas that need it more
efficiently
– Allows the organism to be more active
Slide 9 of 32
Closed Circulatory System
• Complex system of tubes
• arteries = vessels that carry
blood from heart to capillaries
(throughout body)
• veins = vessels that carry blood
from capillaries to heart (in
general)
• capillaries = tiny, porous vessels
through which molecules diffuse
in / out (throughout body)
Slide 10 of 32
General Circulatory Pathway
• Heart  artery  capillaries  vein 
back to heart
Slide 11 of 32
Comparison of Vertebrate
Circulation- Fish
• Gas exchange with the
environment occurs in the gills
• Blood pressure is highest in the
artery leaving the heart to go to
the lungs.
Slide 12 of 32
Comparison of Vertebrate
Circulation- Fish
• Blood in the heart is separated
(oxygenated and de-oxygenated
blood are not mixed together)
• Single circulation = blood goes
to the heart once (continues on
to the body without returning
after the lungs)
• 2 chambers in heart (1 atrium, 1
ventricle)
Slide 13 of 32
Comparison of Vertebrate
Circulation- Amphibian
• Gases are exchanged with the
environment in the lungs and
across the skin
• Blood pressure is highest
where blood leaves the heart
Slide 14 of 32
Comparison of Vertebrate
Circulation- Amphibian
• Blood in the heart is mixed–
deoxygenated and newly
oxygenated blood mix together
in ventricle
• Double circulation = blood is
pumped two times from the
heart– goes to the lungs, then
comes back to get pumped to
the rest of the body
• 3 chambers in heart (2 atria, 1
ventricle)
Slide 15 of 32
Comparison of Vertebrate
Circulation- Reptile
• Gas exchange occurs in the
lungs
• Blood pressure is where blood
is leaving the heart
Slide 16 of 32
Comparison of Vertebrate
Circulation- Reptile
• Blood in the heart is mixed-deoxygenated and newly
oxygenated blood mix together
in partially separated ventricle
• Double circulation
• 3 ½ chambers in heart (2 atria,
one partially separated ventricle)
– Only crocodiles have fully
separated ventricles
Slide 17 of 32
Question…
• What is the benefit of having double
circulation (compared to single circulation)?
– Blood can reach tissues more efficiently 
High blood pressure\
– This allows the organism to be more active
Slide 18 of 32
Reptile Circulation
• Reptiles also have a 2nd aorta
• Benefit?
– Can bypass the lungs when
underwater (no point in
sending blood to the lungs if
there can’t get O2 from them)
– Blood continues to flow to the
body tissues (so they can still
get some O2)  higher activity
Slide 19 of 32
Comparison of Vertebrate
Circulation- Mammal & Bird
• Gas Exchange occurs in the
lungs
• Blood pressure is where blood is
leaving the heart
• Blood is separated –
deoxygenated and newly
oxygenated blood do not mix
(held in separate chambers)
Slide 20 of 32
Comparison of Vertebrate
Circulation- Mammal & Bird
• Double circulation
• 4 chambers in heart (2 atria, 2
ventricles)
Slide 21 of 32
Question…
• Why is having separated (compared to
mixed blood) an advantage?
– If blood is mixed, then deoxygenated blood that
hasn’t gone to the lungs will also return to the
body
– Separated blood means that the blood returning
to the body is all fully re-oxygenated
Slide 22 of 32
Pressure and Metabolism
• The inability to maintain pressure over a
distance yields lower metabolism.
– Pressure decreases as blood flows through tiny
capillaries
• Which organism can have the highest
metabolic rate?
– Mammals and birds (in general)
Slide 23 of 32
Mammalian Heart
• 4 chambered heart (2
atria, 2 ventricles)
• Valves = flaps that keep
chambers of the heart
closed at the right time
• Valves are needed to
build pressure in heart
and prevent back-flow of
blood.
Slide 24 of 32
Right side
Left side
Atrioventricular (AV) Valves
• Located between the
atria and ventricles
• Tricuspid Valve
– Between the right atrium
and right ventricle
– 3 flaps
• Bicuspid (Mitral) valve
– Between the left atrium
and left ventricle
– 2 flaps
Slide 25 of 32
Semilunar valves
• located at two exits for
the heart
• Between the right
ventricle and the
pulmonary artery (to
lungs)
• Between the left
ventricle and the aorta
(to the body)
Slide 26 of 32
Pathway of Blood
• Do you remember the pathway of blood through
the body and the heart?
• Use these terms: Right Atrium, Left Atrium, Right
Ventricle, Left Ventricle, Pulmonary Artery,
Pulmonary Vein, Aorta, Lung Capillaries,
Capillaries in Top or Bottom of Body, Anterior /
Posterior Vena Cava
• Start where the blood first leaves the heart to go to
the body
Slide 27 of 32
Pathway of blood
• Aorta  arteries 
capillaries in body  veins
 vena cava  right
atrium  right ventricle 
pulmonary artery  lung
capillaries  pulmonary
vein  left atrium  left
ventricle  aorta
Slide 28 of 32
Questions…
• Where does the blood have the highest O2
concentration?
– Just after leaving lungs (where it picked up O2)
• Where does the blood have the highest CO2
concentration?
– Just before getting to the lungs (hasn’t dropped
off the CO2 waste yet)
Slide 29 of 32
Heartbeat
• The heart beat is controlled by
electrical signals generated in
specific cells in the heart =
self excitation
• Sinoatrial (SA) node = a group
of specialized cells that
initiates the heartbeat
– Also called the pacemaker of
the heart
– generates electrical impulses
that cause both atria to contract
Slide 30 of 32
Heartbeat
• Atrioventricular (AV) node
– When it receives the signals from the SA node,
it transfers the signals to the Bundle of His
• Bundle of His spreads the signal to the
Purkinje fibers in the ventricles  both
ventricles contract
• Pathway:
SA  AV 
Bundle of His
 Purkinje
Slide 31 of 32
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