Introduction to CirculationIntroduction to Circulation

AP BiologyUnit 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: CnidariansSlide 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)

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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)

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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

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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

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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)

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General Circulatory Pathway

• Heart artery capillaries vein back to heart

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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.

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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)

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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

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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)

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Comparison of Vertebrate Circulation- Reptile

• Gas exchange occurs in the lungs

• Blood pressure is where blood is leaving the heart

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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

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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

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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

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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)

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Comparison of Vertebrate Circulation- Mammal & Bird

• Double circulation

• 4 chambers in heart (2 atria, 2 ventricles)

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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

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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)

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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.

Right side Left side

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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

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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)

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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

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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

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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)

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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

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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

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