1. Chapter 23
Circulation

2. 23.1 - 23.5 INTRO TO CIRCULATORY SYSTEMS
INTRO TO CIRCULATORY SYSTEMS
© 2012 Pearson Education, Inc. 2

3. Function of CV System
Circulatory systems facilitate exchange with all body tissues
All cells must
receive nutrients,
exchange gases, and
remove wastes.
Diffusion alone is inadequate for large and complex bodies.
In most animals, circulatory systems facilitate these exchanges.
Assists diffusion by moving materials between
surfaces of the body and Internal tissues.
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system in which water, under high pressure, is contained in pipes. The analogy is not perfect, because water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
© 2012 Pearson Education, Inc. 3

4. Simple Gastrovascular Cavity is Found in Cnidarians and Flatworms
Cnidarians = jellyfish and hydra
Notice only one opening in/out!
Gastrovascular cavity serves both in digestion and distribution of substances throughout body
This is adequate for these organisms as they are only two layers of cells thick - all cells can exchange materials directly with water.
polyp
medusa
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system in which water, under high pressure, is contained in pipes. The analogy is not perfect, because water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
© 2012 Pearson Education, Inc. 4

5. Flatworms - We’re so flat because we exchange materials directly with environment.
Only ONE entrance/exit! YIKES!!
Gastrovascular
cavity
Nerve cords
Mouth/Anus
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system in which water, under high pressure, is contained in pipes. The analogy is not perfect, because water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
Eyecups
Nervous
tissue clusters
Bilateral symmetry
© 2012 Pearson Education, Inc. 5

6. Mouth Gastrovascular cavity Diffusion Diffusion Diffusion Single cell
Small organisms have sufficient SA:volume ratio that they do not require a specialized circulatory system.
Mouth
Gastrovascular
cavity
Diffusion
Diffusion
Diffusion
Single cell
Two cell layers

7. Large, more complex organisms require a true circulatory system
Most animals use a true circulatory system that consists of a
circulatory fluid (blood),
muscular pump (heart), and
set of tubes (blood vessels) to carry the fluid.
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system in which water, under high pressure, is contained in pipes. The analogy is not perfect, because water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
© 2012 Pearson Education, Inc. 7

8. EXTERNAL ENVIRONMENT
But large, complex organisms require true CV system to maintain sufficient SA:volume ratio
CO2
Food O2
Mouth
ANIMAL B l o d
Respiratory system
Digestive system
Interstitial fluid
Heart
Nutrients
Circulatory system
Body cells
Figure 20.13A A schematic representation showing indirect exchange between the environment and the cells of a complex animal
Urinary system
Intestine
Anus
Unabsorbed matter (feces)
Metabolic waste products (urine) 8

9. 2 Types of Circulatory Systems
Open circulatory systems are found in arthropods and many molluscs and consist of
a heart,
open-ended vessels, and
blood that directly bathes the cells and functions as the interstitial fluid.
Tubular heart
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system in which water, under high pressure, is contained in pipes. The analogy is not perfect, because water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
Pores
© 2012 Pearson Education, Inc. 9

10. Two Types of Circulatory Systems
Closed circulatory systems are found in vertebrates, earthworms, squids, and octopuses and consist of
a heart and
vessels that confine blood, keeping it distinct from interstitial fluid.
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system in which water, under high pressure, is contained in pipes. The analogy is not perfect, because water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
© 2012 Pearson Education, Inc. 10

11. Three Types of Blood Vessels Found in CV Systems
1. Arteries carry blood away from the heart.
2. Veins return blood to the heart.
3. Capillaries convey blood between arteries and veins.
Capillary beds
Arteriole
Artery (O2-rich blood)
Venule
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. If you have not included Chapter 20 in your course, you may want to show your class Figure 20.13A. This figure provides a general demonstration of the types of systems required by organisms too large to exchange all materials at the surface of the body.
2. A gastrovascular cavity, seen in cnidarians and flatworms, absorbs and distributes nutrients throughout the organism’s body. The word root vascula (meaning “little vessel”) represents the circulatory function of these systems. As noted in Module 23.1, gastrovascular cavities are not effective in larger animals.
3. The following analogy to a house might help students distinguish between open and closed circulatory systems. The flow of air through a home with a blower furnace is an open system, in which the furnace propels air through ducts that open into rooms, and the air is later collected by vents that channel air back to the furnace. In this open system, air pressure and currents are generally low. In contrast, the plumbing systems of most homes are much more like a closed system in which water, under high pressure, is contained in pipes. The analogy is not perfect, because water pipes do eventually open up into sinks and bathrooms, before draining into the sewage system.
4. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
5. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
6. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
Vein
Atrium
Gill capillaries
Heart
Artery (O2-poor blood)
Ventricle
© 2012 Pearson Education, Inc. 11

12. Vertebrate cardiovascular systems reflect evolution
Closed circulatory systems may exhibit:
In single circulation blood moves
from gill capillaries,
to systemic (body) capillaries, and
back to the heart.
Blood pressure drops significantly as blood flows thru gill capillaries
Single circuit would never provide enough pressure to push blood thru the lungs and rest of body in a terresterial (land) animal.
Characteristic of fish.
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
3. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
4. The three-chambered heart of amphibians and turtles should not be seen as a necessary “intermediate” stage in some predestined evolution of a four-chambered heart. Instead, the three-chambered heart conveys advantages not permitted by the complete subdivision of the ventricle. In amphibians and turtles, the circuit to the lungs can be bypassed when diving underwater. When breathing is not possible, blood can be rerouted past the lungs. Thus, a loss in efficiency conveys an advantage in flexibility. This fundamental principle, in which efficiency and flexibility are traded against each other, is illustrated in many systems in living organisms.
© 2012 Pearson Education, Inc. 12

13. Gill capillaries Heart: Ventricle Atrium Body capillaries Figure 23.2A
Figure 23.2A The single circulation and two-chambered heart of a fish
Body capillaries 13

14. Double circulation double circulation consists of a separate
double circulation consists of a separate
pulmonary circuit (heart to lungs and back to heart)
systemic circuit (heart to body tissue and back to heart)
Found in land animals - amphibians, reptiles, birds, mammals
Allows for a second ‘push’ of blood returning from lungs to provide enough pressure for blood to travel without organism’s body.
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
3. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
4. The three-chambered heart of amphibians and turtles should not be seen as a necessary “intermediate” stage in some predestined evolution of a four-chambered heart. Instead, the three-chambered heart conveys advantages not permitted by the complete subdivision of the ventricle. In amphibians and turtles, the circuit to the lungs can be bypassed when diving underwater. When breathing is not possible, blood can be rerouted past the lungs. Thus, a loss in efficiency conveys an advantage in flexibility. This fundamental principle, in which efficiency and flexibility are traded against each other, is illustrated in many systems in living organisms.
© 2012 Pearson Education, Inc. 14

15. Pulmocutaneous circuit
Figure 23.2B
Lung and skin capillaries
Pulmocutaneous circuit
Atrium
Atrium
Figure 23.2B The double circulation and three-chambered heart of an amphibian
Ventricle
Right
Left
Systemic circuit
Systemic capillaries 15

16. Four Chambered hearts are essential for organism with high metabolic rates (energy demands)
Four-chambered hearts
are found in crocodilians, birds, and mammals and
consist of
two atria and
two ventricles.
Birds, mammals and crocodiles are warm-blooded (endotherms) and thus require much greater rates of cellular respiration (thus more O2) to meet energy demands
Prevents oxygen-rich and oxygen-poor blood from mixing and keeps pulmonary and systemic circuits completely separate
oxygen-rich and
oxygen-poor blood.
Student Misconceptions and Concerns
1. Students might need to be reminded about the changes in surface-to-volume ratios as organisms increase in size. As any organism gets larger (maintaining the same proportions) the need for a circulatory system coupled with a respiratory system increases, since the increase in surface area does not keep up with the increase in volume.
2. Students might not realize that closed circulatory systems are capable of greater pressures when fluids remain confined to limited spaces.
Teaching Tips
1. Challenge students to explain why closed circulatory systems have evolved in squids and octopuses, but not in clams or snails. The greater amount of muscular activity in squids and octopuses may have favored these more efficient systems of delivery.
2. To help students understand the need for a circulatory system, consider this analogy. Small islands are like small animals: No inner part is very far from the edges. However, large countries, like large animals, have considerable interior areas located far from their borders. Therefore, large countries such as the United States, Canada, and China require an internal system of roads and railways to transport many goods from ocean ports to cities located deep in these countries. These roads and railways move materials from ports in the same way that blood and blood vessels move them from respiratory surfaces.
3. There are many simple demonstrations of diffusion that can be performed. If you use a video imager or overhead projector, add a single drop of food coloring into a beaker of water with bright illumination. The slow dissipation of the dye will serve as a colorful and dramatic example of materials moving from a higher to a lower level of concentration.
4. The three-chambered heart of amphibians and turtles should not be seen as a necessary “intermediate” stage in some predestined evolution of a four-chambered heart. Instead, the three-chambered heart conveys advantages not permitted by the complete subdivision of the ventricle. In amphibians and turtles, the circuit to the lungs can be bypassed when diving underwater. When breathing is not possible, blood can be rerouted past the lungs. Thus, a loss in efficiency conveys an advantage in flexibility. This fundamental principle, in which efficiency and flexibility are traded against each other, is illustrated in many systems in living organisms.
© 2012 Pearson Education, Inc. 16

17. Pulmonary circuit Systemic circuit
Figure 23.2C
Lung capillaries
Pulmonary circuit
Figure 23.2C The double circulation and four-chambered heart of a bird or mammal
Atrium
Atrium
Ventricle
Ventricle
Right
Left
Systemic circuit
Systemic capillaries 17

18. THE HUMAN CARDIOVASCULAR SYSTEM AND HEART
THE HUMAN CARDIOVASCULAR SYSTEM AND HEART
© 2012 Pearson Education, Inc. 18

19. Blood flow through the human CV circuits
Blood flow through the double circulatory system of humans
drains from the superior vena cava (from the head and arms) or inferior vena cava (from the lower trunk and legs) into the right atrium,
moves out to the lungs via the pulmonary artery,
returns to the left atrium through the pulmonary vein, and
leaves the heart through the aorta.
Teaching Tips
When discussing the way blood flows through four-chambered hearts, it is helpful to remind students that the heart is essentially two pumps. The right side collects from the body and propels to the lungs; the left side propels from the lungs out to the body. Having them memorize this sequence as right-to-left helps students recall the correct atrial and ventricular sequences.
Animation: Path of Blood Flow in Mammals
© 2012 Pearson Education, Inc. 19

20. Capillaries of head, chest and arms Superior vena cava
Figure 23.3A 8
Capillaries of head, chest and arms
Superior vena cava
Pulmonary artery
Pulmonary artery
Aorta 9
Capillaries of right lung
Capillaries of left lung 2 7 2 3 3 5 4 10 4
Pulmonary vein
Pulmonary vein 6 1 9
Right atrium
Left atrium
Figure 23.3A Blood flow through the double circulation of the human cardiovascular system
Left ventricle
Right ventricle
Aorta
Inferior vena cava
Capillaries of abdominal region and legs 8 20

21. Note: arteries take blood AWAY from heart
D1 _Pulmonary artery (to lung)
H ___Aorta________
A1 _superior vena cava_
D2 _Pulmonary artery
(to lung)
B _right atrium__
F left atrium
E2 Pulmonary vein
(from lung)
E1 Pulmonary vein
(from lung)
Note: Atria accept blood to heart; ventricles pump blood out - therefore have much more muscular walls.
Note: arteries take blood AWAY from heart
Veins take blood to heart
A2 _inferior vena cava_
C _right ventricles
G _left ventricle

22. The Cardiac Cycle
The repeated contraction and relaxation of pumping blood is called the cardiac cycle. The cycle consists of two main phases.
During diastole, heart relaxes and all chambers fill with blood
During systole, heart contracts and blood flows
from atria into ventricles
Then from ventricles into arteries
Student Misconceptions and Concerns
Students often expect that the blood flowing through the heart supplies the heart muscle. The need for coronary arteries and veins is not clear to them. (The thickness of the walls of the heart does not permit efficient diffusion, and furthermore, the oxygen content of the blood in the right atrium and ventricle is very low.)
Teaching Tips
1. Students often benefit from brief, concrete demonstrations of abstract ideas. When discussing the cardiac cycle, take the time to have students quickly take their own pulses as they are seated in class to help them relate the lecture topic to their own anatomy. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander.
2. Having students take their own pulses also provides an opportunity to stimulate further curiosity. You may want to assign students to measure and record the variation in their pulse rates during the day’s different activities, perhaps (a) upon arrival to a class and after 20 minutes sitting in the class, (b) before and after drinking coffee, or (c) prior to and during exercise.
© 2012 Pearson Education, Inc. 22

23. Diastole The semilunar valves are closed. The heart is relaxed.
Figure 23.4_s1
Diastole
The semilunar valves are closed. 1
The heart is relaxed.
All chambers
fill with blood
Figure 23.4_s1 A cardiac cycle in a human with a heart rate of about 72 beats a minute (step 1)
0.4 sec
The AV valves are open. 23

24. Diastole Systole Pushes blood into ventricles
Figure 23.4_s2
Diastole
Systole
The semilunar valves are closed. 1
The heart is relaxed. 2
The atria contract.
Pushes blood into
ventricles
0.1 sec
Figure 23.4_s2 A cardiac cycle in a human with a heart rate of about 72 beats a minute (step 2)
0.4 sec
The AV valves are open. 24

25. Diastole Systole The semilunar valves are closed.
Figure 23.4_s3
Diastole
Systole
The semilunar valves are closed. 1
The heart is relaxed. 2
The atria contract.
0.1 sec 3
The ventricles contract.
Ventricles pump
Blood out thru
arteries
Figure 23.4_s3 A cardiac cycle in a human with a heart rate of about 72 beats a minute (step 3)
0.3 sec
0.4 sec
The AV valves are open.
The AV valves are closed. 25

26. 23.4 The heart contracts and relaxes rhythmically
Cardiac output is the amount of blood pumped per minute from the ventricles.
Cardiac output = Heart rate x volume of blood pumped with each contraction
Heart rate = is the number of heart beats per minute.
Heart rate and cardiac output vary with physiological conditions
Athletes have high CO even with low heart rates due to increased blood volume acquired from training
Student Misconceptions and Concerns
Students often expect that the blood flowing through the heart supplies the heart muscle. The need for coronary arteries and veins is not clear to them. (The thickness of the walls of the heart does not permit efficient diffusion, and furthermore, the oxygen content of the blood in the right atrium and ventricle is very low.)
Teaching Tips
1. Students often benefit from brief, concrete demonstrations of abstract ideas. When discussing the cardiac cycle, take the time to have students quickly take their own pulses as they are seated in class to help them relate the lecture topic to their own anatomy. This very short activity will provide a small break in the lecture routine and refocus the attention of those students whose minds may have begun to wander.
2. Having students take their own pulses also provides an opportunity to stimulate further curiosity. You may want to assign students to measure and record the variation in their pulse rates during the day’s different activities, perhaps (a) upon arrival to a class and after 20 minutes sitting in the class, (b) before and after drinking coffee, or (c) prior to and during exercise.
© 2012 Pearson Education, Inc. 26

27. 23.5 The SA node sets the tempo of the heartbeat
The SA (sinoatrial) node
generates electrical signals in atria and
sets the rate of heart contractions.
Called the pacemaker of the heart
SA Node receives nervous signal info from central nervous system and relays these changes in heart rate to rest of heart to coordinate cardiac cycle and heart rate. 1
Signals from the SA node spread through the atria.
SA node (pacemaker)
Student Misconceptions and Concerns
Students often expect that the blood flowing through the heart supplies the heart muscle. The need for coronary arteries and veins is not clear to them. (The thickness of the walls of the heart does not permit efficient diffusion, and furthermore, the oxygen content of the blood in the right atrium and ventricle is very low.)
Teaching Tips
1. The specialized junctions that promote signal conduction between cardiac cells are specifically identified in Figure 20.6 in Chapter 20.
2. Before explaining the functions of the SA node, consider asking your students to explain why the atria contract before the ventricles contract. Posing a question and asking for an explanation rather than simply lecturing students often generates a more active interest in the subject matter.
Right atrium
ECG
© 2012 Pearson Education, Inc. 27