Chapter 23 Circulation 2

Blood starts in the Right Atrium, where to next Blood starts in the Right Atrium, where to next? Put the following in order: Correct Order Right Ventricle Pulmonary Arteries Capillaries of Lungs Pulmonary Veins Left Atrium Left Ventricle Aorta Capillary beds of body Vena Cava Left Ventricle Capillaries of Lungs Vena Cava Right Ventricle Capillary beds of body Pulmonary Veins Left Atrium Aorta Pulmonary Arteries http://media.pearsoncmg.com/bc/bc_campbell_concepts_6/activities/cmr3Lib/activitie s/B23/B2301/st01/frame.html http://media.pearsoncmg.com/bc/bc_0media_bio/blast/index.htm?heart_anatomy

The SA node sets the tempo of the heartbeat The SA (sinoatrial) node generates electrical signals in atria 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) Right atrium 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. ECG © 2012 Pearson Education, Inc. 3

The SA node sets the tempo of the heartbeat The AV (atrioventricular) node Relays these signals to the ventricles Causes ventricular contraction 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. © 2012 Pearson Education, Inc. 4

ECG Animations http://media.pearsoncmg.com/bc/bc_0media_bio/blast/index.htm?electrical_coord_cardiac http://www.youtube.com/watch?v=v3b-YhZmQu8 http://www.youtube.com/watch?v=WuKTkPJE-SE&feature=share&list=PLDEDCBEBFD0F37DC7

Electrical Activity of Myocardium Atrial depolarization begins Atrial depolarization complete (atria contracted) Ventricles begin to depolarize at apex; atria repolarize (atria relaxed)

Electrical Activity of Myocardium Ventricular depolarization complete (ventricles contracted) Ventricles begin to repolarize at apex Ventricular repolarization complete (ventricles relaxed)

ECGs, Normal & Abnormal No P waves

ECGs, Abnormal Arrhythmia: conduction failure at AV node No pumping action occurs

Heart Sounds Auscultation - listening to sounds made by body First heart sound (S1), louder and longer “lubb”, occurs with closure of AV valves Second heart sound (S2), softer and sharper “dupp” occurs with closure of semilunar valves S3 - rarely heard in people > 30 Examples

A B C A = Pulnomic Stenosis B = Normal C = Aortic Stenosis Early Which of the following do you think is a normal heart sound? A B C http://depts.washington.edu/physdx/heart/demo.html A = Pulnomic Stenosis B = Normal C = Aortic Stenosis Early

Where to listen on chest wall for heart sounds.

Heart Contractions Listen to your hearts.

What is a Heart Attack?

Heart Attack Atherosclerosis

STRUCTURE AND FUNCTION OF BLOOD VESSELS STRUCTURE AND FUNCTION OF BLOOD VESSELS © 2012 Pearson Education, Inc. 17

23.7 The structure of blood vessels fits their functions Capillaries Function: only vessels involved in exchange of solutes and fluid between blood and interstitial fluid. Structure: have thin walls consisting of a single layer of epithelial cells, are narrow, about as wide as one red blood cell, and Structure allows for increased surface area to facilitate gas and fluid exchange Student Misconceptions and Concerns Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen-poor blood, the pulmonary artery transports low-oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or toward the heart). Due to their structure, arteries are better able to resist the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. Teaching Tips 1. The photo in Figure 23.7A demonstrates the narrow width of capillaries. Notice that the diameter of the capillaries barely permits the passage of red blood cells. (Also note that Figure 23.7B shows a capillary diameter much greater than in the photograph.) Challenge your students to explain why such a small size is adaptive. (Answer: it increases the surface area of capillaries and places red blood cells adjacent to the capillary walls for efficient gas exchange.) 2. One function of the circulatory system that is rarely discussed is the transport of heat. Blood vessels near the surface of the body expand when the body is overheated, releasing some of this excess heat to the environment. Conversely, during periods of exposure to cold, blood is shunted away from the skin to conserve heat. 3. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure. © 2012 Pearson Education, Inc. 18

Diffusion of molecules Interstitial fluid Capillary Red blood cell Capillary Figure 23.7A A capillary in smooth muscle tissue Diffusion of molecules Interstitial fluid Tissue cell 19

The structure of blood vessels fits their functions Arteries and Veins are lined by a single layer of epithelial cells connective tissue layer and smooth muscle that allows these vessels to recoil after stretching. Arteries: Largest in diameter of all vessels thickest layer of smooth muscle in their walls Allows them to constrict and reduce blood flow Deal with higher blood pressure and exhibit increased elasticity Veins: have one-way valves that restrict backward flow of blood. Student Misconceptions and Concerns Students may need to be reminded of the definitions of an artery and vein, especially when discussing blood flow to and from the heart. Although veins generally carry oxygen-poor blood, the pulmonary artery transports low-oxygen blood to the lungs. The main difference between arteries and veins is the direction of flow (away from or toward the heart). Due to their structure, arteries are better able to resist the higher pressures generated by ventricular contractions. Veins generally experience lower pressure and are structurally less resistant. Teaching Tips 1. The photo in Figure 23.7A demonstrates the narrow width of capillaries. Notice that the diameter of the capillaries barely permits the passage of red blood cells. (Also note that Figure 23.7B shows a capillary diameter much greater than in the photograph.) Challenge your students to explain why such a small size is adaptive. (Answer: it increases the surface area of capillaries and places red blood cells adjacent to the capillary walls for efficient gas exchange.) 2. One function of the circulatory system that is rarely discussed is the transport of heat. Blood vessels near the surface of the body expand when the body is overheated, releasing some of this excess heat to the environment. Conversely, during periods of exposure to cold, blood is shunted away from the skin to conserve heat. 3. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure. © 2012 Pearson Education, Inc. 20

Epithelium Basal lamina Capillary Valve Epithelium Epithelium Figure 23.7C Epithelium Basal lamina Capillary Valve Epithelium Epithelium Smooth muscle Smooth muscle Connective tissue Connective tissue Artery Vein Figure 23.7C Structural relationships of blood vessels Arteriole Venule 21

Blood pressure and velocity Blood pressure is the force blood exerts on vessel walls, depends on: cardiac output (volume of blood and heart rate) resistance of vessels to expansion decreases as blood moves away from the heart. Student Misconceptions and Concerns Students often struggle to explain how blood is propelled up their legs to return to their hearts. Frequently, students will suggest that the heart itself must provide sufficient force to move blood completely around the body. However, such pressures would destroy delicate capillaries. Other student hypotheses might include attributing a negative, siphoning effect to the heart. (Although the heart can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thinking and motivate them to learn the answer. After explaining the role of skeletal muscles and one-way valves in veins, you might also note that it has been suggested that students will be more alert in class and even perform better on tests if they wiggle their legs. Challenge students to explain why this might work and why locking their knees when standing might have the opposite effect. (And enjoy watching some of your students deliberately wiggling their legs on the next exam!) Teaching Tips 1. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure. 2. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty by simply lifting their hands up to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 3. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand,” students may better understand the propulsive forces moving venous blood back to the heart. © 2012 Pearson Education, Inc. 22

Blood pressure and velocity Blood pressure is highest in arteries and lowest in veins. Blood pressure is measured as systolic pressure — caused by ventricular contraction diastolic pressure — low pressure between contractions Student Misconceptions and Concerns Students often struggle to explain how blood is propelled up their legs to return to their hearts. Frequently, students will suggest that the heart itself must provide sufficient force to move blood completely around the body. However, such pressures would destroy delicate capillaries. Other student hypotheses might include attributing a negative, siphoning effect to the heart. (Although the heart can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thinking and motivate them to learn the answer. After explaining the role of skeletal muscles and one-way valves in veins, you might also note that it has been suggested that students will be more alert in class and even perform better on tests if they wiggle their legs. Challenge students to explain why this might work and why locking their knees when standing might have the opposite effect. (And enjoy watching some of your students deliberately wiggling their legs on the next exam!) Teaching Tips 1. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure. 2. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty by simply lifting their hands up to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 3. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand,” students may better understand the propulsive forces moving venous blood back to the heart. © 2012 Pearson Education, Inc. 23

Pressure (mm Hg) Velocity (cm/sec) Figure 23.8A 120 Systolic pressure 100 Pressure (mm Hg) 80 60 Diastolic pressure 40 20 Relative sizes and numbers of blood vessels 50 40 Velocity (cm/sec) 30 Figure 23.8A Blood pressure and velocity in the blood vessels 20 10 Aorta Veins Arteries Venules Arterioles Capillaries Venae cavae 24

How does blood travel against gravity, up legs? Blood pressure and velocity reflect the structure and arrangement of blood vessels How does blood travel against gravity, up legs? Veins are squeezed by pressure from muscle contractions between two muscles or muscles and bone or skin. One-way valves limit blood flow to one direction, toward the heart. Direction of blood flow in vein Valve (open) Contracting skeletal muscle Valve (closed) Student Misconceptions and Concerns Students often struggle to explain how blood is propelled up their legs to return to their hearts. Frequently, students will suggest that the heart itself must provide sufficient force to move blood completely around the body. However, such pressures would destroy delicate capillaries. Other student hypotheses might include attributing a negative, siphoning effect to the heart. (Although the heart can generate a small pull, it is not sufficient to return blood up their legs and trunk to the heart.) Let them wonder long enough to stimulate critical thinking and motivate them to learn the answer. After explaining the role of skeletal muscles and one-way valves in veins, you might also note that it has been suggested that students will be more alert in class and even perform better on tests if they wiggle their legs. Challenge students to explain why this might work and why locking their knees when standing might have the opposite effect. (And enjoy watching some of your students deliberately wiggling their legs on the next exam!) Teaching Tips 1. Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure. 2. Veins on the back of our hands can reveal many of these same principles of venous blood flow. If students keep their hands down below their heart for several minutes, such as during note taking or typing, they might notice their veins starting to bulge. Students can watch the veins empty by simply lifting their hands up to eye level. As we get older, such phenomena are even easier to see. Some instructors may be comfortable enough (and old enough!) to demonstrate this effect to their students. 3. Contracting the hand into a fist helps propel blood back up the arms to the heart. Skin pulled tight on the back of the hand compresses veins against the underlying ligaments and bones. With this example “in hand,” students may better understand the propulsive forces moving venous blood back to the heart. © 2012 Pearson Education, Inc. 25

CONNECTION: Measuring blood pressure can reveal cardiovascular problems A typical blood pressure for a healthy young adult is about 120/70. Hypertension is a serious cardiovascular problem in which blood pressure is persistent at or above 140 systolic and/or 90 diastolic. Teaching Tips Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure. © 2012 Pearson Education, Inc. 26

CONNECTION: Measuring blood pressure can reveal cardiovascular problems Hypertension causes the heart to work harder, weakening the heart over time increased plaque formation from tiny ruptures increased risk of blood clot formation. Hypertension can contribute to heart attacks, strokes, and/or kidney failure. Teaching Tips Students may not relate the structure of the walls of arteries to blood pressure. Consider noting the presence of smooth muscle in the walls of arteries (Figure 23.7C). If these muscles contract, they narrow the arteries and increase pressure. © 2012 Pearson Education, Inc. 27

Smooth muscle controls the distribution of blood Blood flow through capillaries is restricted by precapillary sphincters. By opening and closing these precapillary sphincters, blood flow to particular regions can be increased or decreased. Only about 5–10% of capillaries are open at one time. Teaching Tips Students might wonder why they are discouraged from swimming soon after eating a meal. Blood flow during exercise involves the diversion of blood away from the gut and to major muscle groups likely involved in swimming. This can lead to indigestion or muscle cramping. However, the greatest risk of swimming with a full stomach is more likely that even a small amount of vomit could clog an air passageway. © 2012 Pearson Education, Inc. 28

Precapillary sphincters Thoroughfare channel Figure 23.10 Precapillary sphincters Thoroughfare channel Arteriole Venule Capillaries 1 Sphincters are relaxed. Thoroughfare channel Figure 23.10 The control of capillary blood flow by precapillary sphincters Arteriole Venule 2 Sphincters are contracted. 29

Exchange of materials between blood and interstitial fluid occurs at capillaries Substances leave blood and enter interstitial fluid by diffusion (following concentration gradient) and pressure-driven flow through clefts between epithelial cells. Blood pressure forces fluid (water) out of capillaries at the arterial end. Osmotic pressure draws in fluid (water) at the venous end. Teaching Tips 1. Figure 23.11B depicts the movements of fluid out of and back into capillaries because of changes in osmotic pressure. The text references Module 24.3 for further discussion of the role of the lymphatic system in fluid removal. If you do not plan on addressing Chapter 24, consider including the role of lymphatic vessels in your discussion of Chapter 23. 2. Students who have little practice interpreting electron micrographs might benefit from a closer analysis of Figure 23.11A, in which an electron micrograph is paired with explanatory figure. For example, simply recognizing nuclei in micrographs can be an important starting point in interpreting cellular details and gaining a sense of scale. © 2012 Pearson Education, Inc. 30

Nucleus of epithelial cell Figure 23.11A Interstitial fluid Capillary wall Capillary lumen Nucleus of epithelial cell Clefts between the cells Figure 23.11A A capillary in cross section Muscle cell 31

LE 42-14 Tissue cell INTERSTITIAL FLUID Net fluid movement out movement in Capillary Capillary Red blood cell 15 µm Direction of blood flow Blood pressure Osmotic pressure Inward flow Pressure Outward flow Arterial end of capillary Venous end

Glucose, O2, and other nutrients have greatest concentration in blood at arterial end so they move out by diffusion Water moves by net effect of blood versus osmotic pressure CO2 and other wastes have greatest concentration in interstitial fluid at venous end so they move in by diffusion

STRUCTURE AND FUNCTION OF BLOOD STRUCTURE AND FUNCTION OF BLOOD © 2012 Pearson Education, Inc. 34

Blood consists of red and white blood cells suspended in plasma Plasma (55%) Cellular elements (45%) Constituent Major functions Cell type Number per L (mm3) of blood) Functions Water Solvent for carrying other substances Centrifuged blood sample Red blood cells (erythrocytes) 5–6 million Transport of O2 and some CO2 Ions (blood electrolytes) Osmotic balance, pH buffering, and maintaining ion concentration of interstitial fluid Sodium Potassium Calcium Magnesium Chloride Bicarbonate White blood cells (leukocytes) 5,000–10,000 Defense and immunity Plasma proteins Student Misconceptions and Concerns 1. Students with limited backgrounds in anatomy and physiology might not appreciate the diverse functions of plasma, instead thinking of blood as a transporter of oxygen and carbon dioxide. Figure 23.12 lists the many functions performed by plasma. 2. Students might have heard about blood thinners, thinking that somehow these substances make blood more fluid (like watering down syrup). The term actually refers to substances that make blood clotting less likely. Anticoagulants are specifically addressed in Module 23.14. Teaching Tips 1. If you have a small fiber-optic lamp available, shining the light through your fingertips in a darkened room creates a red glow. This provides a dramatic example of the abundance of hemoglobin in red blood cells in the capillaries of our bodies. 2. Discuss the relationship between the structure and functions of erythrocytes. In Module 23.12, the authors note that the absence of a nucleus permits these cells to carry a greater amount of hemoglobin. But why is an erythrocyte dented in the middle? Wouldn’t it seem more likely to be shaped like a hockey puck? The indentation in the center of an erythrocyte might increase its flexibility, permitting easier passage through small capillaries. Encourage students to contribute other ideas on the adaptive advantages of this unique shape (including a higher surface-to-volume ratio). 3. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, search the American Heart Association website at www.heart.org using the key word aspirin. Osmotic balance and pH buffering Basophils Lymphocytes Fibrinogen Clotting Eosinophils Immunoglobulins (antibodies) Defense Substances transported by blood Neutrophils Monocytes Nutrients (e.g., glucose, fatty acids, vitamins) Waste products of metabolism Respiratory gases (O2 and CO2) Hormones Platelets 250,000– 400,000 Blood clotting 35

Figure 23.13 Figure 23.13 Human red blood cells 36

RED AND WHITE BLOOD CELLS BLOOD HISTOLOGY

New Blood Cells are generated in bone marrow from stem cells Multipotent stem cells are unspecialized and replace themselves throughout the life of an organism. Multipotent stem cells can differentiate into two main types of stem cells. Lymphoid stem cells can in turn produce two types of lymphocytes (T- and B-cells), which function in the immune system. Myeloid stem cells can differentiate into erythrocytes (RBC) other white blood cells platelets Student Misconceptions and Concerns Students might have heard about blood thinners, thinking that somehow these substances make blood more fluid (like watering down syrup). The term actually refers to substances that make blood clotting less likely. Anticoagulants are specifically addressed in Module 23.14. Teaching Tips 1. Advances in stem cell research continue, along with political controversy over whether or not such research should be funded by the federal government. You may want to consider bringing recent articles about stem cell research to class, or encourage your students to find a recent article about some aspect of stem cells and email it to you. 2. You might note that one of the effects of aspirin is to block platelet aggregation. For additional details about the use of aspirin to prevent and treat heart disease, search the American Heart Association website at www.heart.org using the key word aspirin. © 2012 Pearson Education, Inc. 38

Multipotent stem cells (in bone marrow) Figure 23.15 Multipotent stem cells (in bone marrow) Lymphoid stem cells Myeloid stem cells Basophils Erythrocytes Figure 23.15 Differentiation of blood cells from stem cells Platelets Eosinophils Lymphocytes Monocytes Neutrophils 39

Cardiovascular Lab © 2012 Pearson Education, Inc. 40

Pulse Pulse – pressure wave of blood Monitored at “pressure points” where pulse is easily palpated

Blood Pressure Measurements by health professionals are made on the pressure in large arteries Systolic – pressure at the peak of ventricular contraction Diastolic – pressure when ventricles relax Pressure in blood vessels decreases as the distance away from the heart increases

Measuring Arterial Blood Pressure http://www.sumanasinc.com/webcontent/animations/content/bloodpressure.html