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Chapter 23 Circulation PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko 23.1 - 23.5 INTRO TO CIRCULATORY SYSTEMS © 2012 Pearson Education, Inc. 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. © 2012 Pearson Education, Inc. Simple Gastrovascular Cavity is Found in Cnidarians and Flatworms 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. © 2012 Pearson Education, Inc. Cnidarians = jellyfish and hydra Notice only one opening in/out! polyp medusa Flatworms - We’re so flat because we exchange materials directly with environment. Only ONE entrance/exit! YIKES!! Gastrovascular cavity Nerve cords Mouth/Anus Eyecups Nervous tissue clusters © 2012 Pearson Education, Inc. Bilateral symmetry Small organisms have sufficient SA:volume ratio that they do not require a specialized circulatory system. Diffusion Mouth Gastrovascular cavity Diffusion Diffusion Single cell Two cell layers 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. © 2012 Pearson Education, Inc. EXTERNAL ENVIRONMENT CO2 O2 Food Mouth ANIMAL Respiratory system Digestive system Interstitial fluid Heart Nutrients Circulatory system Body cells Urinary system Intestine Anus Unabsorbed matter (feces) Metabolic waste products (urine) But large, complex organisms require true CV system to maintain sufficient SA:volume ratio 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. Pores © 2012 Pearson Education, Inc. Tubular heart 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. © 2012 Pearson Education, Inc. Three Types of Blood Vessels Found in CV Systems 1. Arteries carry blood away from the heart. 2. Veins return blood to the heart. Capillary beds Artery (O2-rich blood) Arteriole 3. Capillaries convey blood between arteries and veins. Venule Vein Gill capillaries © 2012 Pearson Education, Inc. Atrium Artery (O2-poor blood) Ventricle Heart 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. © 2012 Pearson Education, Inc. Figure 23.2A Gill capillaries Heart: Ventricle Atrium Body capillaries Double circulation 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. © 2012 Pearson Education, Inc. Figure 23.2B Lung and skin capillaries Pulmocutaneous circuit Atrium Atrium Ventricle Left Right Systemic circuit Systemic capillaries 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. © 2012 Pearson Education, Inc. Figure 23.2C Lung capillaries Pulmonary circuit Atrium Atrium Ventricle Ventricle Right Left Systemic circuit Systemic capillaries THE HUMAN CARDIOVASCULAR SYSTEM AND HEART © 2012 Pearson Education, Inc. 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. Animation: Path of Blood Flow in Mammals © 2012 Pearson Education, Inc. Figure 23.3A 8 Capillaries of head, chest and arms Superior vena cava Pulmonary artery Pulmonary artery Aorta 9 Capillaries of right lung 2 7 Capillaries of left lung 2 3 3 5 4 10 4 Pulmonary vein 6 1 Right atrium 9 Pulmonary vein Left atrium Left ventricle Right ventricle Aorta Inferior vena cava 8 Capillaries of abdominal region and legs 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 The Cardiac Cycle The repeated contraction and relaxation of pumping blood is called the cardiac cycle. The cycle consists of two main phases. 1. During diastole, heart relaxes and all chambers fill with blood 2. During systole, heart contracts and blood flows – from atria into ventricles – Then from ventricles into arteries © 2012 Pearson Education, Inc. Figure 23.4_s1 Diastole 1 The heart is relaxed. The semilunar valves are closed. All chambers fill with blood 0.4 sec The AV valves are open. Figure 23.4_s2 Systole Diastole 1 The heart is relaxed. The semilunar valves are closed. 2 The atria contract. Pushes blood into ventricles 0.1 sec 0.4 sec The AV valves are open. Figure 23.4_s3 Systole Diastole 1 The heart is relaxed. The semilunar valves are closed. 2 The atria contract. 0.1 sec 3 The ventricles contract. 0.4 sec 0.3 sec The AV valves are open. The AV valves are closed. Ventricles pump Blood out thru arteries 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 © 2012 Pearson Education, Inc. 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. © 2012 Pearson Education, Inc. 1 Signals from the SA node spread through the atria. SA node (pacemaker) Right atrium ECG