Transcript Heart
1 Lecture 11 Outline (Ch. 42) I. II. III. IV. V. Circulatory Systems Human Heart Blood & Vessels Cardiovascular disorders Methods – bulk flow vs. diffusion VII. Gas exchange and partial pressures VIII. Breathing mechanisms IX. Preparation for next lecture 2 Circulation Overview Circulation carries energy, dissolved gasses, wastes • • Connects individual cells in distant parts of body Requirements – Blood – fluid for transport – Blood vessels – channels for transport – Heart – pump for circulation 3 Circulation Overview Circulatory systems are open or closed • • Open- bathes organs in a hemocoel Closed- direct vessel connections to organs Heart Hemolymph in sinuses surrounding organs Pores Heart Blood Interstitial fluid Small branch vessels In each organ Dorsal vessel (main heart) Tubular heart (a) An open circulatory system Auxiliary hearts Ventral vessels (b) A closed circulatory system 4 Circulation Overview Vertebrates have a closed circulatory system • • More efficient – Blood is 5 – 10% of body volume – Flow is more rapid, pressure is higher Multifunctional – Transport dissolved gasses – Distribute nutrients & hormones – Transport waste – Thermoregulation – Circulate immunodefenses Arteries – away from heart, Veins – toward heart 5 The Vertebrate Heart • Artery Heart: Atrium (A) Ventricle (V) Gill capillaries • • Atria collect blood Ventricles send blood through body • The heart has evolved Vein Body capillaries Key Oxygen-rich blood Oxygen-poor blood Bony fishes, rays, sharks Set of muscular chambers Ventricle gill capillaries: gas exchange Blood collects - body capillaries gas exchange Blood returns to heart, swimming helps Single circulation 6 The Vertebrate Heart Pulmonary circuit 2 atria empty into 2 ventricles Lung capillaries Complete septum (this varies) – right side receives oxygen poor blood from body – sends to lungs Endotherms need to deliver 10X as much dissolved gasses and nutrients/waste as same size ectotherms! Double circulation – pulmonary circuit and systemic circuit A V Right A V Left Systemic capillaries Key Systemic circuit Oxygen-rich blood Oxygen-poor blood Amphibians, reptiles, mammals 7 4-chambered heart: A closer look Heart Pulmonary artery • 2 pumps • Right: deoxygenated blood Left: oxygenated blood • Aorta Pulmonary artery Right atrium Left atrium Semilunar valve Semilunar valve Atrioventricular valve Atrioventricular valve Right Left ventricle ventricle 8 Heart • Right atrium receives deO2 blood from veins – Superior vena cava – Inferior vena cava Right ventricle pumps deO2 blood to lungs through pulmonary arteries Pumps into right ventricle 9 Heart • Oxygenated blood returns to left atrium from lungs via pulmonary veins Oxygenated blood pumped to body through aorta Pumps into left ventricle 10 Heart Keeping blood moving • • • Heart valves maintain one-way flow Atrioventricular valves – Between atria & ventricles Semilunar valves – Between ventricles & arteries 11 Heart 2 Atrial systole and ventricular diastole The Cardiac Cycle 1 Atrial and ventricular diastole 0.1 sec 0.4 sec 0.3 sec 3 Ventricular systole and atrial diastole 12 Heart The Cardiac Cycle & Blood Pressure Normal blood pressure ~120/70 • • Systolic – Ventricular contractions (higher pressure) Diastolic – Period between contractions (lower pressure) sphygmomanometer • “Lub-dup” sounds heard with stethoscope – Lub – blood against closed AV valves – Dup – blood against closed semilunar valves 13 Heart Cardiac muscle contracts • Present only in the heart Cells linked by intercalated discs Prevents strong contractions from tearing muscle Allows rapid spread of electrical signal for simultaneous regional contraction 14 Heart Keeping blood moving • • • Pacemaker cells initiate and coordinate contractions Sinoatrial (SA) node – Primary pacemaker – Stimulates atrial contractions Atrioventricular (AV) node – Delayed impulse received from SA node – Ventricular contraction after atrial contractions have filled them with blood (delay ~0.1 sec) 15 Blood Plasma • • Primarily water Dissolved proteins and electrolytes Blood • • Plasma fluid Cells – Red blood cells – transport – White blood cells – defense – Platelets – clotting 16 Blood Red blood cells: Erythrocytes • • • Most abundant blood cells (over 99%) Transport O2 and CO2 Iron-based hemoglobin protein binds to O2 and transports from areas of high concentration to low concentration 17 Blood Erythrocytes are short-lived • • • • Formed in bone marrow Lack nuclei (cannot divide or make proteins) Dead cells are removed by liver and spleen – Iron is recycled, although some is excreted Number of erythrocytes maintained by negative feedback 18 Blood White blood cells: leukocytes • • Less than 1% of blood cells Disease defense – – – – – Consume foreign particles (macrophages) Produce antibodies (lymphocytes) 19 Blood Platelets • • • Cellular fragments aid blood clotting Ruptured cells and platelets work together to produce substances that plug damaged vessels Scabs are platelets embedded in web of fibrin proteins 20 Blood is carried in vessels 21 Artery Vein SEM Valve 100 µm Basal lamina Endothelium Smooth muscle Connective tissue Endothelium Smooth muscle Capillary Connective tissue Artery Vein Capillary 15 µm Red blood cell Venule LM Arteriole 22 Blood Vessels Arteries Arterioles Arteries • Carry blood away from heart • Thick-walled: Heart Capillaries • Smooth muscle/elastic fibers • Withstand high pressure Veins Venules 23 Blood Vessels Arteries Arterioles Arterioles • Control distribution of blood flow • Smooth muscle expands / contracts • Under hormone / NS control Capillaries Heart Veins Venules 24 Blood Vessels • • • • Arterioles Contract walls: redirects blood to heart and muscles when needed (stress, exercise, cold) Relax walls: brings more blood to skin capillaries to dissipate excess heat Precapillary sphincters control blood flow to capillaries 25 Blood Vessels Arteries Arterioles Capillaries • Nutrients/waste exchanged with cells: • Vessel wall one-cell thick • Blood flow very slow Capillaries Heart • Materials exit/enter via diffusion Veins Venules 26 Blood Vessels Arteries Arterioles Venules & Veins • Carry blood towards the heart Heart Capillaries • Thin-walled; large diameter • One-way to prevent backflow Veins Venules 27 Blood Vessels Skeletal Muscle Pump: Vein Valve: 28 Blood Vessels Varicose veins occur if the vein valves become inefficient 29 Blood Vessels Cardiovascular Disorders: • Leading cause of death in the United States 1) Hypertension = High blood pressure • Resistance in vessels = work for heart 2) Atherosclerosis = Deposits (plaques) collect in vessels Connective tissue Smooth muscle Endothelium Plaque 30 (a) Normal artery 50 µm (b) Partly clogged artery 250 µm Thought Question: If you are an athlete who trains at high elevations, what happens if you compete at a lower elevation? 31 Overview Living things process energy • They need oxygen for this - Why? 32 Gas Exchange Systems Respiratory systems enable gas exchange • Bulk flow – Movement in bulk – Air/water to respiratory surface – Blood through vessels • Diffusion – Individual molecules move down concentration gradients – Gas exchange across respiratory surface – Gas exchange in tissues 33 Gas Exchange Systems • Aquatic gas exchange Gills • Elaborately folded ( surface area) • Contain capillary beds • Gill size inversely related to [O2] • Large gills = low [O2] 34 Gas Exchange Systems • Dissolved O2 is < 1% of water (21% of air) • Countercurrent exchange increases efficiency Fish Efficiency 35 Gas Exchange Systems Reptiles & Mammals use lungs exclusively • • Lack permeable skin Lungs are more efficient – Especially birds! 36 Mammals Human Respiration • • • Air enters through nose and mouth to pharynx Travels through larynx (voice box) Epiglottis directs travel Nasal cavity Pharynx Left lung Larynx (Esophagus) Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) 37 Human Respiration On to the lungs • • • • • • • Trachea Bronchi Bronchioles Alveoli Air is warmed & cleaned • • Dust & bacteria trapped by mucus Swept up and out by cilia Branch of pulmonary vein provide enormous surface area Surfactant keeps surface moist Association with capillaries – Diffusion of gasses Branch of pulmonary artery Terminal bronchiole Alveoli Capillaries 38 Human Respiration • Gas exchange is driven by differences in pressures • Blood from body with low O2, has a partial oxygen pressure (PO2) of ~40 mm Hg • By contrast, the PO2 in the alveoli is about 100 mm Hg • Blood leaving lungs, thus, normally contains a PO2 of ~100 mm 1 Inhaled air 8 Exhaled air Alveolar epithelial cells 2 Alveolar spaces CO2 O2 Alveolar capillaries 7 Pulmonary arteries 3 Pulmonary veins 6 Systemic veins 4 Systemic arteries Heart CO2 O2 Systemic capillaries 5 Body tissue 39 Transport of gasses CO2 Transport • • • CO2 binds hemoglobin loosely Dissolved in plasma Combines with H20 to form bicarbonate (HCO3-) – More CO2 = lower pH The Bohr Effect: Hemoglobin binds more tightly to O2 when pH is increased and loosely when pH is decreased 40 Transport of gasses O2 Transport • Binds to hemoglobin – Removes O2 from plasma solution – Increases concentration gradient; favors diffusion from air via alveoli CO binds more tightly to hemoglobin than O2 Prevents O2 transport 41 Breathing Mechanisms • Inhalation: Rib muscles 1 contract to cage expand rib Rib expands. cage Diaphragm contracts (down) expands the volume of thorax and lungs 2 Air inhaled. Rib cage gets smaller. Air exhaled. Lung Diaphragm • Thoracic cavity expands, produces negative pressure which draws air into the lungs 42 Breathing Mechanisms Breathing is involuntary • • Homeostasis: Blood pH of about 7.4 CO2 level decreases. Controlled by respiratory center of the brain Adjusts breath rate & volume based on sensory input – Maintain a constant concentration of CO2 Response: Rib muscles and diaphragm increase rate and depth of ventilation. Stimulus: Rising level of CO2 in tissues lowers blood pH. Carotid arteries Sensor/control center: Cerebrospinal fluid Aorta Medulla oblongata 43 Things To Do After Lecture 11… Reading and Preparation: 1. Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. 2. Ch. 42 Self-Quiz: #2, 3, 4, 6, 7 (correct answers in back of book) 3. Read chapter 42, focus on material covered in lecture (terms, concepts, and figures!) 4. Skim next lecture. “HOMEWORK” (NOT COLLECTED – but things to think about for studying): 1. Compare and contrast veins and arteries in terms of structure and function. 2. Diagram the path blood takes from the body, to the heart and lungs, back to the body. 3. Explain in detail how oxygen is carried in the bloodstream and exchanged in the lungs and at cells, from drawing a breath to bulk flow in blood to diffusion at cells. What do cells use this oxygen for? 4. Explain homeostatic control of breathing.