Lecture 14 Outline (Ch. 42) I. Circulatory Systems II.Human Heart III. Blood & Vessels IV.Cardiovascular disorders V.Methods – bulk flow vs. diffusion VII.Gas exchange and partial pressures VIII.Breathing mechanisms IX. Summary

2 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 Circulation Overview

3 Circulatory systems are open or closed Open- bathes organs in hemolymph Closed- direct vessel connections to organs Circulation Overview Heart Hemolymph in sinuses surrounding organs Heart Interstitial fluid Small branch vessels In each organ Blood Dorsal vessel (main heart) Auxiliary heartsVentral vessels (b) A closed circulatory system (a) An open circulatory system Tubular heart Pores

4 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 Circulation Overview Arteries – away from heart, Veins – toward heart

5 Set of muscular chambers Atria collect blood Ventricles send blood through body The heart has evolved The Vertebrate Heart Ventricle  gill capillaries: gas exchange Blood collects - body capillaries  gas exchange Blood returns to heart, swimming helps Single circulation Artery Heart: Atrium (A) Ventricle (V) Vein Gill capillaries Body capillaries Key Oxygen-rich blood Oxygen-poor blood Bony fishes, rays, sharks

6 The Vertebrate Heart 2 atria empty into 2 ventricles 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! Systemic circuit Systemic capillaries RightLeft A A VV Lung capillaries Pulmonary circuit Key Oxygen-rich blood Oxygen-poor blood Amphibians, reptiles, mammals Double circulation – pulmonary circuit and systemic circuit

7 4-chambered heart: A closer look 2 pumps Right: deoxygenated blood Left: oxygenated blood Heart Pulmonary artery Right atrium Semilunar valve Atrioventricular valve Right ventricle Left ventricle Atrioventricular valve Semilunar valve Left atrium Pulmonary artery Aorta

8 Right ventricle pumps deO 2 blood to lungs through pulmonary arteries Pumps into right ventricle Heart Right atrium receives deO 2 blood from veins – Superior vena cava – Inferior vena cava

9 Oxygenated blood returns to left atrium from lungs via pulmonary veins Oxygenated blood pumped to body through aorta Pumps into left ventricle Heart

10 Keeping blood moving Heart valves maintain one-way flow Atrioventricular valves – Between atria & ventricles Semilunar valves – Between ventricles & arteries Heart

For each term, determine whether the region contains oxygenated or deoxygenated blood: AortaPulmonary veins Inferior vena cavaRight atrium Left atriumRight ventricle Left ventricleSuperior vena cava Pulmonary arteries OxygenatedDeoxygenated

12 The Cardiac Cycle & Blood Pressure Heart Normal blood pressure ~120/70 “Lub-dup” sounds heard with stethoscope –Lub – blood against closed AV valves –Dup – blood against closed semilunar valves Systolic – Ventricular contractions (higher pressure) Diastolic – Period between contractions (lower pressure) sphygmomanometer

13 The Cardiac Cycle Heart Atrial and ventricular diastole 0.4 sec 1 Atrial systole and ventricular diastole 0.1 sec 2 Ventricular systole and atrial diastole 0.3 sec 3

14 Cardiac muscle contracts Present only in the heart Heart Cells linked by intercalated discs Prevents strong contractions from tearing muscle Allows rapid spread of electrical signal for simultaneous regional contraction

15 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) Heart

What’s in blood?

17 Red blood cells: Erythrocytes Most abundant blood cells (over 99%) Transport O 2 and CO 2 Iron-based hemoglobin protein binds to O 2 and transports from areas of high concentration to low concentration Blood

18 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 Blood

19 White blood cells: leukocytes Less than 1% of blood cells Disease defense – Consume foreign – particles – (macrophages) – Produce antibodies – (lymphocytes) Blood

20 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 Blood

21 ArteryVein SEM 100 µm Endothelium Artery Smooth muscle Connective tissue Capillary Basal lamina Endothelium Smooth muscle Connective tissue Valve Vein Arteriole Venule Red blood cell Capillary 15 µm LM Blood is carried in vessels!

22 Heart ArteriesArterioles CapillariesVenules Veins Carry blood away from heart Thick-walled: Smooth muscle/elastic fibers Withstand high pressure Arteries Blood Vessels

23 Heart ArteriesArterioles CapillariesVenules Veins Control distribution of blood flow Smooth muscle expands / contracts Under hormone / NS control Arterioles Blood Vessels

24 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 Blood Vessels

25 Heart ArteriesArterioles CapillariesVenules Veins Nutrients/waste exchanged with cells: Vessel wall one-cell thick Blood flow very slow Materials exit/enter via diffusion Capillaries Blood Vessels

26 Heart ArteriesArterioles CapillariesVenules Veins Carry blood towards the heart Thin-walled; large diameter One-way to prevent backflow Venules & Veins Blood Vessels

27 Skeletal Muscle Pump: Vein Valve: Blood Vessels

28 Blood Vessels Varicose veins occur if the vein valves become inefficient

29 Cardiovascular Disorders: Leading cause of death in the United States 1) Hypertension = High blood pressure  Resistance in vessels =  work for heart Blood Vessels 2) Atherosclerosis = Deposits (plaques) collect in vessels Connective tissue Smooth muscle Endothelium Plaque (a) Normal artery(b) Partly clogged artery 50 µm 250 µm

30 If you are an athlete who trains at high elevations, what happens if you compete at a lower elevation? Thought Question:

31 Living things process energy They need oxygen for this - Why? Overview

32 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 Gas Exchange Systems

33 Gills Aquatic gas exchange Gas Exchange Systems Elaborately folded (  surface area) Contain capillary beds Gill size inversely related to [O 2 ] Large gills = low [O 2 ]

34 Gas Exchange Systems Fish Efficiency Dissolved O 2 is < 1% of water (21% of air) Countercurrent exchange increases efficiency

35 Reptiles & Mammals use lungs exclusively Lack permeable skin Lungs are more efficient – Especially birds! Gas Exchange Systems

36 Human Respiration Air enters through nose and mouth to pharynx Travels through larynx (voice box) Epiglottis directs travel Mammals Pharynx Larynx (Esophagus) Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) Left lung Nasal cavity

37 On to the lungs Trachea  Bronchi  Bronchioles  Alveoli Human Respiration Air is warmed & cleaned Dust & bacteria trapped by mucus Swept up and out by cilia provide enormous surface area Surfactant keeps surface moist Association with capillaries –Diffusion of gasses Capillaries Alveoli Branch of pulmonary artery Branch of pulmonary vein Terminal bronchiole

Both mammals and reptiles must maintain homeostasis and use aerobic respiration. A.Would you expect the lungs of a lizard (ectotherm) to have more or fewer alveoli per unit area than lungs of a rat (endotherm)? Explain why. B.Would you expect the heart rate of the lizard to be higher or lower than the heart rate of the rat? Explain.

39 Human Respiration Gas exchange is driven by differences in pressures Blood from body with low O 2, has a partial oxygen pressure (P O2 ) of ~40 mm Hg By contrast, the P O2 in the alveoli is about 100 mm Hg Blood leaving lungs, thus, normally contains a P O2 of ~100 mm Exhaled air Inhaled air Pulmonary arteries Systemic veins Systemic arteries Pulmonary veins Alveolar capillaries Alveolar spaces Alveolar epithelial cells Heart Systemic capillaries CO 2 O2O2 Body tissue CO 2 O2O

40 CO 2 Transport CO 2 binds hemoglobin loosely Dissolved in plasma Combines with H 2 0 to form bicarbonate (HCO 3 - ) – More CO 2 = lower pH Transport of gasses The Bohr Effect: Hemoglobin binds more tightly to O 2 when pH is increased and loosely when pH is decreased

41 O 2 Transport Binds to hemoglobin – Removes O 2 from plasma solution – Increases concentration gradient; favors diffusion from air via alveoli Transport of gasses CO binds more tightly to hemoglobin than O 2 Prevents O 2 transport

42 Breathing Mechanisms Inhalation: Rib muscles contract to expand rib cage Diaphragm contracts (down) expands the volume of thorax and lungs Thoracic cavity expands, produces negative pressure which draws air into the lungs Rib cage expands. Air inhaled. Air exhaled. Rib cage gets smaller. 12 Lung Diaphragm

43 Breathing is involuntary Controlled by respiratory center of the brain Adjusts breath rate & volume based on sensory input – Maintain a constant concentration of CO 2 Breathing Mechanisms Homeostasis: Blood pH of about 7.4 CO 2 level decreases. Stimulus: Rising level of CO 2 in tissues lowers blood pH. Response: Rib muscles and diaphragm increase rate and depth of ventilation. Carotid arteries Aorta Sensor/control center: Cerebrospinal fluid Medulla oblongata