Ch. 42 Circulation and Gas Exchange

1. Ch. 42 Circulation and Gas Exchange LO 2.25 The student can construct explanations based on scientific evidence that homeostatic mechanisms reflect continuity due to common ancestry and/or divergence due toadaptation in different environments. LO 2.27 The student is able to connect differences in the environment with the evolution of homeostatic mechanisms. LO 4.8 The student is able to evaluate scientific questions concerning organisms that exhibit complex properties due to the interaction of their constituent parts. LO 4.9 The student is able to predict the effects of a change in a component(s) of a biological system on the functionality of an organism(s). LO 4.10 The student is able to refine representations and models to illustrate biocomplexity due to interactions of the constituent parts.

2. 42.1 Circulatory Systems Link Exchange Surfaces with Cells Throughout the Body • Every cell in your body needs resources (O2 and Glucose) and needs to get rid of wastes (CO2 and Ammonia). • All cells need to be in contact with the environment. • Gastrovascular cavities containing nutrients and wastes bath all the cells of the organism. Mouth Circular canal Gastrovascular cavity Mouth Pharynx Radial canals 2 mm 5 cm (a) The moon jelly Aurelia, a cnidarian (b) The planarian Dugesia, a flatworm

3. Circulatory system – fluid, interconnecting vessels, and a muscular pump (heart) • Open– circulatory fluid (hemolymph) bathes the organs. • Fluid is released around organs when the heart contracts, and floods back into vessels with valves when the heart relaxes. • EX: arthropods and molluscs • Closed– circulatory fluid (blood) stays confined to vessels. • Blood travel out of heart’s ventricle (lower chambers) in arteries, back to heart’s atria (upper chambers) in veins, and exchanges materials with cells in capillaries. • EX: annelids, cephalopods, and all vertebrates (a) An open circulatory system (b) A closed circulatory system Heart Heart Interstitial fluid Blood Hemolymph in sinuses surrounding organs Small branch vessels in each organ Pores Dorsal vessel (main heart) Auxiliary hearts Ventral vessels Tubular heart

4. (a) Single circulation Single Circulation Gill capillaries • Bony fish, rays and sharks • 2 chambers (1 atrium, 1 ventricle) • Blood flows through the heard only once. • A  V  artery  gills  body  vein Artery Heart: Atrium (A) Ventricle (V) Vein Body capillaries Key Oxygen-rich blood Oxygen-poor blood

5. Double Circulation Mammals and Birds Amphibians Reptiles (Except Birds) • Amphibians, reptiles, mammals and birds. • Blood goes to the heart twice, through 2 circulations. • Pulmonary circuit – blood travels from (right) heart to gas exchange tissue • Systemic circuit – blood travel from (left) heart to the body cells Pulmonary circuit Pulmonary circuit Pulmocutaneous circuit Lung capillaries Lung and skin capillaries Lung capillaries Right systemic aorta Left systemic aorta Atrium (A) Atrium (A) A A A A Incomplete septum Incomplete septum V V V V Right Left Right Left Left Right Ventricle (V) Systemic capillaries Systemic capillaries Systemic capillaries Systemic circuit Systemic circuit Systemic circuit Key Oxygen-rich blood Oxygen-poor blood

6. Superior vena cava Capillaries of head and forelimbs Aorta Pulmonary artery 42.2 Coordinated Cycles of Heart Contraction Drive Double Circulation in Mammals Pulmonary artery Pulmonary artery Pulmonary artery Right atrium Capillaries of right lung Capillaries of left lung Aorta Left atrium Semilunar valve Pulmonary vein Semilunar valve Pulmonary vein Left atrium Right atrium Left ventricle Right ventricle Atrioventricular valve Atrioventricular valve Aorta Inferior vena cava Capillaries of abdominal organs and hind limbs Right ventricle Left ventricle

7. Atrial and Atrial systole and ventricular Ventricular systole and atrial ventricular diastole diastole diastole 2 The Mammalian Heart • Contraction phase heart is called systole. • The relaxation phase is called diastole. • Average cardiac output is 5L/min at a heart rate of 72 beats/min. • The “lub-dub” sound is the sound of blood recoiling against closed atrioventricular valves and semilunar valves (respectively). • A heart murmur occurs when the valves don’t fully close, causing blood to backflow. 1 0.1 sec 0.3 sec 0.4 sec 3

8. Maintaining the Heart’s Rhythmic Beat • Sinoatrial (SA) node in the right atrium coordinates the contraction of the other heart cells (pacemaker). • This impulse can be seen on an electrocardiogram (ECG) • Atrioventricular (AV) node delays the impulse to the ventricles then sends it to have both contract at the same time. • Controlled by sympathetic (quickens) and parasympathetic (slows) nervous system. 1 2 3 4 AV node SA node (pacemaker) Bundle branches Purkinje fibers Heart apex ECG R T P Q S

9. Blood Pressure • A beating heart generates high blood pressure, causing blood to flow from the heart to the arteries. • Ventricular contraction causes systolic pressure. • Elastic connective tissues expand and recoil to maintain blood pressure away from the heart once the ventricle relaxes (diastolic pressure). • Vasoconstriction • Increases blood pressure due to artery walls constricting • Caused by physical or emotional stress resulting in nervous and hormonal response to release endothelin to smooth muscle. • Vasodilation • Decreases blood pressure due to artery walls opening up (dilating) • Caused by environmental or physical cues to release nitric oxide (NO).

10. Blood Pressure and Gravity Blood pressure reading: 120/70 1 3 2 • Measured at same height as heart. • Standing decreases blood pressure to the brain because it is further from the heart and working harder against gravity. • Apply to long necked organisms (giraffes) – need valves to slow blood flow when the neck is bend over to take a drink. 120 120 70 Artery closed Sounds audible in stethoscope Sounds stop

11. Capillary Function • Capillaries are the sight of exchange with the interstitial fluid. • Some molecules move via endo- and exocytosis. • Some molecules (O2 and CO2) can diffuse across the endothelium. • Blood pressure tends to drive fluid out of the capillaries. • Proteins dispersed in the blood tend to drive fluid into the capillaries (osmotic pressure) • Blood pressure is typically greater than osmotic pressure, particularly close to the arteriole. Body cell INTERSTITIAL FLUID Net fluid movement out Blood pressure Osmotic pressure Arterial end of capillary Venous end of capillary Direction of blood flow

12. Fluid Return by the Lymphatic System • The lymphatic system is a network of vessels and nodes that returns fluids, proteins and cells to the circulatory system. • Lymph is the fluid lost by the capillaries. • Vessels work similarly to veins (valves and muscle contractions) • Lymph nodes filter lymph and house cells that attach pathogens (immune system). • Found in the neck, armpits, and groin. • Honeycomb of white blood cells that quickly divide when the body is infected. • This causes them to swell and is why they are checked by doctors.

13. 42.4 Blood Components Function in Exchange, Transport, and Defense Plasma 55% Cellular elements 45% Number per L (mm3) of blood Constituent Major functions Cell type Functions Blood Composition Water Solvent for carrying other substances Leukocytes (white blood cells) 5,000–10,000 Defense and immunity Ions (blood electrolytes) Separated blood elements Osmotic balance, pH buffering, and regulation of membrane permeability Lymphocytes Basophils Sodium Potassium Calcium Magnesium Chloride Bicarbonate Eosinophils Monocytes Plasma proteins Neutrophils Osmotic balance, pH buffering Albumin Platelets 250,000–400,000 Blood clotting Fibrinogen Clotting Immunoglobulins (antibodies) Defense Erythrocytes (red blood cells) 5–6 million Transport of O2 and some CO2 Substances transported by blood Nutrients Waste products Respiratory gases Hormones

14. Blood Clotting Mechanism • Coagulation—solid clot forms from liquid blood • A cascade of complex reactions converts inactive fibrinogen to fibrin, forming a clot • A blood clot formed within a blood vessel is called a thrombus and can block blood flow • Hemophilia—results when a mutation causes a change in any one of the proteins involved in the cascade

15. Lumen of artery Plaque Cardiovascular Disease Endothelium Smooth muscle 1 2 • Atherosclerosis • Hardening of arteries by accumulating of fatty deposits due to high levels of low-density lipoprotein (LPL) • Heart Attacks • Damage or death of cardiac muscle tissue resulting from blockage of one or more coronary arteries. • Strokes • Death of nervous tissue in the brain from ruptured or blocked arteries in the head. Smooth muscle cell LDL Foam cell Extra- cellular matrix Macrophage T lymphocyte Plaque rupture 4 3 Fibrous cap Cholesterol

16. 42.5 Gas Exchange Occurs Across Specialized Respiratory Surfaces • Air is less dense, viscous, and has a higher concentration of O2. • These animals do not need to be very efficient breathers • Water is more dense, viscous, and has a lower concentration of O2. • These animals expend a lot of energy for gas exchange. Respiratory Surfaces • Moist • Large surface area and thin • Sponges, cnidarians, and flatworms have body cells in direct contact with environment (diffusion). • Earthworms and some amphibians use their skin. • Fish use gills • Insects use trachea • Other vertebrates use lungs

17. PO (mm Hg) in blood 2 Gills in Aquatic Animals O2-poor blood Gill arch O2-rich blood • Outfoldings of the body surface that are suspended in the water. • Water must move across gills for gas exchange (ventilation) • Paddle-like appendages that drive a current of water over the gills • Cilia move water over gills • Taking in and ejecting water over gills • Swimming and opening of mouth for water to pass through the pharynx, over the gills, and out of the body. • Countercurrent exchange for diffusion of gases and heat. Lamella Blood vessels Gill arch Water flow Operculum Water flow Blood flow Countercurrent exchange PO (mm Hg) in water 2 150 120 90 60 30 Gill filaments Net diffu- sion of O2 140 110 80 50 20

18. Tracheoles Muscle fiber Mitochondria Tracheal Systems in Insects • Air tubes that run throughout the body. • Tracheae open to the outside which branch into smaller tubes which come close to every cell. • Gas is exchanged by diffusion across the epithelium. 2.5 m Body cell Tracheae Air sac Tracheole Air sacs Trachea Air External opening

19. Lungs Branch of pulmonary vein (oxygen-rich blood) Branch of pulmonary artery (oxygen-poor blood) • Localized organ which needs the circulatory system to go to cells for gas exchange. • Air flows: • Nose/mouth • Pharynx • Larynx (vocal cords) • Epiglottis closes esopohogous • Trachea (windpipe) • 2 bronchi (1 to each lung) • Bronchioles (cilia/mucous trap dirt) • Alveoli (gas exchange) • Leukocytes patrol and keep clean • Smoking can overwhelm Terminal bronchiole Nasal cavity Pharynx Left lung Larynx Alveoli (Esophagus) 50 m Trachea Right lung Capillaries Bronchus Bronchiole Diaphragm (Heart) Dense capillary bed enveloping alveoli (SEM)

20. Anterior air sacs 42.6 Breathing Ventilates the Lungs Posterior air sacs How an Amphibian Breathes • Positive pressure breathing forces (pushes) air down the trachea. • The lungs elastically recoil, forcing air out (exhale) How a Bird Breathes • Air moves in 1 direction across gas exchange surface. • Fresh air doesn’t mix with “old” air. Lungs Airflow Air tubes (parabronchi) in lung 1 mm Lungs Anterior air sacs Posterior air sacs 3 2 4 1 First inhalation Second inhalation 1 3 First exhalation Second exhalation 4 2

21. How a Mammal Breathes 1 2 • Negative pressure breathing pulls air into lungs. • The rib muscles and diaphragm contract, creating a negative pressure in the thoracic cavity. This causes air to rush into the lung (high to low pressure). • When they relax, air is pushes out. • Tidal volume is the average volume of air inhaled whereas vital capacity is the maximum volume. Residual volume is air that is left in the lungs after exhalation. Air inhaled. Air exhaled. Rib cage expands. Rib cage gets smaller. Lung Diaphragm

22. Homeostasis: Blood pH of about 7.4 Control of Breathing CO2 level decreases. • Involuntary action controlled by the medulla oblongata. • Uses pH as an indicator of CO2 concentrations of the surrounding tissues . • CO2 reaction with H2O of CS fluid creating carbonic acid. This dissociates into a bicarbonate ion and H+. Stimulus: Rising level of CO2 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

23. PO (mm Hg) 2 42.7 Adaptations for Gas Exchange Include Pigments that Bind and Transport Gases 100 pH 7.4 80 pH 7.2 • O2 transport proteins bound to a metal; called pigments because they have distinctive colors. • Hemoglobin • 4 polypeptide chains each with a heme group attached to iron. • Can carry up to 4 O2 • When 1 subunit binds to O2the others change shape to become more susceptible to O2. • When pH drops, it releases more O2(Bohr shift). Hemoglobin retains less O2 at lower pH (higher CO2 concentration) 60 O2 saturation of hemoglobin (%) 40 20 Iron 0 0 20 40 60 80 100 Heme Hemoglobin (b) pH and hemoglobin dissociation

24. Body tissue CO2 transport from tissues Carbon Dioxide Transport CO2 produced Interstitial fluid CO2 Plasma within capillary CO2 Capillary wall • CO2 is not directly transported in blood. • It dissociated into bicarbonate and H+ • H+ attaches to hemoglobin • Bicarbinate travels in plasma • In lungs, it recombines to for CO2 again. CO2 H2O Hemoglobin (Hb) picks up CO2 and H+. Red blood cell H2CO3 Hb Carbonic acid H+ HCO3 Bicarbonate  HCO3 To lungs CO2 transport to lungs HCO3 H+ HCO3  Hemoglobin releases CO2 and H+. Hb H2CO3 H2O CO2 CO2 CO2 CO2 Alveolar space in lung

25. Respiratory Adaptations of Diving Mammals • Apneatic mammals • Stores more O2 in blood or attached to myoglobin proteins in muscles for later use. • “Turn off” unnecessary organs and shunt blood away from them.

26. 1 Inhaled air 8 Exhaled air Putting the Two Together 2 Alveolar spaces Alveolar epithelial cells CO2 O2 Alveolar capillaries 7 Pulmonary arteries 3 Pulmonary veins 6 4 Systemic veins Systemic arteries Heart Systemic capillaries CO2 O2 Body tissue 5 (a) The path of respiratory gases in the circulatory system