1. 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 to adaptation 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. Ch. 42 Circulation and Gas Exchange

2. 42.1 Circulatory Systems Link Exchange Surfaces with Cells Throughout the Body Every cell in your body needs resources (O 2 and Glucose) and needs to get rid of wastes (CO 2 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. Circular canal Mouth Radial canals 5 cm (a) The moon jelly Aurelia, a cnidarian (b) The planarian Dugesia, a flatworm Gastrovascular cavity Mouth Pharynx 2 mm

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 Heart Hemolymph in sinuses surrounding organs Pores Tubular heart Dorsal vessel (main heart) Auxiliary hearts Small branch vessels in each organ Ventral vessels Blood Interstitial fluid Heart (b) A closed circulatory system

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

5. Double Circulation 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 AmphibiansReptiles (Except Birds) Pulmocutaneous circuit Pulmonary circuit Lung and skin capillaries Atrium (A) Atrium (A) LeftRight Ventricle (V) Systemic capillaries Systemic circuit Systemic capillaries Incomplete septum Incomplete septum Left systemic aorta LeftRight systemic aorta A A VV Lung capillaries Lung capillaries Pulmonary circuit AA V V Left Right Systemic capillaries Key Oxygen-rich blood Oxygen-poor blood Mammals and Birds

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

7. 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. Atrial and ventricular diastole Atrial systole and ventricular diastole Ventricular systole and atrial diastole 0.1 sec 0.4 sec 0.3 sec 2 1 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. SA node (pacemaker) AV node Bundle branches Heart apex Purkinje fibers ECG 1234 P Q R S T

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 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. Blood pressure reading: 120/70 120 70 Sounds stop Sounds audible in stethoscope 120 Artery closed 1 2 3

11. Capillary Function Capillaries are the sight of exchange with the interstitial fluid. Some molecules move via endo- and exocytosis. Some molecules (O 2 and CO 2 ) 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. INTERSTITIAL FLUID Net fluid movement out Blood pressure Osmotic pressure Arterial end of capillary Direction of blood flow Venous end of capillary Body cell

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 Blood Composition Plasma 55% ConstituentMajor functions Water Ions (blood electrolytes) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Solvent for carrying other substances Osmotic balance, pH buffering, and regulation of membrane permeability Plasma proteins Osmotic balance, pH buffering Albumin Fibrinogen Immunoglobulins (antibodies) Clotting Defense Substances transported by blood Nutrients Waste products Respiratory gases Hormones Separated blood elements Basophils Neutrophils Monocytes Lymphocytes Eosinophils Platelets Erythrocytes (red blood cells) 5–6 million 250,000–400,000Blood clotting Transport of O 2 and some CO 2 Defense and immunity Functions Number per  L (mm 3 ) of blood Cell type Cellular elements 45% Leukocytes (white blood cells)5,000–10,000

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. Cardiovascular Disease 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. Lumen of artery Smooth muscle Endothelium Plaque Smooth muscle cell T lymphocyte Extra- cellular matrix Foam cell Macrophage Plaque rupture LDL Cholesterol Fibrous cap 12 4 3

16. 42.5 Gas Exchange Occurs Across Specialized Respiratory Surfaces Air is less dense, viscous, and has a higher concentration of O 2. These animals do not need to be very efficient breathers Water is more dense, viscous, and has a lower concentration of O 2. 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. Gills in Aquatic Animals 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. Gill arch O 2 -poor blood O 2 -rich blood Blood vessels Gill arch Operculum Water flow Water flow Blood flow Countercurrent exchange P O (mm Hg) in water 2 150 P O (mm Hg) in blood 2 120906030 140110805020 Net diffu- sion of O 2 Lamella Gill filaments

18. 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. Tracheoles Mitochondria Muscle fiber 2.5  m Tracheae Air sacs External opening Trachea Air sac Tracheole Body cell Air

19. Lungs 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 Pharynx Larynx (Esophagus) Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) Capillaries Left lung Dense capillary bed enveloping alveoli (SEM) 50  m Alveoli Branch of pulmonary artery (oxygen-poor blood) Branch of pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasal cavity

20. 42.6 Breathing Ventilates the Lungs 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. Anterior air sacs Posterior air sacs Lungs 1 mm Airflow Air tubes (parabronchi) in lung Anterior air sacs Lungs Second inhalation First inhalation Posterior air sacs 3 2 4 1 4 3 1 2 Second exhalation First exhalation

21. How a Mammal Breathes 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. Rib cage expands. Air inhaled. Air exhaled. Rib cage gets smaller. 12 Lung Diaphragm

22. Control of Breathing Involuntary action controlled by the medulla oblongata. Uses pH as an indicator of CO 2 concentrations of the surrounding tissues. CO 2 reaction with H 2 O of CS fluid creating carbonic acid. This dissociates into a bicarbonate ion and H +. 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

23. 42.7 Adaptations for Gas Exchange Include Pigments that Bind and Transport Gases O 2 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 O 2 When 1 subunit binds to O 2 the others change shape to become more susceptible to O 2. When pH drops, it releases more O 2 (Bohr shift). Iron Heme Hemoglobin (b) pH and hemoglobin dissociation P O (mm Hg) 2 020406080100 0 20 40 60 80 100 Hemoglobin retains less O 2 at lower pH (higher CO 2 concentration) pH 7.2 pH 7.4 O 2 saturation of hemoglobin (%)

24. Carbon Dioxide Transport CO 2 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 CO 2 again. Body tissue Capillary wall Interstitial fluid Plasma within capillary CO 2 transport from tissues CO 2 produced CO 2 H2OH2O H 2 CO 3 Hb Red blood cell Carbonic acid Hemoglobin (Hb) picks up CO 2 and H +. H+H+ HCO 3  Bicarbonate  HCO 3  To lungs CO 2 transport to lungs HCO 3  H 2 CO 3 H2OH2O CO 2 H+H+  Hb Hemoglobin releases CO 2 and H +. CO 2 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. Putting the Two Together 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 (a) The path of respiratory gases in the circulatory system CO 2 O2O2 8 1 2 3 7 64 5