Lecture 11 Outline (Ch. 42) I. Circulatory Systems II. Human Heart III. Blood & Vessels Cardiovascular disorders V. Methods – bulk flow vs. diffusion VII. Gas exchange and partial pressures Breathing mechanisms Preparation for next lecture

Circulation carries energy, dissolved gasses, wastes 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

Circulatory systems are open or closed 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 Interstitial fluid Small branch vessels In each organ Blood Dorsal vessel (main heart) Auxiliary hearts Ventral vessels (b) A closed circulatory system (a) An open circulatory system Tubular heart Pores

Vertebrates have a closed circulatory system 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

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

Amphibians, reptiles, mammals The Vertebrate Heart Systemic circuit Systemic capillaries Right Left A V Lung Pulmonary circuit Key Oxygen-rich blood Oxygen-poor blood 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! Double circulation – pulmonary circuit and systemic circuit Amphibians, reptiles, mammals

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

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

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

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

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

The Cardiac Cycle & Blood Pressure 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

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

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)

Blood Plasma Blood Primarily water Dissolved proteins and electrolytes Plasma fluid Cells Red blood cells – transport White blood cells – defense Platelets – clotting

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

Erythrocytes are short-lived 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

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

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

Blood is carried in vessels 21

Artery Vein SEM 100 µm Endothelium Smooth muscle Connective tissue Capillary Basal lamina Valve Arteriole Venule Red blood cell 15 µm LM

Blood Vessels Arteries Arteries Arterioles Capillaries Heart Carry blood away from heart Thick-walled: Smooth muscle/elastic fibers Withstand high pressure Venules Veins

Blood Vessels Arteries Arterioles Arterioles Capillaries Heart Control distribution of blood flow Smooth muscle expands / contracts Under hormone / NS control Venules Veins

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

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

Blood Vessels Arteries Arterioles Capillaries Heart Venules & Veins Carry blood towards the heart Thin-walled; large diameter One-way to prevent backflow Venules Veins

Blood Vessels Skeletal Muscle Pump: Vein Valve:

Blood Vessels Varicose veins occur if the vein valves become inefficient

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 (a) Normal artery (b) Partly clogged artery 50 µm 250 µm

Thought Question: If you are an athlete who trains at high elevations, what happens if you compete at a lower elevation? At high altitudes, the lower air pressure makes it more difficult for oxygen to enter our vascular systems.  Hypoxia usually begins with the inability to do normal physical activities, such as climbing a short flight of stairs without fatigue.  Other early symptoms of "high altitude sickness" include a lack of appetite, distorted vision, and difficulty with memorizing and thinking clearly. More red blood cells and capillaries are produced to carry more oxygen.  The lungs increase in size to facilitate the osmosis of oxygen and carbon dioxide.  There is also an increase in the vascular network of muscles which enhances the transfer of gases. On returning to sea level after successful acclimatization to high altitude, the body usually has more red blood cells and greater lung expansion capability than needed.  Since this provides athletes in endurance sports with a competitive advantage, the U.S. maintains an Olympic training center in the mountains of Colorado.  Several other nations also train their athletes at high altitude for this reason.  However, the physiological changes that result in increased fitness are short term at low altitude.  In a matter of weeks, the body returns to a normal fitness level. 

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

Respiratory systems enable gas exchange 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

Gas Exchange Systems Gills Aquatic gas exchange Elaborately folded ( surface area) Contain capillary beds Gill size inversely related to [O2] Large gills = low [O2]

Gas Exchange Systems Fish Efficiency Dissolved O2 is < 1% of water (21% of air) Countercurrent exchange increases efficiency

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

Mammals Human Respiration Air enters through nose and mouth to pharynx Larynx (Esophagus) Trachea Right lung Bronchus Bronchiole Diaphragm (Heart) Left lung Nasal cavity Air enters through nose and mouth to pharynx Travels through larynx (voice box) Epiglottis directs travel Larynx contains vocal cords, which allow vocalization- exhaled air vibrates the cords, and produces sound. Stretching the cords can change pitch 37

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

Human Respiration Gas exchange is driven by differences in pressures Exhaled air Inhaled air Pulmonary arteries Systemic veins Alveolar capillaries spaces epithelial cells Heart CO2 O2 Body tissue 8 1 2 3 7 6 4 5 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

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

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

Breathing Mechanisms Inhalation: Rib muscles contract to expand rib cage Diaphragm contracts (down) expands the volume of thorax and lungs Rib cage expands. Air inhaled. exhaled. Rib cage gets smaller. 1 2 Lung Diaphragm Some air always remains in the lungs to fill alveoli and breathing tubes and prevent collapse Thoracic cavity expands, produces negative pressure which draws air into the lungs 42

Breathing is involuntary Breathing Mechanisms Homeostasis: Blood pH of about 7.4 CO2 level decreases. 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 Breathing is involuntary Controlled by respiratory center of the brain Adjusts breath rate & volume based on sensory input Maintain a constant concentration of CO2

Things To Do After Lecture 11… Reading and Preparation: Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. Ch. 42 Self-Quiz: #2, 3, 4, 6, 7 (correct answers in back of book) Read chapter 42, focus on material covered in lecture (terms, concepts, and figures!) Skim next lecture. “HOMEWORK” (NOT COLLECTED – but things to think about for studying): Compare and contrast veins and arteries in terms of structure and function. Diagram the path blood takes from the body, to the heart and lungs, back to the body. 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? Explain homeostatic control of breathing.