Lecture #18 Date _____ Chapter 42 ~ Circulation and Gas Exchange

Overview

Questioning What do you think is important for gas exchange to occur? What will allow for greater gas exchange?

Gas exchange Uptake of O 2 and discharge of CO2 All gas exchange occurs through diffusion Rates depend on surface area and strength of concentration gradients (surface area:volume ratio needs to be large) Respiratory surfaces – thin and have large surface area, moist, O2 and CO2 are dissolved in water Depends on lifestyle/metabolic demands (aquatic, terrestrial, ecto/endotherm) Aquatic: gills (ventilation& countercurrent exchange) Terrestrial: tracheal systems & lungs

Question How do you think simple organisms respire? What is their body organization like? More complex organisms?

Diversity of gas exchange Bacteria/Protists – gas exchange across entire organism Sponges, cnidarians, flatworms – direct diffusion Earthworm/amphibians – breath through skin Birds – lungs with air sacs (1-way flow of air) More complex organisms – highly branched and folded respiratory organ (increase surface area)

Ventilation – current of water across gills so fresh O2 is near the gills Countercurrent Exchange

Countercurrent exchange – allows diffusion to occur along the entire length of capillary 80% efficient On land, gills would dry out and collapse (need moist surface for diffusion)

Question What are the advantages of living on land vs. living in water when it comes to respiration?

Advantages of air over water Higher percentage of O2 (210ml vs 6 ml per liter) No ventilation required (gas diffuses faster) However, respiratory surface has to be internal to keep diffusion surfaces moist

TRACHEAL TUBES -Air tubes bring O2 directly to cells (no circulatory system involvement) -Diffusion can move the air through or -Flight muscles can flex tubes (ventilation) to transport O2 more efficiently

Lungs - Mammalian respiratory systems – circulation involved Nasal cavity Pharynx Larynx (upper part of respiratory tract) – vocal cords Trachea (windpipe) Bronchi (tube to lungs) Bronchioles Alveoli (air sacs) Diaphragm (breathing muscle)

Warm-up Questions What allows for more efficient diffusion? What strategies do different organisms use to respire? List the organs of the respiratory system in order.

Respiratory Video

Question Describe the process of breathing in humans.

Breathing Positive pressure breathing: pushes air into lungs (frogs) Negative pressure breathing: pulls air into lungs (mammals) Inhalation: diaphragm contraction; Exhalation: diaphragm relaxation Tidal volume: amount of air inhaled and exhaled with each breath (500ml) Vital capacity: maximum tidal volume during forced breathing (4L) Residual air – increases with age or disease – efficiency goes down

Regulating breathing Regulation: monitors CO 2 levels in blood (medulla oblongata) CO2 + water = carbonic acid = lowers pH Slight drop in pH triggers a breathing response O2 levels have little effect on breathing unless O2 is severely depleted

Breathing Facts We breathe 22,000 times a day Hiccups – involuntary contractions of the diaphragm Sneeze – irritant in respiratory tract your body is trying to get rid of Yawn – not getting enough O2 to body (tiredness) Fetuses have been seen yawning Reading about yawning will make you yawn

Yawn Video

Next Step We have the oxygen in our lungs How do we get it to our cells? Two issues –Every cell needs gas exchange –Only 4.5 ml of oxygen will dissolve into blood at 1 time (very inefficient) – need help

Respiratory pigments: gas transport Needed for efficient transport of oxygen Oxygen transport- Hemocyanin: found in hemolymph of arthropods and mollusks (Cu) – blue blood Hemoglobin: vertebrates (Fe) Carbon dioxide transport- Blood plasma (7%) Hemoglobin (23%) Bicarbonate ions (70%) Deep-diving air-breathers- Myoglobin: oxygen storing protein

Protein review Cooperativity – the binding of one oxygen to hemoglobin, causes the other 3 active sites to have a HIGHER AFFINITY for oxygen Similar to allosteric activation What do you think the optimal pH is for hemoglobin?

How does hemoglobin load/unload? Individual whiteboard –Partial pressure = percentage gas X 760 mmHg –Write the partial pressures of O2 and CO2 in these locations Inhaled air Blood leaving the alveoli Blood entering capillaries near body cells Blood leaving capillaries of the body cells Blood nearing the alveoli Exhaled air

Warm-up Describe how hemoglobin binds and releases oxygen. What is the purpose of the circulatory system?

Bohr shift Hemoglobin releases oxygen (has less affinity for oxygen) at lower partial pressure for oxygen and at lower pH’s (more CO2)

Circulation system evolution, I Gastrovascular cavity (cnidarians, flatworms) Open circulatory hemolymph (blood & interstitial fluid) sinuses (spaces surrounding organs) Closed circulatory: blood confined to vessels Cardiovascular system heart (atria/ventricles) blood vessels (arteries, arterioles, capillary beds, venules, veins) blood (circulatory fluid)

Gastrovascular Cavity

Circulation system evolution, II Fish: 2-chambered heart; single circuit of blood flow Amphibians: 3-chambered heart; 2 circuits of blood flow- pulmocutaneous (lungs and skin); systemic (some mixing) Mammals: 4-chambered heart; double circulation; complete separation between oxygen-rich and oxygen poor blood

Double circulation From right ventricle to lungs via pulmonary arteries through semilunar valve (pulmonary circulation) Capillary beds in lungs to left atrium via pulmonary veins Left atrium to left ventricle (through atrioventricular valve) to aorta Aorta to coronary arteries; then systemic circulation Back to heart via two venae cavae (superior and inferior); right atrium

The mammalian heart Cardiac cycle: sequence of filling and pumping Systole- contraction Diastole- relaxation Cardiac output: volume of blood per minute Heart rate- number of beats per minute Stroke volume- amount of blood pumped with each contraction Pulse: rhythmic stretching of arteries by heart contraction

Tricuspid Valve Pulmonary Valve Mitral Valve Aortic Valve

The heartbeat Sinoatrial (SA) node (“pacemaker”): sets rate and timing of cardiac contraction by generating electrical signals Atrioventricular (AV) node: relay point (0.1 second delay to ensure atria empty) spreading impulse to walls of ventricles Electrocardiogram (ECG or EKG)

Why do the blood vessels have different structure? Capillaries endothelium (lining of smooth cells = less resistance to blood flow); basement membrane – cell attachment & selective permeability Arteries thick connective tissue; thick smooth muscle; endothelium; basement membrane Veins thin connective tissue; thin smooth muscle; endothelium; basement membrane

Blood flow in veins

Why is important to maintain blood pressure?

Water Potential Review

Diffusion O2 and CO2 passively diffuse Other solutes can travel between cells through bulk flow (caused by pressure) Arterial end of a capillary – net diffusion is out of capillary Venous end – net diffusion is in 85% of fluid that leaves the blood vessel will return at the venous end (other 15 % will be recycled by the lymphatic system)

The lymphatic system Lymphatic system: system of vessels and lymph nodes, separate from the circulatory system, that returns fluid and protein to blood Lymph: colorless fluid, derived from interstitial fluid Lymph nodes: filter lymph and help attack viruses and bacteria Body defense / immunity

Blood Plasma: liquid matrix of blood in which cells are suspended (90% water) Erythrocytes (RBCs): transport O 2 via hemoglobin Leukocytes (WBCs): defense and immunity Platelets: clotting Stem cells: pluripotent cells in the red marrow of bones Blood clotting: fibrinogen (inactive)/ fibrin (active); hemophilia; thrombus (clot)

Cardiovascular disease Cardiovascular disease (>50% of all deaths) Heart attack- death of cardiac tissue due to coronary blockage Stroke- death of nervous tissue in brain due to arterial blockage Atherosclerosis: arterial plaques deposits Arteriosclerosis: plaque hardening by calcium deposits Hypertension: high blood pressure Hypercholesterolemia: LDL, HDL

LDL vs HDL To Decrease LDL, try: minimize the intake of Saturated Fats minimize the intake of Trans Fats include foods with Soluble Fiber include Soy ProteinsSoy Proteins include Omega 3 -rich food such as Salmon, Fish Oils and FlaxseedSalmonFish Oils Flaxseed include GarlicGarlic keep a healthy weight keep an active lifestyle To Increase HDL, try: stay active reduce total fat intake to <30% quit smoking include Omega 3 -rich food such as Salmon and Fish OilsSalmonFish Oils moderate amount of Red Wine may helpRed Wine

Practice Discuss the processes of exchange of O2 and CO2 that occur at the alveoli and muscle cells of mammals. Include in your answer a description of the transport of these gases in the blood.