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Lecture 18 Transport in Animals II Blood Type • • • All cells of the human body have surface proteins and other molecules that serve as "self" markers. The human body also has antibodies that recognize markers on foreign cells. In a blood transfusion, or even a pregnancy, it is important that there is no possibility of an interaction between antibodies and foreign markers. ABO Blood Typing • • • • ABO blood typing is based on surface markers on red blood cells. Surface markers are glycoproteins known as agglutinogens have corresponding antibodies. Type A has A markers; type B has B markers; type AB has both markers; type O has neither marker. If bloods of incompatible donors and recipients are mixed, agglutination (clumping) will occur. Blood Donations • A person with type A blood can donate blood to a person with type A or type AB. • A person with type B blood can donate blood to a person with type B or type AB. • A person with type AB blood can donate blood to a person with type AB only. • A person with type O blood can donate to anyone. • A person with type A blood can receive blood from a person with type A or type O. • A person with type B blood can receive blood from a person with type B or type O. • A person with type AB blood can receive blood from anyone. • A person with type O blood can receive blood from a person with type O only. Blood Groups Blood Group O A B AB Antigen - A B A+B Antibody a+b b a - Rh Blood Typing • • • • • An Rh -- person (lacks this marker) transfused with Rh+ blood (has this marker) will produce antibodies to the Rh marker. Occasionally, a baby will inherit an Rh positive blood type from its father while the mother has an Rh negative blood type. The baby's life could be in great danger if the mother's Rh negative blood attacks the baby's Rh positive blood. If this happens, an exchange transfusion may save the baby's life. There are risks in pregnancy to a second Rh+ child if an Rh -woman bore a previous child who was also Rh+ and thus left behind some antibodies that can now seep into this second child and cause clumping. In erythroblastosis fetalis, too many cells may be destroyed and the fetus dies. Medical treatment (RhoGam) given to the mother after the birth of the first Rh+ baby can inactivate the Rh antibodies. Blood and Oxygen • Hemoglobin is a protein molecule with 4 protein subunits (2 alphas and 2 betas) • Each of the 4 sub-units contains a heme group which gives the protein a red color • Each heme has an iron atom in the center which can bind an oxygen molecule (O2) • The 4 hemes in a hemoglobin can carry a maximum of 4 oxygen molecules • When hemoglobin is saturated with oxygen it has a bright red color; as it loses oxygen it becomes bluish (cyanosis) Hemoglobin -1 • The iron in each haem group binds an oxygen molecule. • Release of oxygen from hemoglobin is called dissociation. • The amount of oxygen that can bind hemoglobin is determined by the concentration or partial pressure. • The greater the partial pressure of oxygen the more hemoglobin becomes saturated. Hemoglobin - 2 • At the alveolar pO2 of 105 mm Hg at sea level the hemoglobin will be about 97% saturated, but the saturation will fall at high altitudes. • At 12,000 feet altitude alveolar pO2 will be about 60 mm Hg and the hemoglobin will be 90% saturated. • At 29,000 feet (Mt. Everest) alveolar pO2 is about 24 mm Hg and the hemoglobin will be only 42% saturated. • At very high altitudes most climbers must breath pure oxygen from tanks. • The developing fetus cannot breathe and must get all of its blood from the placenta. • Fetal blood has a very low pO2, about 30 mm Hg, equivalent to living at 26,000 feet altitude. • To extract more oxygen from the mother's blood fetuses make a special hemoglobin (hemoglobin F) which has a very high affinity for oxygen. The Bohr Effect • Hemoglobin must bind oxygen tightly to load up efficiently in the lungs, but this makes it hard to release the oxygen in the tissues • Some unloading occurs because the tissue pO2 is low, causing oxygen to diffuses from the blood • Active tissues make lots of acid (carbonic and lactic) and this also helps to unload oxygen from the hemoglobin • At low pH hemoglobin has a lower affinity for oxygen; this will cause more oxygen to come off in the tissuesimportant in exercise • The increased unloading of O2 at low pH is known as the Bohr Effect. • Hemoglobin also has a lower affinity for oxygen at higher temperatures. The Bohr Effect Blood Flow Hypoxia • Hypoxia is tissue oxygen deficiency. • Brain is the most sensitive tissue to hypoxia: complete lack of oxygen can cause unconsciousness in 15 sec and irreversible damage within 2 min. Types of Hypoxia Type of Hypoxia O2 Uptake in Lungs Hemoglobin Circulation Tissue O2 Utilization Hypoxic Low Normal Normal Normal Anemic Normal Low Normal Normal Ischemic Normal Normal Low Normal Histotoxic Normal Normal Normal Low Causes of Hypoxia • Hypoxic: high altitude, pulmonary edema, hypoventilation, emphysema, collapsed lung • Anemic: iron deficiency, hemoglobin mutations, carbon monoxide poisoning • Ischemic: shock, heart failure, embolism • Histotoxic: cyanide poisoning (inhibits mitochondria Carbon monoxide (CO) poisoning: • CO binds to the same heme Fe atoms that O2 binds to • CO displaces oxygen from hemoglobin because it has a 200X greater affinity for hemoglobin. • Treatment for CO poisoning: move victim to fresh air. Breathing pure O2 can give faster removal of CO Cyanide poisoning: • Cyanide inhibits the cytochrome oxidase enzyme of mitochondria • Two step treatment for cyanide poisoning: 1) Give nitrites Nitrites convert some hemoglobin to methemoglobin. Methemoglobin pulls cyanide away from mitochondria. 2) Give thiosulfate. Thiosulfate converts the cyanide to less poisonous thiocyanate Human Cardiovascular System The Cardiovascular System • The circulatory system functions in the delivery of oxygen, nutrient molecules, and hormones and the removal of carbon dioxide, ammonia and other metabolic wastes. • Capillaries are the points of exchange between the blood and surrounding tissues. • Veins carry blood from capillaries to the heart. • Venules are smaller veins that gather blood from capillary beds into veins. Pressure in veins is low, so veins depend on nearby muscular contractions to move blood along. The veins have valves that prevent back-flow of blood. Blood Vessels • Arteries - designed for high pressure are elastic: must swell to take up blood expelled by the heart. Swelling stretches elastic tissue and keeps the blood pressure fairly high between heart beats. • Small arteries (arterioles) have muscles that contol their diameters (precapillary sphincters): used to control blood flow through an organ. • Veins – designed for low pressure, expand to take up blood when animal is not active. • Capillaries - This is where materials are delivered from blood to cells, and vice versa, thin: one layer of flattened (squamous) cells, not elastic . ARTERY VEIN Structure of the Human Heart • • • • • The heart has four chambers through which blood is pumped. The upper two are the right and left atria. The lower two are the right and left ventricles. Left side deoxygenated blood. Right side oxygenated blood. Heart Valves • Four types of valves 1. 2. 3. 4. • • The tricuspid valve is located between the right atrium and right ventricle. The pulmonary or pulmonic valve is between the right ventricle and the pulmonary artery. The mitral valve is between the left atrium and left ventricle. The aortic valve is between the left ventricle and the aorta. Under normal conditions, the valves let blood flow in just one direction. Blood flow occurs only when there's a difference in pressure across the valves that causes them to open. The Cardiac Cycle • The sequence of events during a complete heart beat. • Systole – contraction and Diastole - relaxation. • Stage 1 – Atrial diastole, both atria and ventricles are relaxed. Blood enterr the atria under low pressure. As the atria fill with blood pressure rises and eventually forces the tricuspid and bicuspid valves to open. • Stage 2 – Atrial systole, two atria contract at the same time and blood pumped into the ventricles. • Stage 3 – Ventricular systole, 0.2 secs later the ventricles contract this causes the cuspid valves close, closing makes a sound, “lub”. The semi lunar valves of aorta and pulmonary artery open and blood enters. • Stage 4 – Ventricular diastole, high pressure in aorta and pulmonary closes the semi-lunar valves, closing makes a second sound, “dub.” Heartbeat • One complete heartbeat consists of one systole and one diastole. • Human heartbeats originate from the sinoatrial node (SA node) near the right atrium. • A discharge from this natural "pacemaker" causes the heart to beat. This pacemaker generates electrical impulses at a given rate, but emotional reactions and hormonal factors can affect its rate of discharge. This lets the heart rate respond to varying demands. • Modified muscle cells contract, sending a signal to other muscle cells in the heart to contract. • The signal spreads to the atrioventricular node (AV node). • Signals carried from the AV node, through bundle of His fibers and Purkinjie fibers cause the ventricles to contract simultaneously. Heat Beat Regulation of Heart Rate • Blood flow can be increased by increasing the blood pressure (higher cardiac output, constriction of many arterioles) • It can also be increased by opening up (dilating) arterioles in the tissue which needs more blood • Both cardiac output and blood vessel diameter are controlled by hormones and nerves Heart Disease • 40% of all premature deaths caused by cardiovascular disease. • Athersclerosis – development of a clot in arteries. • Once artery is blocked the tissue it supplies will suffer oxygen starvation will become damaged or die. Assignment 5 Read Chapter 14 Q1.How is heart rate controlled during exercise? Q2. If exercise is a good way to keep your heart healthy, why is there a chance of having a heart attack during vigorous exercise? Q3.How do electrocardiograms(ECGs) use the cycle to detect abnormalities in the heart?