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CET - Animal Transpo
OCR A level Biology F211 Transport in Animals
| Question | Answer |
|---|---|
| Why do multicellular organs need transport systems? | Too large for diffusion to be feasible. Active, so they need a constant, rapid supply of oxygen and glucose, so many cells can respire very quickly. |
| What is circulatory system in fish? | The heart pumps blood to the gills, to pick up oxygen, and then on through the rest of the body, to deliver the oxygen, in one single circuit. |
| What is circulatory system in mammals? | Heart divided down the middle - right side pumps to lungs to pick up oxygen; blood travels from the lungs to left side of the heart; pumps blood to rest of body; blood returns to the heart, entering right side again. |
| What are the different loops called? | The loop sending blood to the lungs is called the pulmonary system and the loop sending blood to the rest of the body is called the systemic system. |
| What are advantages of double circulatory systems? | The heart can give the blood an extra “push” between the lungs and the rest of the body. The blood travels faster, so oxygen is delivered to tissues more quickly. |
| What is a closed circulatory system? | The blood is enclosed inside blood vessels. Heart pumps blood into arteries, which branch out into millions of capillaries. Substances diffuse from capillaries to cells, but blood stays in vessels. Veins take the blood back to the heart. |
| What is an open circulatory system? | Blood is not always enclosed in vessels and chambers, but flows freely through the body cavity. |
| Which vessels does blood enter the heart through? Where into? | Blood enters the heart through the superior and inferior vena cava, into the right atrium. |
| Which valve does it go through from right atrium to right ventricle? Which valve does it travel through into pulmonary artery? | It travels into the right ventricle through the atrioventricular valve, and then leaves through the pulmonary artery via the semi-lunar valve. |
| After becoming oxygenated at the lungs, where does blood go? | Enters left atrium through the pulmonary vein, travels into the left ventricle through the atrioventricular valve, and then leaves the left side of the heart via the aorta. |
| Why are there valves in the heart? | Prevent blood flowing wrong way. |
| Atrioventricular valves? | Link the atria to the ventricles. |
| Semi-lunar valves? | Link the ventricles to the pulmonary artery and the aorta. |
| Valve facts? | Only open one way. Whether they are open or closed depends on the relative pressure of the heart chambers. If the pressure is higher behind a valve, it is forced open. If the pressure is higher in front of a valve, it is forced shut. |
| Why are walls of different parts of the heart a different thickness? | Each of the four chambers of the heart has a different function. The more work that a chamber has to do, the more muscle it needs, so the thicker its wall is. |
| Which parts of the heart have the thinnest walls? | The atria have the thinnest walls, because they only need to push blood from the atria into the ventricles, whereas ventricles have to push blood all the way to the lungs / body. |
| Which ventricle has thicker, more muscular walls? | The left ventricle has thicker, more muscular walls than the right ventricle, because it needs to contract powerfully because it needs to contract powerfully to pump blood all the way round the body. |
| What is the cardiac cycle? | Ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating round the body. |
| Why do valves open and close? | The volume of the atria and ventricles changes as they contract and relax, altering the pressure in each chamber, causing valves to open and close, directing blood flow through the heart. |
| What happens when ventricles relax and atria contract? | Atria fill with blood, increasing pressure. Higher pressure in atria than ventricles opens AV valves, blood flows to ventricles. Atria contract, increasing pressure, forcing blood out. |
| What happens when ventricles contract and atria relax? | Pressure is higher in the ventricles than the atria - AV valves close to prevent backflow. The high pressure in the ventricles opens the semi-lunar valves – blood is forced out into the pulmonary artery and aorta. |
| What happens when the ventricles and atria both relax? | Higher pressure in pulmonary artery and aorta than heart chambers causes SL valves to close, preventing backflow. Atria fill with blood due to the higher pressure in the vena cava and pulmonary vein. |
| MYOGENIC. | Cardiac muscle can contract and relax without receiving signals from nerves, and this pattern of contraction controls the regular heartbeat. |
| Where does heart action begin to be controlled? | SAN in wall of right atrium. |
| What does SAN do? | Send out regular waves of electrical activities to atrial wall, causing right and left atria to simultaneously contract. |
| What prevents waves of electrical activity being passed directly from the atria to the ventricles? | Band of non-conducting collagen. |
| Where are signals transferred? How long is the pause? | AVN. 0.1 seconds. |
| Where is the electrical activity passed to from the AVN? | The bundle of His, a group of muscle fibres which conduct waves to the finer muscle fibres in right and left ventricle walls, called the Purkyne tissue. |
| Where does Purkyne tissue carry the waves? | Into the muscular walls of the right and left ventricle, causing them to simultaneously contract from the bottom up. |
| Describe arteries. | Carry blood from heart to the rest of the body. Thick, muscular walls. Elastic tissue to cope with high pressure from heartbeat Folded endothelium, allowing to expand – to cope with high pressure. |
| Describe capillaries. | Smallest of the blood vessels. Substances like glucose and oxygen are exchanged between cells and capillaries, so they are adapted for efficient diffusion, e.g. their walls are only one cell thick. Capillaries connect to veins. |
| Describe veins. | Take blood back to the heart under low pressure. Wider than arteries, little elastic or muscle tissue. Contain valves, stops backflow. Blood flow helped by contraction of body muscles. |
| How does blood form tissue fluid (name. | Pressure filtration. |
| How does blood form tissue fluid (process). | At arterial end of capillary bed, pressure in capillaries is greater than in tissue fluid. Difference in pressure forces fluid of capillaries and into spaces around cells, forming tissue fluid. |
| What happens at the venous end of the capillaries? | Reduced pressure in capillary bed lowers water potential, so it is lower than tissue fluid. Some water re-enters the capillaries from tissue fluid, by osmosis. |
| How does excess tissue fluid return to the blood? | Via the lymph system. |
| What are the smallest lymph vessels called? | Lymph capillaries. |
| Why are there valves in lymph vessels? | Prevent backflow. |
| Where does lymph move towards? | Main lymph vessels (thorax), returning to blood near heart. |
| Where are red blood cells found? | Blood. |
| Where are white blood cells found? | Blood and lymph. Only enter tissue fluid when there is an infection. |
| Where are platelets found? | Blood. Only in tissue fluid if capillaries are damaged. |
| Where are proteins found? | Blood. Most too large to get through capillary walls. Antibodies in lymph. |
| Where is water found? | Blood, tissue fluid and lymph. Higher water potential in lymph and tissue fluid. |
| Where are solutes found? | Everywhere, can move freely. |
| Describe Hb. | Large protein, quaternary structure, four polypeptide chains, each with a haem group containing iron. High affinity for oxygen, each molecule can carry four oxygen molecules. |
| What happens to oxygen in the lungs? | Joins to iron in haemoglobin to form oxyhaemoglobin. Reversible reaction – oxygen can dissociate, and turns back to Hb. |
| Equation for Hb + O2? | Hb + 4O2 (reversible) HbO8 |
| What is partial pressure? | Measure of the concentration of a gas. |
| How does the pO2 affect oxygen unloading? | O2 loads onto Hb where there is a high pO2, and unloads where there is a low pO2. |
| What happens in alveoli? | High pO2 so oxygen loads onto haemoglobin to form oxyhaemoglobin. |
| What happens in respiring tissues? | Use up oxygen, lower pO2, red blood cells unload oxygen. |
| What does the dissociation curve show? | Saturation of Hb for a given pO2. |
| Why is the graph S shaped? | When Hb combines with first O2 molecule, shape alters so it is easier for other molecules to join. But as it becomes more saturated, it gets harder for other molecules to join. |
| Why does fetal haemoglobin need higher O2 affinity than adult? | Oxygen unloads from mother’s blood, across the placenta. By the time mother’s blood reaches placenta, O2 saturation has decreased so fetal Hb needs higher O2 affinity to get enough O2 to survive. |
| How does CO2 concentration affect oxygen unloading? | High pCo2 causes Hb to give up O2 more readily, so more oxygen can get to cells during activity. |
| Why does increased pCO2 increase oxygen unloading? | Linked to how CO2 affects blood pH. |
| Where does most of the CO2 from respiring tissues go? | Diffuses into red blood cells, converted to carbonic acid by carbonic anydrase. |
| What happens to carbonic acid? | Splits into hydrogen ions and hydrogencarbonate ions. |
| What does increase in hydrogen ions cause? | Oxyhaemoglobin unloads oxygen so that Hb can take up hydrogen ions, forming haemoglobinic acid. |
| What happens to hydrogencarbonate ions? | Diffuse out of red blood cells and transported in blood plasma. |
| What happens to CO2 when blood reaches the lungs? | Low pCO2 causes hydrogencarbonate and hydrogen ions to recombine into CO2. CO2 diffuses into alveoli and is breathed out. |
Created by:
emm142
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