Biology

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TOPIC 1 A LEVEL BIOLOGY
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CIRCULATORY SYSTEMS Describe why animals have a heart and circulatory system. Animals have a heart and circulatory system because diffusion isn't sufficient on it's own. The blood and nutrients need to have pressure to help push things around the body.
Define the terms 'mass flow' and 'diffusion' Mass Flow= movement of a fluid in one direction usually through a system of tube like vessels Diffusion= the passive movement of a substance from an area of high concentration to an area of low concentration until equilibrium.
Describe the features of a mass flow system and explain why certain organisms need to use mass flow. A mass flow system means that the substances move in a certain direction due to a force. Certain animals need a mass flow system because diffusion isn't sufficient on its own.
Describe the differences between 'open circulatory' and 'closed circulatory' systems. Open circulatory system= The heart pumps blood out and the substances diffuse between the blood and the cells. Closed circulatory system= The blood is enclosed within tubes. This creates a higher pressure, which means blood flows at higher speeds and is more efficient
Identify key features of single and double circulatory systems and explain these features. Single= Blood passes through the heart once for each complete circuit of the body, is carried at a lower pressure. Double= The blood passes through the heart twice. There's two different circuits so the blood can be pumped at different pressures.
Describe the structure of the pulmonary circulation and systemic circulation. Pulmonary = Carries de-oxygenated blood to the lungs to become oxygenated Systemic= Carries oxygenated blood to every cell in the body and returns de-oxygenated blood back to the heart.
List the key components of blood and describe their functions. Red blood cells (erythrocyte)= Transports oxygen as haemoglobin and removes waste products. Bi-concave shape,no nucleus White blood cells (Leukocytes) = Protects against infections Platelets= Helps blood clot. Plasma=liquid carrying nutrients etc
Describe with the aid of a diagram the structure of a water molecule illustrating hydrogen bonding. Hydrogen bond between oxygen and hydrogen molecule. Hydrogen=positive Oxygen = negative Attraction between positive and negative charges.
Describe how the polar nature of water makes it useful as a solvent. Many chemicals dissolve easily in water. This is because of the uneven charge. The negative molecule is attracted to the hydrogen in water and the positive molecules are attracted the oxygen in water.
Describe the function or arteries, veins and capillaries and how it relates to their function. Arteries= Narrow lumen, Thick walls, more collagen, no valves. Carries blood away from the heart at high pressure. Veins= Wide lumen, Thinner walls, Less collagen, has valves. Carries blood back to the heart. Capillaries= Allows substances to diffuse to cells. One cell thick.
Explain why the walls of the ventricles are thicker than the walls of the atria. The walls of the ventricles are thicker than the atria because the blood from the ventricles is either pumped to the lungs or around the whole body. The thicker walls help push the blood at a higher pressure to ensure the blood moves fast and efficiently.
Explain why the left ventricle wall is thicker than the right ventricle wall. The left ventricle wall is thicker because it has to pump the blood throughout the whole body and the thicker wall helps to get the blood to a higher pressure and the blood travels faster. The blood from the right ventricle is only going to the heart so is at a lower pressure.
Describe the main stages of the cardiac cycle. DIASTOLE= Heart relaxing, chambers open. Atria fill with blood. Cuspid valves= closed. Valves open as pressure higher than in ventricles. Blood into ventricles. 70% of blood flows from atria to ventricles. PASSIVE MOVEMENT.
Describe the main stages of the cardiac cycle. ATRIAL SYSTOLE= Atria contract and release last 30% of blood. Started by natural electrical impulse near the SAN (pacemaker)
Describe the main stages of the cardiac cycle. VENTRICULAR SYSTOLE= Ventricles contract when the impulse reaches apex of septum. Pushes blood upwards. Cuspid valves close to stop back flow to atria. Semi-lunar valves open as pressure is higher in ventricles than aorta.
Describe and explain what causes the valves to open and close. As the atria fill, pressure of blood against the cuspid valves and pushes them open. Pressure increases in ventricles. Pushes blood up and out. Pressure of blood against the cuspid valves and closes them.
Define what is meant by the terms myocardial infarction, stroke and angina. Myocardial infarction= Heart attack. Damage to/death of part of heart muscle due to lack of blood. Stroke= Death of brain cells as they are starved of oxygen/blood. Angina= Pains in chest/left shoulder. Not enough blood to heart. Respire anaerobically
Define what is meant by the terms aneurysm, Thrombosis and Endothelial dysfunction. Aneurysm= Swelling of the artery wall, causes the wall to become inelastic Thrombosis= Formation of blood clot in blood vessel. Endothelial dysfunction=
Define what an atheroma is and explain how it can turn into a plaque. Atheroma= Fatty deposit in the inner lining of an artery, resulting from atherosclerosis. Made of WBC and cholesterol. Atheroma into plaque= Calcium salts and fibrous tissue builds up at site. Hard swelling of a plaque.
Explain how a plaque leads to narrowing of an artery and thrombosis. Plaques are the build up of fibrous tissues which means that the artery wall loses some of its elasticity; it hardens.
List the sequence of events that can lead to atherosclerosis Endothelium damaged, inflammatory response, WBC move to artery wall, Cholesterol accumulates to atheroma. calcium salts + fibrous tissue to plaque. Artery hardens. Rising blood pressure. Positive feedback system.
Explain how atherosclerosis can lead to increasing blood pressure and how this is an example of a positive feedback system. Plaques cause the lumen to become narrower. Heart needs to pump harder to push the blood. This causes a higher blood pressure. Higher blood pressure leads to the endothelium being damaged, which can cause more plaques to form.
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