The Heart

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  • The Circulatory system
    • The heart
      • Adaptations:
        • The semi-lunar valves link ventricles to the pulmonary artery and aorta.
        • The ventricles have thicker walls than the atria because they have a further distance to push
        • The atrioventricular valves link atria and ventricles together and prevent backflow. The left is the bicuspid and the right is the tri-cuspid.
        • Left ventricle has a thicker, more muscular wall because it has to pump blood all the way around the body.
        • The cords on the atrioventricular valves attach to the ventricles to stop blood being forced into the atria.
      • Blood Vessels
        • The pulmonary artery is connected to the right ventricle and carries de-oxygenated blood to the lungs.
        • The Vena Cava is connected to the right atrium and brings de-oxygenated blood to the body.
        • The pulmonary vein is connected to the right atrium and brings oxygenated blood back from the lungs.
        • The aorta is connected to the left ventricle and carries blood to all parts of the body
      • Coronary arteries supply the heart with oxygen. Blockages of these leads to a myocardial infarction.
    • The Cardiac Cycle
      • Diastole Blood enters the heart through the pulmonary vein and the vena cava. The atria fills and so does the pressure. The atria and ventricles are relaxed and have a low pressure and the semi-lunar valves close.
        • Atrial Systole The remaining blood around 20% is forced into the ventricles. The ventricles are relaxed.
          • Ventricular Systole After a delay for the ventricles to fill the blood, the blood pressure increases and the atrioventricular valves are shut and this forces the semi-lunar valve open. The blood is then pumped out of the heart.
            • Diastole Blood enters the heart through the pulmonary vein and the vena cava. The atria fills and so does the pressure. The atria and ventricles are relaxed and have a low pressure and the semi-lunar valves close.
              • Atrial Systole The remaining blood around 20% is forced into the ventricles. The ventricles are relaxed.
                • Ventricular Systole After a delay for the ventricles to fill the blood, the blood pressure increases and the atrioventricular valves are shut and this forces the semi-lunar valve open. The blood is then pumped out of the heart.
        • Cardiac output is the amount of blood pumped in one minute.
          • Cardiac output=heart rate x stroke volume
        • Control of the cardiac cycle
          • Myogenic-the contracted is forced from inside the muscle
          • The SAN releases an electrical impulse forcing the atria to contract. A layer of insulator cells prevents the impulse reaching the ventricles.
            • The impulse reaches the AVN, and after a delay, sends a message to the bundle of his.
              • This message is sent to the Purkyne fibres. The ventricles then contract from the bottom, forcing all blood from the heart.
      • Cardiovascular diseases
        • Atheroma is where deposits of fatty material collect under the epithelium.
          • The white blood cells repair them too much and increase the size of it.
            • It then breaks the lining of the epithelium and reduces the lumen-forming an atheroma
        • Aneurysm is a swelling on the artery due to high pressure caused by an atheroma. It can burst leading to a haemorrhage.
        • Thrombosis is a blood clot created from an atheroma. The platelets cause this blood to clot and form a blockage.
        • Myocardial Infarction
          • This is where a coronary artery is blocked and stops the blood from supplying the heart with oxygen. Often fatal.
        • Risk factors of CHD
          • High blood pressure increases the chance of an atheroma and therefore a heart attack.
          • High cholesterol increases the fatty deposits in arteries and increases the chance of a heart attack.
          • Cigarette smoking produces carbon monoxide which binds with haemoglobin reducing the amount of oxygen going around the body.
    • Cardiac output=heart rate x stroke volume

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