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KS4 Biology

KS4 Biology. The Heart and Circulatory System. Heartbeat animation. Stages of a heartbeat . Stage 1: A heartbeat begins with the heart muscle relaxed and valves closed . Blood flows into the two atria and both sides fill up with blood.

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KS4 Biology

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  1. KS4 Biology The Heart and Circulatory System

  2. Heartbeat animation

  3. Stages of a heartbeat Stage 1: A heartbeat begins with the heart muscle relaxed and valves closed. Blood flows into the two atria and both sides fill up with blood. This blood has to be pushed through the valves to get into the ventricles. How does this happen?

  4. Stages of a heartbeat Stage 2: The atria contract and the blood is squeezed which causes the valves leading to the ventricles to open. Blood then flows from the atria into the ventricles. What happens to the open valves when the atria are empty?

  5. Stages of a heartbeat Stage 2 (continued): The valves between the atria and the ventricles close. This prevents any backflow. What happens next to the blood in the ventricles?

  6. Stages of a heartbeat Stage 3: Almost immediately, the ventricles contractand the blood is squeezed again. The pressure of the blood forces open the valves leading out of the heart. Blood is pumped out of the heart. What happens to the open valves when the ventricles are empty?

  7. Stages of a heartbeat Stage 3 (continued): When the ventricles are empty, the valves leading out of the heart close and the heart muscle relaxes. This completes the sequence of contraction and relaxation in one heartbeat. What will happen next?

  8. Stages of a heartbeat Stage 1 (again): The atria fill up with blood as the heartbeat sequence begins again. Why are the walls of the atria thinner than the walls of the ventricles? Why is the wall of the left ventricle thicker than the right ventricle?

  9. ---Blood vessels on the outside of the heart- coronary arteries---Muscles of the heart are thick-so nutrients and oxygen in the blood inside is not able to diffuse to all the muscle quickly----so heart muscle needs constant supply of nutrients and oxygen –to keep on working- coronary arteries does it --- If a coronary artery gets blocked the cardiac muscle run short of oxygen --- can not respire, so it does not have the energy to contract-heart stops beating --- HEART ATTACK or CARDIAC ARREST

  10. Pacemaker --The rate at which the heart beats is controlled by a patch of muscle in the right atrium called PACEMAKER -- It sends electrical signals through the walls of the heart at regular intervals, according to the need of the body -- If it stops working-an artificial pacemaker is placed to do the job Systole Cardiac muscle contracts-heart becomes smaller-squeezing blood out Diastole Cardiac muscle relaxes –heart becomes larger-allowing the blood to flow into atria and ventricles

  11. Blood flow through valves --there is a valve each between left and right atrium and ventricle-atrioventricular valves -- valve on the left side of the heart –made up of 2 parts-bicuspid /mitral valve -- valve on the right side of the heart –made up of 3 parts-tricuspid valve Function -- to stop blood flowing back from ventricles to atria. It is important as when ventricles contract, the blood is pushed up into the arteries, not back into atria --tendons attached to the valves stop them from going to far

  12. Questions: What kind of muscle is found in the heart? Which part of the heart receive blood from the a) the lungs b) the body? Which part of the heart pump blood into a) pulmonary artery b) aorta Why do ventricles have thicker walls than atria? Why does the left ventricle have a thicker wall than the right ventricle? What is the function of the coronary arteries? What is a) systole b) diastole Where are the atrioventricular valves? What is their function? Why are these valves supported by tendons? What is pacemaker?

  13. Listening to a beating heart: lub-dub What does a doctor hear when they listen to a patients’ heart? lub-dub, lub-dub, lub-dub, lub-dub, lub-dub, lub-dub… The sound of a heartbeat is the sound of the heart valves. The “lub” is caused by the closing of the valves leading to the ventricles. The “dub” is caused by the closing of the valves leading out of the heart.

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