The Structure and Function of the heart

Cardiac Muscle The heart pumps blood around the body. It is able to do this due to: –A–A series of contractions and relaxations of the cardiac muscle. –O–One way valves to ensure blood flows the correct direction. –T–The right and left side of the heart is divided by a muscle called the septum. The left ventricle has a thicker muscle and smaller chamber then the Right Ventricle because ????? {your turn to prove you are awake}

The Valves The valves stop blood flowing from the ventricles back to the atrium. There are two main valves do this: –Tricuspid valve (Right side) –Bicuspid or mitral valve (left side) The semi-lunar valve will stop the blood flowing back into the heart after it enters the artery.

Cardiac Cycle Describes how the blood flows through heart. Blood enters the atria, but blocked by the valves Walls of atria contract, pressure forces blood through valves Blood enters the ventricle Ventricles contract, the increase pressure on the blood will close the valves to atrium As ventricle contracts, high blood pressure will force open the semi-lunar valves Blood forced out through the artery, which pushes other blood to the heart

Diastole and Systole When the chamber in the heart is contracting, it is called systole. When the chamber in the heart is relaxing, it is in diastole. Use a table to compare the two. In your table include changes in chamber size, pressure in chamber, blood flow and relaxing/contracting, pressure on artery valves.

Graphing the Heart Beat

Coronary circulation The heart is a muscle and so needs to supply itself with blood. The vessels that supply the heart with blood is called the coronary circulation. The coronary artery brings the blood to the heart muscle. The coronary vein takes the blood away from the heart to the right atrium. Atrium is singular, atria is plural.

Coronary Heart Disease Coronary heart disease is when the coronary artery becomes blocked with cholesterol and fatty tissue, thus some parts of the heart muscle tissue are starved of oxygen.

Causes of Coronary Heart Disease Factors that lead to Coronary Heart Disease: 1.Heredity 2.High blood pressure 3.Diet 4.Smoking 5.Stress 6.Lack of exercise.

Heart Rate Heart beats about 70 times a minute. The heart rate is the number of beats per minute and this will change if we exercise (why?) OR frightened. (part of the fight or flight condition) The heart rate will increase if the hormone adrenaline is released from the adrenal gland. Heart rate decreases when we are sleeping as the organs are working less.

Nerve pulses from the medulla controls the heart rate. Sensors in the aorta detect increases of CO2 in the blood plasma and sends message to medulla. Medulla sends message along the accelerator nerve The accelerator nerve will increase the heart rate. The decelerator nerve decreases the heart rate.

The increasing and decreasing the heart rate are known as reflex actions. Using your text book, draw a flowchart that shows how the medulla controls the heart rate. As part of your flowchart include the affect of the Carbon Dioxide (called the feedback mechanism)