How the heart works Your heart is roughly the size of a fist and sits in the middle of your casket, slightly to the left  side. It’s the muscle at the centre of your  rotation system. It pumps blood around your body as your heart beats. This blood sends oxygen and nutrients to all corridor of your body, and carries down unwanted carbon dioxide and waste products. Structure of your heart Your heart is made up of 3 layers of kerchief epicardium myocardium endocardium These layers are girdled by the pericardium, a thin external  filling guarding your heart. There are 4 chambers that make up the heart – 2 on the left side and 2 on the right. The 2 small upper chambers are the gallerias. The 2 larger lower chambers are the ventricles. These left and right sides of the heart are separated by a wall of muscle called the septum. Circulatory system Your heart pumps blood around the body all the time- about 5 litres( 8 pints) of it. This is called  rotation. Your heart, blood and blood vessels together make up your cardiovascular system( or heart and circulatory system). The right side of the heart receives blood that's low in oxygen because ultimate has been used up by the brain and body. It pumps this to your lungs, where it picks up a fresh force of oxygen. The blood also returns to the left side of the heart, ready to be pumped back out to the brain and the rest of your body. Blood vessels Your blood is pumped around your body through a network of blood vessels  highways – they carry oxygen-rich blood from your heart to all corridor of your body, getting lower as they get further down from the heart capillaries – they connect the  lowest  highways to the  lowest modes, and help change water, oxygen, carbon dioxide and other nutrients and waste substances between the blood and the apkins around them modes – they carry blood, lacking in oxygen, back towards your heart, and get bigger as they get nearer your heart Blood vessels are suitable to widen or narrow depending on how important blood each part of your body requires. This action is  incompletely controlled by hormones. gates Your heart has 4 gates aortic  incline – on the left side mitral  incline – on the left side pulmonary  incline – on the right side tricuspid  incline – on the right side These act like gates, keeping the blood moving in the right direction. Electrical system For your heart to keep pumping regularly, it needs electrical signals which are transferred to the heart muscle telling it when to contract and relax. The electrical signal starts in the right yard where your heart’s natural trendsetter( the sino – atrial knot) is. This signal crosses the gallerias, making them contract. Blood is pumped through the gates into the ventricles. Where the gallerias meet the ventricles, there's an area of special cells( called the atrio- ventricular knot) which pass the electrical signals throughout your heart muscle by a system of electrical pathways, known as the conducting system. The muscles of the ventricles also contract, and blood is pumped through the pulmonary and aortic gates into the main  highways. The heart’s natural ‘ trendsetter ’( the sino- atrial knot) produces another electrical signal, and the cycle starts again. Blood pressure Blood pressure is the dimension of the pressure within the  highways. It plays a vital part in the way your heart delivers fresh blood to all your blood vessels. For blood to travel throughout your body snappily enough, it has to be under pressure. This is created by the relationship between 3 goods your heart’s pumping action the size and stretchiness of your blood vessels the  density of the blood itself One  shake is a single cycle in which your heart contracts and relaxes to pump blood. At rest, the normal heart beats roughly 60 to 100 times every  nanosecond, and it increases when you exercise. To  insure an respectable blood force around your body, the 4 chambers of your heart have to pump regularly and in the right sequence. There are 2 phases to your heart’s pumping cycle systole – this is when your heart contracts, pushing blood out of the chambers diastole – this is the period between condensation when the muscle of your heart( myocardium) relaxes and the chambers fill with blood