The heart

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The heart is a muscular organ and is responsible for pumping blood around the body, and on average the human heart beats at 72 beats per minute. When looking at the heart (see diagram below) it is important to remember that the left and right side are reversed (due to the way we are looking at it). The right side of the heart deals with deoxygenated blood and pumps it into the lungs. The left side of the heart deals with oxygenated blood, and pumps it around the entire body. The lower chambers of the heart are known as the ventricles and they are more muscular and stronger than the upper chambers, known as the atria. This is because a large volume of blood is pumped from the ventricles up through the atria and around the body. It is important to maintain a healthy heart, as it reduces the risk of developing high blood pressure and cholesterol levels, as well as developing heart disease.

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By eating healthy and doing regular exercise we are able to reduce these factors as well as reducing stress levels too. The heart is an organ that it part of the cardiovascular system. It is located between the lungs, behind the sternum and is approximately the size of a fist. The heart is protected by a membrane called the pericardium which surrounds the heart and secretes a fluid that reduces friction when the heart beats. The atria's job is to receive blood and the ventricles job is to be filled with blood and send it to everywhere in the body. There are three layers which make up the wall of the heart. The outer layer is epithelial tissue, the middle layer is cardiac muscle and the inner layer is connective tissue. Deoxygenated blood is pumped from the right ventricle and into the lungs, where the blood is regenerated with oxygen and returned through the pulmonary vein. The following explains the hearts role and internal structure in more detail.

There are four chambers in the heart, the top of the heart has a right and left atrium and the lower part of the heart has a right and left ventricle. These are the two major pumps of the heart. The right side of the heart deals with blood that is low in oxygen, commonly referred to as being blue in and being known as deoxygenated blood (see diagram 1). The deoxygenated blood enters the right side of the heart via the vena cava situated at the top. The inferior vena cava returns blood from the rest of the body and the superior vena cave returns blood from the head and arms. When the heart relaxes, it causes the right atrium to fill with blood. The atria then contract causing pressure to rise and the right atria ventricular valve to open. Blood from the right atrium is squeezed into the right ventricle and if listened to with a stethoscope the valve makes a 'blub' sound. The valves snap shut to prevent any back flow of the blood. When the right ventricle contracts, it forces the blood through the semi lunar valve into the pulmonary arteries, and into the lungs. This is where gaseous exchange takes place, the deoxygenated blood has carbon dioxide removed by the expelling of the lungs, also known as respiration, and the blood is re-absorbed with oxygen.

The heart contains four very important valves, the aortic, tricuspid, mitral and pulmonic valve. They ensure that the blood flows through the heart and body in one circuit, preventing any backflow. However, instead of the valves snapping shut, they can partially close, causing blood to flow back through to the chambers. This is known as having a leaky valve or a heart murmur. If this occurs it results in the heart being less efficient, by not allowing all the blood flow around the body. By using a stethoscope, you are able to hear the opening and snapping shut of the valves, commonly heard as being heard as lub dub. Our blood pressure is caused by the contraction of the heart and muscles that surround the blood vessels. Normal blood pressure is measured approximately at 120/80mh. The first measurement (120mmHg) is known as systolic pressure, this is where the heart contracts and blood is pumped out of the heart. The second measurement (80mmHg) is known as diastolic pressure, this is where the heart relaxes and blood fills the ventricles.

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The circulatory systems works with many other systems in the body such as the endocrine system, which is responsible for secreting hormones from various glands such as the pituitary, thyroid and adrenal glands. The endocrine system releases these hormones into the blood stream and has a direct influence on the body's metabolism. It also maintains a level balance of other substances in the body such as blood sugar, blood pH and water balance. Another system that also works in conjunction with the circulatory and endocrine system is the nervous system it adapts to any changes and reactions that may occur internally or externally, as well as involving the central nervous system (CNS) and the peripheral nervous system (PNS) (http://medical-dictionary.thefreedictionary.com/system). The circulatory role is to maintain the neurons with a supply or nutrients and oxygen to allow the involvement of signal transmission (wikipedia.co.uk)

When exercising, the heart beats faster as more oxygen is required to be transported around the body to all the muscles involved. As well as this it also causes an increase in body temperature as well, as the body attempts to keep cool by vasodilatation. The more exercise that's is done on a regular basis the stronger the heart becomes, resulting in a larger heart and an ability to pump more blood through the body and more importantly reducing the risk of high blood pressure, high cholesterol, weight gain, heart disease, type 2 diabetes as well as joint and bone problems. Exercise helps burn off any unwanted fat that the body cannot be removed. By boosting energy levels, maintain bone strength and helping us to relax and therefore reduce stress levels; we are also helping to prevent strokes, some types of cancers as well as osteoporosis. Those who exercise more often and vigorously have a lower risk for heart disease. (healthcentral.com). The British Heart Foundation (BHF) states that by exercising we are able to control the previous risks, along with the combination exercise, should come healthy eating. This means eating five or more portions of fruit and vegetables per day, reducing the intake of fats, eating at least 2 portions of fish a week, and avoiding any extra added salt to food.

According to new research funded by the British Heart Foundation and published in the Journal of the American College of Cardiology (JACC), poor health habits are a key factor to those suffering from stress, which can result in an increased risk of heart disease. Stress is does not have a direct link with heart disease, but is known to have symptoms which may lead to it or contribute to it. For example, smoking, drinking alcohol or overeating are common ways to relieve stress, but are likely factors that can lead to heart problems sooner or later. By learning how to relax, regular exercise and avoiding stressful situations it can reduce any symptoms which may lead to heart disease, such as angina.