Heart and Cardiac Muscle Essay

What is the aggregate?The nitty-gritty is the organ that supplies livestock and oxygen to all separate of the body. It is about the size of a clenched fist, weighs about 10.5 ounces and is shaped like a cone. The heart is hardened in the chest cavity just posterior to the breastbone, between the lungs and superior to the diaphragm. The heart is surrounded by a fluid filled sac called the pericardium. Blood is pumped away from the heart through arteries and re licks to the heart through veins. The major artery of the body is the aorta and the major veins of the body ar the vena cavae.Chambers of the messageThe heart is divided by a partition or septum into two halves. The halves are in turn divided into chambers. The upper two chambers of the heart are called atria and the lower two chambers are calledventricles. The atria receive blood returning to the heart from the body and the ventricles pump blood from the heart to the body. Valves allow blood to flow in one direction betw een the chambers of the heart.The Heart WallThe heart is self-possessed of cardiac muscular tissue which enable the heart to contract and allow the synchronization of the heart beat. The heart surround is divided into three layers the epicardium, myocardium, and endocardium.* Epicardium outer protective layer of the heart.* Myocardium muscular middle layer protect of the heart.* Endocardium inner layer of the heart that is continuous with the inner lining of blood* cardiac Conduction* Cardiac conduction is the rate at which the heart conducts electric impulses. Cardiac muscle cells contract spontaneously and are coordinated by nodal tissue, specifically the sinoatrial lymph node. There are other factors that influence heart rate as well. These include endocrine hormones, body temperature and exercise.* Cardiac Cycle* The cardiac cycle is the sequence of events that occur when the heart beats. There are two phases of this cycle which are the diastole and systole phases. During the diastole phase, the atria and ventricles are relaxed and blood flows into the atria and ventricles. In the systole phase, the ventricles contract move blood to the rest of the body.A heartbeat is a two-part pumping action that takes about a second. As bloodcollects in the upper chambers (the safe and left over(p) atria), the hearts natural pacemaker (the SA node) sends out an electrical signal that causes the atria to contract. This contraction pushes blood through the tricuspid and mitral valves into the resting lower chambers (the right and left ventricles). This part of the two-part pumping phase (the longer of the two) is called diastole. The second part of the pumping phase begins when the ventricles are full of blood. The electrical signals from the SA node travel along a pathway of cells to the ventricles, causing them to contract. This is called systole.As the tricuspid and mitral valves shut implike to prevent a back flow of blood, the pulmonary and aortic valves a re pushed open. While blood is pushed from the right ventricle into the lungs to pick up oxygen, oxygen-rich blood flows from the left ventricle to the heart and other parts of the body. aft(prenominal) blood moves into the pulmonary artery and the aorta, the ventricles relax, and the pulmonary and aortic valves close. The lower pressure in the ventricles causes the tricuspid and mitral valves to open, and the cycle begins again.This series of contractions is repeated over and over again, increasing during times of exertion and decreasing plot you are at rest. The heart normally beats about 60 to 80 times a minute when you are at rest, but this can vary. As you get older, your resting heart rate rises. Also, it is usually lower in people who are physically fit. Your heart does not work alone, though. Your brain tracks the conditions about youclimate, stress, and level of physical activityand adjusts your cardiovascular system to meet those needs. The human heart is a muscle desi gned to remain strong and reliable for a hundred years or longer. By reduction your risk factors for cardiovascular disease, you may help your heart stay healthy longer.