The Cardiac Cycle - Essay Example

Running head: The Cardiac cycle Student’s Name: Instructors’ Name: Course Code: Date of Submission: Introduction The cardiac cycle can be described as the events related to the flow or blood pressure taking place from the beginning of one heartbeat to another. It can also be described as the series of events that takes place when the heart beats. Cardiac cycle can be categorized into two major phases that include systole phase and diastole phase as argued by Heart (2001). Systole cycle takes place when there is contraction of heart ventricles resulting to highest pressures within circulation systems. Diastole in the moment between ventricular contractions when left and right ventricles relax and fill as argued by Heart (2001). A cardiac cycle is usually complete when the heart is filled with blood and then the blood is pumped out of the heart. In the cardiac cycle, blood pressure usually decreases and increases, correct pressure relationships depend on careful timing of contractions. The heart rate is usually used to refer to the cardiac cycle frequency. This essay will discuss and evaluate the cardiac cycle and some of the major aspects related with it. The essay will also discuss some of the ways in which the cardiac cycle can be monitored within the bodies. Phases of Cardiac cycle There are usually two phases involved in the cardiac cycle as stated earlier. They include diastole and systole phases according to Heart (2001). During the first diastole phase, the ventricles and atria are relaxed and the atrioventricular valves get open. The blood, which is de-oxygenated from inferior and superior vena cavae, gets into right atrium. The blood is allowed by open atrioventricular valves to get to the ventricles. The atria is triggered to contract by the SA node. The right atrium empties its contents into the right ventricle. It is tricuspid vavle that prevents the blood from getting back to right atrium. In the first systole phase, the left ventricle usually gets impulses and contracts. These impulses are produced by purkinje fibers which extend from the atrioventicular bundle according to Fredric & Judi (2008). The fibers carry out the function of relaying cardiac impulses to the cells of ventricles leading to their contraction. Atrioventricular valves close during this phase and the semilunar valves open allowing de-oxygenated blood to be pumped into the pulmonary artery as stated by Heart (2001). A pulmonary valve is present which prevents any blood from flowing back into the right ventricle. Blood is then carried to the lungs by a pulmonary artery. Here, blood becomes oxygenated and is returned by the pulmonary veins to the left atrium of the heart. The second diastole phase involves closing of the semilunar valves and opening of the antrioventicular ones. The left atrium is then filled with blood from the pulmonary veins. At the same time, blood from the venacava is also filling the right atrium. The Sinoatrial node contracts causing the atria to contract as well. The left atrium then empties the blood into the left ventricle of the heart. There is a mitral valve present which prevents the oxygenated blood from getting back into the left atrium as illustrated by Heart (2001). The second systole phase involves the closure of the semilunar valves and opening of the atrioventricular ones. Purkinje fibers transmit impulses to the left ventricle which leads to its contraction as stated by Arthur& John (2006). Blood that is rich in oxygen is then pumped into the aorta. Oxygenated blood is prevented from flowing back into the left ventricle by the aortic valve. The aorta the transports blood to the rest of the body while de-oxygenated blood is returned through the vena cava. The heart as an organ The heart is centrally located in the lower portion of the chest and consists of four chambers that include the right and left atria and the right and left ventricles. Its main role is to pump blood to all parts of the body. The ventricles are muscular chambers that push or pump the blood out of the heart. The right ventricle pumps blood to the heart through the pulmonary artery while the left ventricle pumps blood to the rest of the body. The left and right atria receive blood into the heart and empty it into the ventricles (Fredric & Judi 2008). The heart has four valves namely; tricuspid, pulmonic, mitral and aortic valves which keep the blood moving in the right direction within the heart. The chambers of the heart pump blood in series. The right side of the heart consists of the right ventricle, the pulmonary valve, the right atrium, the tricuspid valve and the pulmonary artery. Blood that is de-oxygenated returns to the heart and gets into the right atrium where it is stored until the right atrium contracts. After contraction of the right atrium, the tricuspid valve opens to allow the blood to enter into the right ventricle as argued by Fredric & Judi (2008). The right ventricle then contracts, and the pulmonary valve opens to allow blood to be propelled into the pulmonary artery. The pulmonary artery then carries the pumped blood into the lungs to get oxygenated. The blood is then transported back into the heart through the pulmonary vein. The blood enters the left atrium and stays there till the left atrium contracts. After contraction of the left atrium, the mitral valve opens in order to allow blood to flow into the left ventricle as argued by Fredric & Judi (2008). The left ventricle then contracts leading to the opening of the aortic valve. Blood is then pumped into the aorta which carries the oxygenated blood to the rest of the body. The pulmonary artery carries blood from the heart to the lungs. The blood transported by this vessel is usually de-oxygenated. Major arteries carry blood rich in oxygen to other parts of the body as argued by Fredric & Judi (2008). Veins on the other hand, transport blood to the heart. They can either be major veins otherwise known as vena cava or pulmonary veins. Major veins carry de-oxygenated blood from the body to the heart while the pulmonary vein transports oxygenated blood from the lungs to the heart. The heart organ has four chambers which serve their respective purposes. It has both the right atrium, left atrium and the left and right ventricle. The right atrium has both the superior and inferior vena cava that brings blood from other body parts to the heart as argued by Fredric & Judi (2008). Usually the superior and inferior vena cava transports deoxygenated blood. The superior vena cava supplies blood from the upper half of the body including the neck, head, and chest regions into the right atrium while the inferior vena cava supplies deoxygenated blood from the legs and the rest of the lower body into the right atrium as argued by Fredric & Judi (2008). Electrical impulses There are series of electrical impulses used to coordinate the cardiac cycle. These are produced by specialized cells of the heart found in atrioventricular node and sinoatrial node. The Sinoatrial node which is located on the wall of the right atrium acts as a pace maker for the heart. It controls the contraction of the atria during this the first diastole as illustrated by Arthur& John (2006). At the onset of the systolic phase, some special cardiac muscle fibers within the sino-atrial node (S-A node) contract. This usually sends some electrical signal propagated through the heart. When the atrium contracts, the right atrium empties the blood into the right ventricle. A valve known as the tricuspid valve is present and ensures that blood does not flow back into the right atrium as argued by Fredric & Judi (2008). The cardiac muscle has myocytes usually used to start their own contraction without the assistance of external nerves except during special instances like when metabolic demand increases. The cardiac cycle usually involves transportation of blood from the heart to the lungs for oxygenation before blood can be brought back into the heart by the pulmonary vein to be pumped to the rest of the body. It takes into account the importance of various arties in ensuring that blood is transported at high pressure in order to reach all organs of the body. The cycle also takes into account the importance of capillaries in acting as sites for exchange of both nutrients and gases from the blood to the cells as stated by Arthur& John (2006). It also acts as a site whereby waste products and gases are transported from the cells to specific organs of the body that help in getting rid of waste. These include the lungs which carry out gas exchange by getting rid of carbon dioxide produced in the body and providing oxygen to be used by body cells. The kidneys also play a role in getting rid of waste material and re-absorption of useful substances from the blood. The cardiac cycle works together with other systems in the body to ensure that the body is maintained in good health. The flow of blood in atria-ventricular valves is usually in one direction as argued by Fredric & Judi (2008). The valves close to avoid backflow of the blood. In analyzing the cardiac cycle from the time blood is pumped from the heart to other body parts, it can be deduced that the cardiac cycle is efficient in that blood in different chambers of the heart does not mix. This ensures that the body is supplies with nutrition and that toxic wastes are gotten rid of. Monitoring the heart rate It is important for the heartbeat to be monitored in patients who have heart problems. A heart rate monitor measures the rate of heartbeat with respect to time and the record is kept for future reference. This in turn helps to check on the patient’s health and prevent complications that may result to heart attacks. Phonocardiograph is an instrument that is used to detect sounds that are produced by the pumping mechanism of the heart as illustrated by Arthur & John (2006). An electronic stethoscope has been developed which has a microphone helping in amplifying sounds made by the heart and therefore detecting abnormalities present. Closure of the tricuspid and mitral valve make up the first sound while the second is caused by slight back flow of the blood as the valves close. The third and fourth sounds are usually lower in intensity. The third sound is due to flow of blood into the ventricles while the fourth is as a result of contraction of the atria. The third and fourth sounds are normally inaudible in adults but can be heard in children. Conclusion In conclusion, the cardiac cycle is the most important cycle in the body. This is because it controls all other cycles in the body that it would be impossible for any organ or system within the body to function without blood supply. The sequence in which the heart pumps the blood is known as the cardiac cycle. The four chambers of the heart are well adapted in that they have valves that prevent backflow of blood and hence, act efficiently in the process of cardiac cycle. Separation of the chambers also ensures that the blood does not mix in the process of cardiac cycle. It is important to note that the arteries are thin in order to maintain the blood pressure while the veins have valves to ensure blood does not flow backwards. In reality, the cardiac cycle can be illustrated as the coordinated cycle of events that occurs simultaneously on both left systemic circuit and right pulmonary circuit of the heart. References Arthur, C & John, E 2006, Textbook of medical physiology, 11th edn. New York, Elsevier Saunders. Martini, F & Judi, N 2008, Fundamentals of anatomy and physiology, 8th ed., London, Benjamin Cummings. Heart, L, 2001, Abstracts of the 49th annual scientific meting of the cardiac society of Australia and New Zealand. Vol. 10, Issue 3, pp. 78-90. Read More

The fibers carry out the function of relaying cardiac impulses to the cells of ventricles leading to their contraction. Atrioventricular valves close during this phase and the semilunar valves open allowing de-oxygenated blood to be pumped into the pulmonary artery as stated by Heart (2001). A pulmonary valve is present which prevents any blood from flowing back into the right ventricle. Blood is then carried to the lungs by a pulmonary artery. Here, blood becomes oxygenated and is returned by the pulmonary veins to the left atrium of the heart.

The second diastole phase involves closing of the semilunar valves and opening of the antrioventicular ones. The left atrium is then filled with blood from the pulmonary veins. At the same time, blood from the venacava is also filling the right atrium. The Sinoatrial node contracts causing the atria to contract as well. The left atrium then empties the blood into the left ventricle of the heart. There is a mitral valve present which prevents the oxygenated blood from getting back into the left atrium as illustrated by Heart (2001).

The second systole phase involves the closure of the semilunar valves and opening of the atrioventricular ones. Purkinje fibers transmit impulses to the left ventricle which leads to its contraction as stated by Arthur& John (2006). Blood that is rich in oxygen is then pumped into the aorta. Oxygenated blood is prevented from flowing back into the left ventricle by the aortic valve. The aorta the transports blood to the rest of the body while de-oxygenated blood is returned through the vena cava.

The heart as an organ The heart is centrally located in the lower portion of the chest and consists of four chambers that include the right and left atria and the right and left ventricles. Its main role is to pump blood to all parts of the body. The ventricles are muscular chambers that push or pump the blood out of the heart. The right ventricle pumps blood to the heart through the pulmonary artery while the left ventricle pumps blood to the rest of the body. The left and right atria receive blood into the heart and empty it into the ventricles (Fredric & Judi 2008).

The heart has four valves namely; tricuspid, pulmonic, mitral and aortic valves which keep the blood moving in the right direction within the heart. The chambers of the heart pump blood in series. The right side of the heart consists of the right ventricle, the pulmonary valve, the right atrium, the tricuspid valve and the pulmonary artery. Blood that is de-oxygenated returns to the heart and gets into the right atrium where it is stored until the right atrium contracts. After contraction of the right atrium, the tricuspid valve opens to allow the blood to enter into the right ventricle as argued by Fredric & Judi (2008).

The right ventricle then contracts, and the pulmonary valve opens to allow blood to be propelled into the pulmonary artery. The pulmonary artery then carries the pumped blood into the lungs to get oxygenated. The blood is then transported back into the heart through the pulmonary vein. The blood enters the left atrium and stays there till the left atrium contracts. After contraction of the left atrium, the mitral valve opens in order to allow blood to flow into the left ventricle as argued by Fredric & Judi (2008).

The left ventricle then contracts leading to the opening of the aortic valve. Blood is then pumped into the aorta which carries the oxygenated blood to the rest of the body. The pulmonary artery carries blood from the heart to the lungs. The blood transported by this vessel is usually de-oxygenated. Major arteries carry blood rich in oxygen to other parts of the body as argued by Fredric & Judi (2008). Veins on the other hand, transport blood to the heart. They can either be major veins otherwise known as vena cava or pulmonary veins.

Major veins carry de-oxygenated blood from the body to the heart while the pulmonary vein transports oxygenated blood from the lungs to the heart.

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