The cardiovascular system Assignment Example | Topics and Well Written Essays - 1500 words

The cardiovascular system - Assignment Example Consequently, blood goes to both directions in the body for each pump. The four major chambers of the heart are; the left atrium, left ventricle right atrium, and right ventricle. The deoxygenated blood that is from the body is usually pumped into the right ventricle and the right atrium through to the lungs (Evans & Sutton 2012, p. 13). On the other hand, from the lungs, the oxygenated blood is pumped into the left ventricle and the left atrium into the body. Both left and the right parts of the heart functions together to ensure the flow of blood all over the body. From the right part of the heart, blood enters the heart via the main vena cava and the inferior vena cover hence emptying the deoxygenated blood coming from the body into the right atrium. While the right atrium contracts, blood flows from the right atrium to the left ventricle via an opening called the tricuspid valve. However, when the ventricle is filled with blood, the valve shuts hence prevents the backward flow of blood into the atria as the ventricle contracts. Due to the contraction of the ventricle, the heart releases blood via the pulmonic valve then to the pulmonary artery and eventually to the lungs where it gets oxygenated (Evans & Sutton 2012, p. 34). On the left side of the heart, pulmonary vein empties the blood rich in oxygen from the lungs to the left atrium. Due to contraction of the left atrium, blood flows from the left atrium then into the left ventricl e via an opening called mitral valve. The valve then shuts once the ventricle is filled preventing the flow of blood backward. With the contraction of the ventricle, blood flows out of the heart via the aortic valve through aorta then into the body. The rhythmic contraction of the heart occurs spontaneously, even though the rate of contraction may be changed by the hormonal or nervous influences. For instance, the

USA in the 21st century Essay Example | Topics and Well Written Essays - 1250 words

USA in the 21st century - Essay Example Additionally, the development of nuclear weapons and the need to gain world wealth has necessitated many states to be more involved in war to show their might against other states. Many nations are struggling to survive in a world dominated by military power and technological development of nuclear weapons. Although, the nations claim existence of democracy and that international relations can be enhanced there are nations that advocate ruling the rest of the world through the wealth and military power. Any nation that tries to compete with the superpowers is attacked indirectly. Therefore, the 21st century world is likely to be dominated by wars in struggle for survival and supremacy. The 21st century is likely to be war prone because of the struggle for super powers among world nations. According to Mearshein, he came up with a number of assumptions that explain why the structure of international relations is made up of nations who have selfish gains for their own states rather than to the world as a whole1. As a result, the great power nations around the world seek for supremacy, maximum wealth, dominion over land and nuclear superiority. To gain their superpowers the great nations have embarked on â€Å"war, blackmail, bait and bleed, bloodletting, balancing and buck passing†2. Mearshein came up with a number of assumptions explaining paths nations pursue to become superpowers. The first reason is that the international relations is anarchic3. ... Even though states try to live in harmony, aggressiveness against another state can originate from nowhere leading to war. This therefore, has necessitated most states to stay alert and not to trust neighboring nations. Most nations strive for survival with diverse intentions in mind. The need for supremacy, wealth, military power and land has resulted to a number of cases of war. States that are continuing to grow in wealth than the superpowers are now involved in cold wars. States with nuclear weaponry mighty are also in disagreements with superpowers and wars may ensue any moment. The struggle is therefore, real with the super power nations wanting to remain superior, and other nations struggling to get to the level of super power nations. The 21st century is likely to be affected by war, because of the existence of fear in international politics. According to Tang, many states are faced with fear of the future5. Therefore, most states are striving for survival against the fear by leading in wars and being informed of what is happening in other states. States around the world are uncertain of the intentions of other nations. They do not know if they want to attack or if they are developing nuclear weapons. Thus, the uncertainty results to most states being alert and developing their military base, to ensure they are ready for any attacks that may take place. Moreover, most states have their own goals in ensuring they attain supremacy over other states. Nations only work together when they are faced with a common enemy. According to Tang, in international theory cooperation among nation state is practiced when the nations are facing a common enemy. Each state has its own personal gains when they advocate to be involved in war6. The