The main function of the heart is to deliver blood and oxygen to all tissues. In order to understand the major diseases that affect the cardiovascular system, it is important to study the heart's basic anatomy and physiology. This paper addresses the basic principles of the structure and function of the heart.
The arterial supply of the heart is built from the right and left coronary arteries, which arise from the aorta.
The cardiac muscle is composed by specialized cells: cardiac myocytes. Kumar et al. (2005) describe five major components in the myocytes: cell membrane (sarcolemma) and T-tubules; sarcoplasmic reticulum; contractile elements; mitochondria; and nucleus. The sarcolemma and T-tubules enable impulse conductions, and the sarcoplasmic reticulum is a calcium reservoir needed for contraction. Mitochondria are crucial components, since they are involved in cardiac contraction by providing a constant supply of ATP to the sarcomeres. Mitochondria are abundant in cardiac tissue, constituting 20% to 40% of cellular volume in energy-demanding zones (Marin-Garcia 2005).
Cardiac muscle is composed of sarcomeres, which are the contractile units with an arrangement of thin and thick myofilaments. The myocytes are composed of many parallel myofilaments arrays of sarcomeres in series, which are responsible for the striated appearance (Kumar 2005). Thin filaments are composed of various proteins named actin, tropomyosin, and troponin. Myosin is the thick filament, and possesses the cross-bridges that can attach to the actin. Au (2004) has described the various components of the sarcomere in great detail. Since cross-bridges possess ATPase activity, contraction may be explained as a continuous cycling of cross-bridges. Moreover, cardiac muscle fibers are joined together by junctional complexes called intercalated discs (Dunn 2004), so that the action potential is spread.
The role of Calcium
Calcium (Ca2+) regulates mechanical contractions and Vandenboom et al. (2005) have shown that "cross-bridge attachment increases thin filament activation dynamically and that this increase is proportional to the level of activation first established by Ca2+"; during membrane depolarization, a small amount of Ca2+ enters through specialized channels, and the influx triggers calcium release of the sarcoplasmic reticulum. Intracellular calcium binds to troponin C, which induces activation of the myofilaments and muscle contraction. Relaxation is initiated by dissociation of Ca2+ from troponin C, followed by its reuptake into the sarcoplasmic reticulum and removal through sodium/calcium exchangers (Chakraborti et al. 2007).
Structure and Function
Ventricular muscle contracts during systole and relaxes during diastole. The sarcomere length and sliding mechanism has been described by various researchers (Pollack et al 2005). The Frank-Starling mechanism depicts the relationship between structural components of the heart and its function: shorter sarcomeres have considerable overlap of actin and myosin filaments, reducing its contractile force, whereas longer lengths enhance contractility. In a normal heart, moderate dilation increases the subsequent force of contraction. With progressive dilation, however, there is a point at which effective overlap of filaments is reduced, and the force of contraction is reduced (Kumar 2005). The clinical consequences of ...
Cite this document
(“The Heart Essay Example | Topics and Well Written Essays - 1000 words”, n.d.)
Retrieved from https://studentshare.net/science/299233-the-heart
(The Heart Essay Example | Topics and Well Written Essays - 1000 Words)
“The Heart Essay Example | Topics and Well Written Essays - 1000 Words”, n.d. https://studentshare.net/science/299233-the-heart.
He conquered Congo, because of its natural resources, especially rubber and ivory. This story focuses on the slave trade and the oppressive conditions in Congo. Marlow’s mission is to bring back Kurtz, a company employee, who failed to come back. Marlow’s journey to the Inner Station exposed realities about the evils of European imperialism and humanity.
He searched for Kurtz and encountered a man who took him to a realization that he never expected. The novel depicts imperialism in complex ways. Perhaps the clearest illustration of imperialism was when Marlow reached the outer station. Surrounded by slave workers, with large holes filled with broken machines around him, he said that “imperialism is really composed of the bodies he had seen”.
Conrad, as a seaman who worked for the British merchant marines, often journeyed into the so-called uncivilized parts of the world. One interpretation of the heart of darkness is represented by these dark places of which men of the outside knew little-especially the continent of Africa, which was known as the Dark Continent.
As long as it can be remembered, the heart symbol as we know it today has existed and appeared in different forms and places. It is one of the constantly recurring symbols from prehistoric times. The heart shape is considered to be a combination of ideograms (“Symbol 20:18”).
And so Mexico-born writer Alma Guillermoprieto tells us simply and bluntly that she wrote her book, "The heart that bleeds Latin America Now," with the "conviction that Latin America has its own independent life."
What emerges is a collection of essays that take readers through the sad psychological and political battles of Colombians, Cubans and Mexicans--all from countries that shape U.S.
Catholicism looks upon these religious authorities as the mediation between God and a devout Christian. Perceptibly at the heart of Catholicism lies a rigid sense of institutionalism, a strong commitment to the religious
d from the right atrium and pumps it to the lungs, where it is loaded with oxygen (Hall, 2011).The left atrium receives oxygenated blood from the lungs and pumps it to the left ventricle. The left ventricle (the strongest chamber) pumps oxygen-rich blood to the rest of the
They also acknowledge the fact that biblical traditions have contributed to wisdom in the society to a large extent. It is through this wisdom that people have become concerned about the moral problems
3 Pages(750 words)Essay
GOT A TRICKY QUESTION? RECEIVE AN ANSWER FROM STUDENTS LIKE YOU!
Let us find you another Essay on topic The Heart for FREE!