The Circulatory System Essays - Muscular System, Angiology

The Circulatory System Essays - Muscular System, Angiology The Circulatory System Forwards and backwards to the right and are at the same level of the fifth to eight dorsal vertebrae. The apex of the heart points downwards and forwards to the left and corresponds to the space between the fifth and sixth ribs. However, in thin people, the hearts apex may be pointing more downwards than to the left. Its atrial border corresponds to a line drawn across the sternum on a level with the upper border of the third costal cartilage. Its apex corresponds to a line drawn across the lower end of the same bone. Its upper surface is rounded and convex, directed upwards and forwards, which is formed mainly by the right ventricle and a part of the left ventricle. The back surface of the heart is flattened and rests upon the diaphragm. Of its two borders, the right is the longest and thinnest, the left is shorter but thicker and round. The muscles that make up the heart are known as cardiac muscles. Cardiac muscle only exists in the heart, not like skeletel muscle which is found in many parts of the body. Cardiac muscle fibers possess striations that are typical of skeletel muscle. However, they only respond to the autonomic nervous system and electrical commands that are generated from the heart. Skeletel muscle may have many nuclei, but cardiac muscle only has one nucleus. As well, cardiac muscle is very small compared to the larger skeletel muscle. As fitting with its duty, cardiac muscle has many mitochondria to convert food into energy faster than other muscles. Cardiac muscles communicate between junctions that are laid down between the muscles. They are called intercalated disks. Along certain points of the disks, cell membranes fuse together. The electrical current required to cause the muscles to contract pass through the cells easily and the adjoining cells will respond as well due to the intercalated disks. The cardiac muscle is really a large number of cells working together that function to act as a single cell. There are many proteins that give cardiac, as well as other muscles, to contract. Thin bundles of protein called myofibrils run the length of each fiber. Within the myofibrils are filaments (tiny threads of protein) that are arranged in a repeating pattern called a sarcomere. The filaments in each sacromere are made up of the proteins actin and myosin. Two clusters of actin are set in each end of the sacromere stretch towards the centre but do not touch. There are continuos threads of myosin located at the end of the sarcomere. The contraction can occur because of the region where the actin and myosin over lap each other. Small hooks on the myosin binds to the actin filaments and pull towards the centre of the sarcomere. This happens through the rapid ratchet-like actions of the myosin and actin pulling together. When the sarcomere pulls together, the fiber contracts and so does the muscle. In order for this to occur again, the sarcomere must be stretched out, which is caused by the blood re-entering the heart, expanding it. In an adult, the heart measures about five inches in length, three and a half inches in the broadest part of its horizontal diameter, and two and a half inches in its posterior. The average weight in the males is from ten to twelve ounces. In the female, the average weight is eight to ten ounces. The heart will continue to grow in size up to old age. This growth is more obvious in men than in women. The heart is subdivided by a muscle called the septum into two halves, which are named right and left according to their position. A muscle divides each half into two cavities. The upper cavity on each side is called the atria or auricle, and the lower side is called the ventricle. The right atrium and ventricle form the venous side of the heart. Dark venous blood is pumped into the right atrium from the entire body by the superior vena cava(SVC) and inferior vena cava (IVC), and the coronary sinus. From the right atrium, the blood passes into the right ventricle and from the right ventricle, through the

Dark Matter and a Distant Supernova Make an Eerie Cross

Dark Matter and a Distant Supernova Make an Eerie Cross A long time ago, in a galaxy far, far away...a massive star exploded. That cataclysm created an object called a supernova  (similar to the one we call the Crab Nebula). At the time this ancient star died, own galaxy, the Milky Way, was just starting to form. The Sun didnt even exist yet. Nor did the planets. The birth of our solar system still more than five billion years in the future. Light Echoes and Gravitational Influences The light from that long-ago explosion sped across space, carrying information about the star and its catastrophic death. ​Now, about 9 billion years later, astronomers have a remarkable view of the event. It shows up in four images of the supernova created by a gravitational lens created by a galaxy cluster. The cluster itself consists of a giant foreground elliptical galaxy collected together with other galaxies. All of them are embedded in a clump of  Ã¢â‚¬â€¹dark matter. The combined gravitational pull of the galaxies plus the gravity of dark matter distorts light from more distant objects as it passes through. It actually shifts the direction of the lights travel slightly, and smears the image we get of those distant objects. In this case, the light from the supernova traveled by four different paths through the cluster. The resulting images we see here from Earth form a cross-shaped pattern called an Einstein Cross (named after physicist Albert Einstein). The scene was imaged by the Hubble Space Telescope. The light of each image arrived at the telescope at   a slightly different time - within days or weeks of each other. This is a clear indication that each image is the result of a different path the light took through the galaxy cluster and its dark matter shell. Astronomers study that light to learn more about the action of the distant supernova and the characteristics of the galaxy in which it existed.   How Does this Work? The light streaming from the supernova and the paths it takes are analogous to several trains that leave a station at the same time, all traveling at the same speed and bound for the same final destination. However, imagine each train goes on a different route, and the distance for each one is not the same. Some trains travel over hills. Others go through valleys, and still others make their way around mountains. Because the trains travel over different track lengths across different terrain, they do not arrive at their destination at the same time. Similarly, the supernova images do not appear at the same time because some of the light is delayed by traveling around bends created by the gravity of dense dark matter in the intervening galaxy cluster. The time delays between the arrival of each images light tell astronomers something about the arrangement of the dark matter around the galaxies in the cluster. So, in a sense, the light from the supernova is acting like a candle in the dark. It helps astronomers map the amount and distribution of dark matter in the galaxy cluster. The cluster itself lies some 5 billion light-years from us, and the supernova is another 4 billion light-years beyond that. By studying the delays between the times that the different images reach Earth, astronomers can glean clues about the type of warped-space terrain the supernova’s light had to travel through. Is it clumpy? How clumpy?   How much is there?   Answers to these questions arent quite ready yet. In particular, the appearance of the supernova images could change over the next few years. Thats because light from the supernova continues to stream through the cluster and encounter other parts of the dark matter cloud surrounding the galaxies.    In addition to the Hubble Space Telescopes observations of this unique lensed supernova, astronomers also used the W.M. Keck telescope in Hawaii to do further observations and measurements of the supernova host galaxy distance. That information will give further clues into conditions in the galaxy as it existed in the early universe.