Electro Physiology of the Human Heart

Electro Physiology of the Human Heart Introduction This chapter is the first chapter in the thesis which gives introduction of the present study. The chapter defines electro physiology of human heart, blood circulation in both pulmonary and systemic in detail, the components in cardiovascular system and heart sounds. It explains in detail the generation of potential due to mechanical activity of human heart and sounds produced due to closure of valves during blood pumping from atrias to ventricles and to respective parts of the body. This chapter presents a detailed survey on literature focusing on different methods to measure and analyse ECG and PCG. Electricity plays an important role in medicine. The control and operation of nerves, muscles and organs are functioning by the electricity generated inside the body. The forces of muscles, the action of brain and all nerve signals to and from the brain are caused by the attraction and repulsion of electrical charges. Many electrical signals are generated to carry out the special functions of the body. These signals are the result of electrochemical action of certain type of cells. The best known signals are electrical potentials of nerve transmission and the electrical signals observed in electromyogram (EMG) of the muscle, the electrocardiogram (ECG) of the heart and the electroencephalogram (EEG) of the brain. One means of obtaining diagnostic information about muscles, heart and brain are to measure their electrical activity. The record of the potential from muscles during movement of is called the electromyogram (EMG). The rhythmical action of the heart is controlled by an electrical signal initiated by spontaneous stimulation of pacemaker cells located at apex of the right atrium i.e. sinoatrial node (SA node). The recording of hearts potentials on skin is called electrocardiogram (ECG). The recording of the electric signals due to electrical activity of neurons in the cortex of the brain is called electroencephalogram (EEG). The present study is to study the electrical activity of heart during its mechanical vibrations. The primary step in investigations of physiological systems requires the appropriate sensors to transducer the phenomenon of interest into a measurable electric signal. The field of biomedical has advanced to the stage of practical application of signal processing and pattern analysis techniques for efficient and improved non- invasive diagnosis. 1.1 Physiology of Heart and Vascular System The analysis of variability in cardiovascular signals is applied widely and many experimental setups were put forward. Spontaneous fluctuations can be observed in cardiovascular function, such as heart rate and blood pressure, even when the environmental parameters are maintained at a constant level as possible and no perturbations influences can be identified. The observations of heart rate fluctuations is related to various cardiovascular disorders, the analysis of heart rate variability has become widely used tool in the assessment of the regulation of heart rate behavior (Timo Makikallo 1998). The study of cyclic variations of heart rate plays an important role in the assessment of both physiological and clinical aspects (Narayana Dutt Krishnan 2000). The heart is actually two separate pumps. A right heart that pumps the blood through the lungs and left heart pumps the blood through the peripheral organs. Each of these composed of atrium and ventricle. Atrium receives the blood and pumps into ventricles. Ventricles supply the main force that circulates the blood either through pulmonary circulation by the right ventricle or through the systemic circulation by the left ventricle(Fig 1.1) The blood, blood vessels and heart make up the cardiovascular system (CVS). The blood and its supply of oxygen are so important to the body that the heart is the first major organ to develop in the embryo. The mechanism in the heart provides cardiac rhythmcity and transmits action potentials through the heart muscle to cause the hearts rhythmical beat. The cardiac event that occurs from the beginning of the next are called the cardiac cycle. Each cycle is initiated by spontaneous generation of an action potential in the Sino atrious node or Sinus node. The cardiac cycle consists of a period of relaxation called diastole, during which the heart fills with blood fallowed by a period of contraction called systole together is known as a beat. The heart is composed of three major types of cardiac muscle; atrial muscle, ventricular muscle and specialized excitatory and conductive muscle fibers. Cardiac muscle is a syncytium of many heart muscle cells which are interconnected with intercalated discs which are of actually cell membranes separates cardiac muscle cells from one another and offers low resistance to ions to diffuse through cells. If one of these cells is excited, the action potential spreads to all of them. The heart is composed of two syncytiums the atrial syncytium that consists of walls of two atria and ventricular syncytium consists of the walls of two ventricles. The atria are separated from the ventricles by tissue that surrounds the atrio-ventricular valvular openings. Potentials are conducted from atrial syncytium into ventricular syncytium through the specialized conductive system called A-V bundle a bundle of conductive fibers. The division of the muscle of the heart into two functional syncytiums allows the atria to contract a short time ahead of ventricular contraction, which is important for effective heart pumping through lungs and peripheral organs. Another importance of the system is that it allows all portions of the ventricles to contract almost simultaneously, which is essential for most effective pressure generation in the ventricular chambers The cardiac cells present in the heart tissue are individually surrounded with an insulating membrane (supporting a potential mV) containing selective permeable ionic channels. The currents through these channels interact with the membrane potential to regulate the activity of the cell. The flow of various ions (Na,K,Ca etc) through out the cardiac tissue is responsible for the propagation of the electrical waves through tissue in turn provides the driving force behind the hearts mechanical contraction and its ability to pump blood through the body. 1.2. Components of Heart The heart is a conical, hollow muscular organ placed obliquely behind the body of the sternum and adjoining parts of the body of the costal cartilages, so that 1/3 rd of it lies right and 2/3 rd to the left of the median plane. The heart measures about 12x9cm and weighs 300 gm in males and 250 gm in females. The human heart has four chambers as shown in fig 1.2. The upper two chambers, the right and left atria are receiving chambers of blood. Atria collects venous blood from the body and about 75% of the blood flows directly into the ventricle even before atrial contraction. The atrial contraction causes an additional 25% filling the ventricles. The hearts lower chambers right and left ventricles are the powerful pumping chambers. The right and left sides of the heart are separated from each other by a wall of tissue .each side pumps blood through a different circuit of blood vessels. 1.2.1. The Right Atrium It is the right upper chamber of the heart receives venous blood from the whole body and pumps it to the right ventricle through right atrioventricular (tricuspid) opening. The chamber is elongated vertically, receiving the superior vena cava at the upper end and the inferior vena cava at the lower end. Deoxygenated blood from the whole body feeds into two large veins, the superior vena cava and inferior venecava, which empty into the right atrium of the heart and the same pumps to the right ventricle. 1.2.2. The Right Ventricle The right ventricle is a triangular chamber which receives blood from the right atrium and pumps it to the lungs through the pulmonary trunk and pulmonary arteries. Externally, the right ventricle has two surfaces anterior and inferior. The cavity of the right ventricle is crescent in section because of the forward bulge of inter ventricular septum. The wall of the right ventricle is thinner than that of left ventricle in a ratio 1:3. 1.2.3. The left atrium The left atrium forms the left 2/3 of the base of the heart and is a quadrangular chamber. It receives oxygenated blood from the lungs through four pulmonary veins and pumps it to the left ventricle through Mitral valve. 1.2.4. The Left Ventricle The left ventricle receives oxygenated blood from the left atrium and pumps it into the aorta, the bodys largest artery. Smaller arteries that branch off the aorta distribute blood to the various parts of the body. It forms the apex of the heart .The cavity of the left ventricle is circular in cross section and has the thickest walls nearly half an inch in an adult because it must work the hardest to propel blood to the farthest reaches of the body. 1.2.5. Valves of the Heart The valves of the heart maintain unidirectional flow of the blood and prevent blood from flowing backward in the heart i.e. the valves open easily in the direction of blood flow, but when blood pushes against the valves in the opposite direction the valves close. There are two pairs of valves in the heart i) atrio ventricular valves ii)Semilunar valves. Atrio-ventricular valves are located between the atria andventricles as shown figure. The right atrio-ventricular valve is formed from three cusps of tissue and is called Tricuspid valve. While the left atrio- ventricular valve has two cusps and is called Bicuspid or Mitral valve. Both valves are made up of a fibrous ring to which the cusps are connected .The cusps are flat and project into the ventricular cavity. The atrio- ventricular valves kept competent by active contraction of the papillary muscles. Semi lunar valves are located between the ventricles and arteries and each of them consist of three half moon shaped flaps of tissue. They are not attached to fibrous ring but are to the blood vessel .The right semi lunar valve between right ventricle and pulmonary artery is pulmonary valve and the valve between left ventricle and aorta is aortic valve .These valves are closed during ventricular diastole. 1.2.6. Superior Vena Cava It is about 7 cm long venous channel which receives blood from the upper half of the body and empties it to the right atrium like other large veins. It has no valves. 1.2.7. The Aorta The aorta is the great arterial trunk which receives oxygenated blood from the left ventricle and distribute it all parts of the body. 1.2.8. Myocardium It is the muscle tissue wraps around a scaffolding of tough connective tissue to form the walls of the heart chamber. The atria the receiving chambers of the heart have relatively thin walls than the ventricles, the pumping chambers. 1.2.9. Pericardium It is a tough, double layered sac which surrounds the heart. The inner layer of the pericardium is known as epicardium rests on top of the heart muscle. The outer layer is attached to the breast bone and other structures in the chest cavity and helps hold the heart in place. The space between the two layers of the pericardium filled with watery fluid which prevents these layers from rubbing against each other during heart beat. 1.2.10. Endocardium It is the inner surface of the hearts chambers lined with a thin white sheet of shiny tissue. The same type of tissue also lines the blood vessels forming continuous lining throughout the circulatory system. The lining helps blood to flow smoothly and prevents clotting of blood in the circulatory system. The heart is nourished not by blood passing through, but by the blood vessels also known as coronary arteries which encircle the heart like a crown. About 5% of the blood pumped to the body enters the coronary arteries, which branch from the left ventricle .Three main coronary arteries the right , the left circumflex and the left anterior descending nourish different regions of the heart muscle. From these three arteries small branches arise to provide a constant supply of oxygen. 1.3. A Detailed Description of Vascular System The cardio vascular system is concerned with the transport of blood and lymph through the body. It may be divided into four major components, the heart, the macro circular i.e. blood vessels arteries and veins, micro circular i.e. capillary and lymph vascular system i.e. water and other components of blood plasma. The cardio vascular system (CVS) controls the blood pressure by altering the heart rate and compliance i.e. elasticity of blood vessels. (Isla Gilmour 1995). 1.3.1. Arteries Arteries transport blood from high pressure to body tissues as their structure permits them to expand and contract under different pressures due to the presence of elastic fibers. The main artery of the heart is aorta, which starts from the left ventricle transporting oxygen and nutrients to all body tissues. The presence of elastic fiber enables the arteries to expand when each pulse of blood pumped by the heart and regains its original shape when tension is released. Like all blood vessels the inner layer of arteries is known as tunica intima, composed of a single layer of flattened endothelial cells fitted together to form a smooth, continuous tube. In large arteries the same layer is supported by thick band of elastic fibers. The middle layer is known as tunica media consisting of smooth muscle and elastic fibers. In very large arteries the outer layer is known as tunica adventitia also contains elastic fibers and connective tissue. 1.3.2. Veins Veins transport deoxygenated blood at low pressure toward the heart and act as reservoirs of different capacities to maintain a steady return of blood to heart. The veins of systemic circulation terminate at bodys largest veins superior and inferior vena cava which empty into the right atrium of the heart. The walls of the veins are thinner and contain little elastic fiber with greater internal diameter. These structural properties help them to stretch and store the blood. Since the pressure in veins is low some structural changes is needed to prevent blood from downward pull of gravity. The veins in the lower body contain special one-way valves prevent the accumulation of blood in the legs and feet. During exercise the muscles are in extremities, relaxing and contracting alternately squeezing the veins to force the blood upward towards the heart. The tunica media of veins is thinner and contain less elastic fiber and smooth muscle to function at low pressure and serving as reservoirs to maintain a steady return of blood to the heart. 1.3.3. Arterioles The functions of arterioles are to distribute the blood and pressure reducing valves. They play an important role in determining the blood pressure. The arterioles have smooth muscle in their walls and do not stretch rather act as pressure reducing valves between the arteries and capillaries. They prevent delicate capillaries from high pressure of blood in the arterial system. The degree of muscular tension in the walls of arterioles decides their internal diameter in turn changes the resistance of blood flow in arterioles. As they affect the blood pressure because they account for a large component of the peripheral resistance to blood flow. Blood pressure is the product of total peripheral resistance and cardiac output. 1.3.4. Venules The function of venules is to drain blood from the capillary bed into the venous system. 1.3.5. Capillaries Capillaries are very small blood vessels their diameter ranges from 4-15 ÃŽ ¼m. The sum of the diameters of all capillaries is significantly larger than that of the aorta which results in decrease of blood pressure and flow rate. Capillaries are composed of a single layer of flattened endothelial cells fitted together to form a continuous tube. This results in a very large surface to volume ratio. The low rate of blood and large surface area facilitate the functions are * Providing nutrients and oxygen to the surrounding tissue. * The absorption of nutrients, waste products and carbon dioxide and * The execution of waste products from the body. 1.3.6. Lymphatic Vessels Parts of the blood plasma will execute from the blood vessels into the surrounding tissues because of transport across the endothelium. The fluid entering tissues from capillaries adds to the interstitial fluid normally found in the tissue. The surplus of liquid will return to the circulation .Lymph vessels are dedicated to this unidirectional flow of liquid, the lymph. The lymph vessels can be divided into three types depending on their shape and size. Lymph Capillaries These are larger than blood capillaries and very irregular on shape. They begin as blind ending tubes in connective tissues. Lymph Collecting Vessels They appear almost similar to lymph capillaries but a bit large and form valves. The lymph is moved by the compression of the lymph vessels by surrounding tissues. The direction of lymph flow is determined by the valves Lymph Ducts They contain one or two layers of smooth muscle cells in their wall and form valves. The walls of lymph ducts are less elastic and during contractions contribute to the movement of lymph towards the heart in addition to the compression of the ducts by surrounding tissues. 1.3.7. Relations to Other Systems and Organs The heart and vascular system perform almost the same function to provide oxygen, nutrients and harmonic to the cells of the body tissue. They can be considered as one unit rather than two, because each is equipped to carry out half of that function. The vascular system is also closely related to the adrenergic receptors and the autonomic nervous system, which together control important aspects of its function. The alpha adrenergic receptors are the smooth muscle cells in arteries, veins, arterioles and venules. These receptors bind molecules released by cells of the autonomic nervous system and respond by contracting. 1.4. Blood Circulation -Systemic and Pulmonary The heart basically a double pump provides the force to circulate the blood through two major circulatory systems, the pulmonary circulation in the lungs and the systemic circulation is in organ system that transports substances to and fro from cells. The blood in normal individual circulates through one system into before being pumped by the other part of the heart to the second system. The heart is a muscle composed by cells containing small filaments of actin and myosin. These proteins interact in the sense of forming actomyosin during muscle contraction, thus leading to the main purpose of the heart: pumping the blood through the circulatory system (Manuel Duarte Ortigueiva 1959). The synchronous nature of contraction of heart results in the efficient pumping of blood through the pulmonic and systemic circulation (J.Olansen et al 2000). The circulatory system can be thought of as a closed loop circulation system with two pumps. One way valves keep the flow downward through the pumps. 1.4.1. Systemic Circulation The heart ejects oxygen rich blood under a pressure about 125 mm Hg from main pumping chamber left ventricle, through the largest artery the aorta. Subdivided into smaller arteries in turn divided into even smaller arteries called arterioles and finally into a very fine meshwork of vessels called the capillary bed. Capillaries permit to dissolve oxygen and nutrients from the blood to diffuse across the fluid, known as interstitial fluid that fills the gaps between the cells of tissues of organs. The dissolved oxygen and nutrients enter cells through interstitial fluid by diffusion across the cell membranes. Mean while carbon dioxide and other wastes leave the cell diffuse through the interstitial fluid, cross the capillary bed and enter the blood. The blood collects in small veins called venules gradually join together to form progressively larger veins. Finally the veins converge into two large veins, the superior vena cava and the inferior vena cava bringing blood from upper half and lower half of the body respectively. Both of these main veins join at the right atrium of the heart. 1.4.2. Pulmonary Circulation The deoxygenated blood returning from the organs and tissues of the body stored momentarily in the reservoir i.e. right atrium, during weak contraction (5 to 6 mm Hg) the blood pushed into the right ventricle. On the next ventricular contraction this blood is pumped at a pressure of about 25 mm Hg through pulmonary arteries to the capillary system in the lungs. At this site microscopic vessels pass adjacent to the alveoli or air sacs of the lung where it exchanges oxygen from the membrane to the blood and leaves carbon dioxide from blood to the same membrane. The freshly oxygenated blood then travels through the main veins from the lungs into the left reservoir i.e. left atrium of the heart. During weak arterial contraction (7 to 8 mm Hg) blood enters the left ventricle. On the next contraction of the left ventricle sends blood to the aorta and then to general circulation. On average a typical adult has about 4.5 lts of blood and each section of the heart pumps about 80 ml in each contraction. About 30 sec to 1 min is needed for the average red blood cell to complete a full circuit through both the pulmonary and systemic circulation. The blood volume is not uniformly divided between the pulmonary and systemic circulation. At any one time 80% of the blood is in the systemic circulation and 20% is in the pulmonary circulation. Of the blood in the systemic circulation about 15% is in the arteries, 10% is in the capillaries and 75% is in the veins. In the pulmonary circulation about 7% of the blood is in the pulmonary capillaries and the remaining is almost equally distributed between the pulmonary arteries and pulmonary veins. 1.4.3. Additional Functions In addition to oxygen, the circulatory system also transports nutrients derived from digested food to the body. These nutrients enter the blood from the walls of the intestine carries the nutrients to the liver for farther metabolic processing. The liver stores variety of substances such as sugar, fats and vitamins and releases glucose to the blood as needed. The liver also cleans the blood by removing waste products and toxins. After the blood is cleaned, enter the veins converge to form the large vein that joins the vena cava at right atrium. The circulatory system plays an important role * In regulating body temperature * To collect chemical messengers called hormones from hormone producing glands and transports to specific organs and tissues to regulate bodys rate of metabolism, growth, sexual development and other functions. * With immune system and coagulation system, the immune system is a complex system of many disease fighting white blood cells and anti bodies circulate in the blood and are transported to sites of infection. The coagulation system is composed of special proteins called clotting factors which circulate in the blood. When ever blood vessels are cut to torn, the coagulation system works rapidly to stop the bleeding by forming clots. Other organs support the circulatory system are the brain and the parts of nervous system constantly monitor blood circulation, sending signals to the heart or blood vessels to maintain constant blood pressure. New blood cells are produced in the bone marrow and old blood cells are broken down in the spleen, where iron and other minerals are recycled. Metabolic waste products are removed from the blood by kidneys which also screen the blood for excess salt and maintain blood pressure and to maintain blood pressure and to balance minerals and fluids of the body. 1.5. Heart Diseases Heart disease has become very common nowadays due to changes in life style. Many of these diseases are due to either increase the work load of heart or reduce the ability to work at normal rate. 1.5.1. Tachycardia There are many factors that are responsible for development of heart disease. One such factor is High blood pressure (Hypertension) which causes the muscle tension to increase in proportion to the pressure. A fast heart rate (Tachycardia) increases the work load. 1.5.2. Heart Attack The heart disease that causes most deaths is heart attack. A Heart attack is caused by blockage of one or more arteries to the heart muscle. During and after heart attack the ability of the heart is seriously impaired. Bed rest and giving oxygen reduces the work load on heart which increases the oxygen content in the blood so that blood pumped by the heart will be less. Alternate method to reduce risk of heart attack is the regular exercise program which opens alternate routes in cardiovascular system. 1.5.3. Congestive Heart Failure Another common disease is congestive heart failure which is due to enlarge in size of the heart reduce the ability for adequate blood circulation. Applying law of Laplace, if the radius of the heart is doubled, the tension of the heart muscle should be doubled which in turn reduces the efficiency of the heart muscle to maintain the same blood pressure. Since the heart is stretched it may not be able to produce sufficient force to maintain normal circulation. Stretched heart muscle is less efficient than the normal. It consumes much more O2 for the same amount of work. 1.5.4. Bradycardia Patients with inadequate electrical signal in the heart muscle will affect the work load of heart. The artrioventricular node i.e. between Atria and Ventricles is fatty and does not conduct electric signal and ventricle receive no signal from Atria, but being natural pacing centers which provide a pulse. The resulting heart rate is 30 beat/min i.e. Bradycardia results semi invalidism. 1.5.5. Pace Makers If hearts electrical signals are inadequate to stimulate heart muscles, artificial pace makers are available. To improve the quality of life of faulty atrioventricular nodes, artificial pacemakers are developed. The pacemaker contains a pulse generator that put out 72 beats / min. The pace maker is put just below the right collarbone. It lasts for 2 years and impervious to body fluids and do not cause tissue reaction. 1.5.6. Valve Defects Another heart disease is defective heart valves. These are of two types. 1) The valve either does or opens wide enough (stenosis). In stenosis large amount of work is to be done by heart to obstruct the narrow opening. 2) It does not close well enough (insufficiency).In insufficiency some of the pumped blood flows back and the amount of blood in circulation is reduced .Both types can be replaced by artificial valves. 1.5.7. Cardiovascular Diseases Aneurysm Some cardiovascular diseases involve the blood vessels. An aneurysm is a weakening of the wall of an artery which results increase in its diameter in turn increases the tension in the wall proportionately. If it is ruptured in brain, a type called Cerebrovascular accident (CVA). A more common blood vessel problem is the formation of sclerotic plaques on the walls the artery which causes turbulence in blood flow increases the blood velocity at that point with a decrease in wall pressure due to Bernoullis theorem. A Disease in Varicose Vein Veins with defective valves which allow the blood to flow backward become enlarged or dilated to form the varicose veins. During walking or other exercise, the contraction of the muscle forces the venous blood toward the heart called venous pump. At various points along the veins there are one way flaps or valves that prevent the blood from going back. If these valves become defective blood run backward and pool up in the vein becomes varicose. The standard treatment for varicose veins is surgical removal of the offending vessels. There are sufficient parallel veins to carry the blood back to the heart. Stiffness of RBC Membrane In some cases, mainly in smoking, the membrane of RBC s becomes stiff. There may not be normal flow of blood in the vascular system. Blood may become viscous leading to Thrombosis. 1.6. Electrophysiology of Heart The rhythmical action of the heart is considered by an electrical signal initiated by spontaneous stimulation of special muscle cells located in the upper right hand corner of the right atrium near the superior vena cava. This area is known as sino atrial node (Fig 1.5). Cardiac electro physiology is dedicated to the study of the electro chemical activity of the heart. Studies include electrical activation of individual cells as well as the system- level activation, which results in normal or abnormal heart rhythm. (J.Olansen et al 2000). The complex system found by the Autonomous Nervous System (ANS) and the heart is modeled as if it was a modulation system, where the first generates a signal that modulates a sequence of pulses which excite the heart (Manuel Duarte Ortigueira et al 1959 ). The sinus rhythm fluctuates around the mean heart rate, which is due to continuous alteration in the autonomous neural regulation i.e. sympathetic and parasympathetic balance. Periodic fluctuations found in heart rate originate from regulation related to respiration, blood pressure (baroreflex) and thermoregulation (Pauli Tikkanen 1999). Cells in the SA node generate their electrical signal more frequently than cells else where in the heart. These impulses spread rapidly through inter nodal pathways to Atrioventricular node (AV node). At this node the signal is delayed so that all muscle cells of the atria contract virtually in unison. Now the impulse conducts through fibrous connective tissue between atria and ventricles known as Atrio ventricular bundle (AV bundle). AV bundle conducts the signal through left and right bundles of Purkinje fibers which conduct the cardiac signal to all parts of the ventricles. 1.5.Fig. Electrophysiology of the heart. 1.6.1. Sinoatrial Node The sinoatrial node is a small, flattened ellipsoid strip of specialized muscle about 3 mm wide, 15 mm long and 1mm long located at the upper right hand corner of the right atrium immediately below and slightly lateral to the opening of the superior vena cava. The Sinoatrial (SA node), the atrioventricular (AV node) and the Purkinje system can be regarded as potential pacemaker tissues in heart. As the fastest depolarization impulse spreads through the conduction system to other pacemakers before they spontaneously depolarize, the sinoatrial node usually defines heart rate (Pali Tikkanen 1999 12). The sinus nodal fibers connect directly with the atrial muscle fibers, so that any action potential generates at the sinus node spreads immediately to the atrial muscle wall. For this reason Sinoatrial node is also known as pace maker of the heart. It generates the impulse at the rate of about 70/min and initiates the heart beat. However this rate may increase or decrease by the demand of blood supply to the body. Three types of membrane ion channels play an important role in causing the voltage charges the action potential. They are 1) fast sodium channels 2) slow calcium-sodium channels 3) potassium channels. As the ions move in muscle cells in fractions of second creates action potential at the Sinoatrial node. This can be observe

Fire Crackers :: essays research papers

Our Lives Versus Firecrackers   Ã‚  Ã‚  Ã‚  Ã‚  Bong! Bong! Bong! These are the typical sounds one would hear passing by a Chinatown around February of every year. Indeed, these are the sounds of firecrackers, which are distinctive features Chinese people use to welcome a new beginning on Chinese New Year. However, can anyone imagine how many people have died or have been injured by these explosive features? According to a report, a firecracker storage area in China caught fire which caused the death of forty-seven people. An event of happy celebration unfortunately ended up being a tragically one. This leaves a question that needs to be answered: Should people's lives be sacrificed in order to keep the tradition of New Year celebration?   Ã‚  Ã‚  Ã‚  Ã‚  Being a Chinese, I truely understand that Chinese New Year is the most important and most celebrated holiday for Chinese. In addition, firecracker displays are always the first event to be launched off as the New Year arrives. According to older generations, firecrackers are considered not only a sign of getting rid of the old and welcoming the new, but are also believed to be able to dispel the evils. As a result, Chinese families deem the activity as an important one. However, it seems like this tradition is kept at the expense Lee 2 of innocent people's lives.   Ã‚  Ã‚  Ã‚  Ã‚  In fact, firecrackers can lead to significant casualties if people don't use it appropriately. In recent years, firecrackers are bannedb in some states in America. There are a total of 11 states that ban all types of firecrackers while some states only allow few types of firecrackers. Most leniently states such as Louisiana, Mississippi, Alabama, and Florida still allow all types of firecrackers ( Essoyan; Los Angeles Time ). The administration of some states has refused to allow the setting off of firecrackers during Chinese New Year celebration because these state governments believe that these explosives are too dangerous. Moreover, firecrackers have also been banned in China, after the firecracker storage area explosion incident.   Ã‚  Ã‚  Ã‚  Ã‚  In addition to its explosiveness, firecrackers are hazardous to people's health and lives. First of all, according to sources, firecrackers can trigger pneumonia or bronchitis caused by inhaling the smoke generated by firecrackers ( Kammerer; South China Morning Post ). Furthermore, many children do not realize the danger firecrackers can cause and are often burned and injured by these substances. Even adults can be physically harmed by firecrackers if they do not pay enough attention during the usage.

Assignment: The Darby Company Manufactures and Distributors

BA561 –winter 2006 LP Case Notes: 1. This is an individual assignment. As stated in the syllabus you must do your own work or you will fail the class. 2. You can use any software you wish to perform the analysis, but the assignment was designed under the assumption that you would be using the LINDO software used for LP in BA555. 3. The project is due at the beginning of class in week four (February 1). The Case: The Darby Company manufactures and distributes meters used to measure electric power consumption. The company started with a small production plant in El Paso, Texas and gradually built a customer base throughout Texas.A distribution center (DC) was established in Ft. Worth, Texas and later as business expanded to the North, a second distribution center was established in Santa Fe, New Mexico. The El Paso plant was expanded when the company began marketing its meters in Arizona, California, Nevada and Utah. With the growth of the West Coast business, the Darby Company opened a third distribution center in Las Vegas, Nevada and just two years ago opened a second manufacturing plant in San Bernardino, California. Manufacturing costs differ between the company’s two production facilities.The cost of each meter produced at the El Paso plant is $10. 50. The San Bernardino plant is more efficient and produces meters at $10. 00 a unit. Due to the company’s rapid growth, not much attention has been paid to the efficiency of the distribution system, but Darby’s management has decided that it is time to address this issue. The costs of shipping a meter from each of the plants to each of the three distribution centers is shown in Table 1. Yearly production capacity is 30,000 units at the El Paso plant and 20,000 units at the San Bernardino plant.Note that no shipments are allowed from the San Bernardino plant to the Ft. Worth distribution center. The company serves nine customer zones from the three distribution centers. The forecast of the number of meters needed in each customer zone for the following year is given in Table 2. The Unit costs of shipping from each distribution center to each customer zone is given in Table 3. Note that some of the distribution centers can not serve certain customer zones. In the current distribution strategy demand at the Dallas, San Antonio, Wichita and Kansas City customer zones is satisfied by shipments from the Ft.Worth DC. In a similar manner the Denver, Salt Lake City and Phoenix customer zones are served by the Santa Fe DC. And the Los Angles and San Diego customer zones are satisfied by the Las Vegas DC. To determine how many units to make at each plant, the customer demand forecasts are aggregated at the distribution centers and a transportation model is used to minimize the costs of shipping from the production plants to the distribution centers. Issues the company wants you to address 1. If the company does not change its distribution strategy what will its manufacturi ng and distribution costs be for the following quarter? . Suppose the company is willing to change its distribution strategy so that customer zones could be served from any distribution center for which costs are available. Would this reduce total costs? If so by how much? Would you make this change? Please be sure to examine all supply chain implications beyond just direct dollars saved. 3. The company wants to explore the potential of direct shipping from the plants to certain customer zones. Specifically the shipping cost is $. 30 per unit from San Bernardino to Los Angeles and $. 70 from San Bernardino to San Diego.The cost for direct shipments from El Paso to San Antonio is $3. 50 per unit. Should the company do direct shipping? If so on which routes? 4. In 3 years demand is expected to have increased 30% on average across all customers. At that time the company expects to have saturated the markets they presently serve (in other words additional growth will have to come from n ew markets). It will cost 3 dollars a unit to increase capacity at the El Paso plant and 4 dollars a unit at the San Bernardino plant. How much capacity, if any, would you add to each plant to satisfy future demand?Instructions: 1. When answering the questions it is expected that you address the following: a. What is the mathematically optimal way to meet all demands and constraints at the minimal cost? You must use LP to answer this question. b. The LP model gives you the minimum cost solution. What assumptions are you making if you implement the optimal solution from the model? At a minimum pleases be sure to consider: i. Quality ii. Delivery reliability and speed iii. Managing logistics iv. Optimizing the supply chain v.Customer satisfaction 2. You must turn in a disk (floppy, cd or dvd) that contains all models you used to write the paper. The disk should contain the models and the solutions. Assignments that are not accompanied by a disk with the models and solutions will lose 30%. You can not turn your models and solutions in late. 3. You may use any software supported by the COB you wish- but Dr. Pagell will be using LINDO. 4. Your assignment will have an appendix where the models are explained, Please use typical LP nomenclature (let statements and the like).If the professor can not figure out what the variables in your models represent you will lose points. 5. You will have a second appendix with a print out of your results. If you run multiple models you will need to print out results from all of the runs. 6. When it comes to format you do what you think is best to answer the questions with the following expectations / limitations: a. You will turn in a well written, grammatically correct, logically consistent paper. b. Presentation will be professional. Everything should be typed, easy to read, laid out in a logical manner, and so on. . Make sure you tell the reader where to find information. For instance if you are using a dual price to answer a qu estion say so. And tell the reader where to find this information in the paper. I am not going to guess where information comes from. d. This is a paper not a 4 questions test. I expect you to write a paper that integrates all four questions. Papers where each question is in its own stand alone section with no linkages to other sections of the paper will get lower grades than papers that integrate the information.Grades: Your grade will be based on the proper formulation, solution and interpretation of the models. Formulation and solutions will be worth 70% of your grade and interpretation will be 30% of your grade. The instructor reserves the right to give bonus points to students who come up with very elegant formulations. Table 1 Shipping cost per unit from production facilities to distribution centers | |Ft. Worth DC |Santa Fe DC |Las Vegas DC | |El Paso Plant |$ 3. 0 |$ 2. 20 |$ 4. 20 | |San Bernardino Plant |- |$ 3. 90 |$ 1. 20 | Table 2 Yearly demand forecast |Customer Zone |Demand in meters | |Dallas |6300 | |San Antonio |4880 |Wichita |2130 | |Kansas City |1210 | |Denver |6120 | |Salt Lake City |4830 | |Phoenix |2750 | |Los Angles |8580 | |San Diego |4460 | Table 3 Shipping costs from DC’s to customer zones in dollars ($) |Customer Zone | DC |Dallas |San Antonio |Wichita |Kansas City |Denver |Salt Lake City |Phoenix |Los Angles |San Diego | |Ft. Worth |. 3 |2. 1 |3. 1 |4. 4 |6. 0 |- |- |- |- | |Santa Fe |5. 2 |5. 4 |4. 5 |6. 0 |2. 7 |4. 7 |3. 4 |3. 3 |2. 7 | |Las Vegas |- |- |- |- |5. 4 |3. 3 |2. 4 |2. 1 |2. 5 | |

Childhood Resilience and Vulnerability - Free Essay Example

Sample details Pages: 8 Words: 2447 Downloads: 7 Date added: 2019/03/13 Category Sociology Essay Level High school Tags: Childhood Essay Did you like this example? Abstract Resilience and vulnerability among children has been an ongoing topic in research of developmental psychology. These two definitions are closely tied together as they are considered both sides to the spectrum. Schaffer (2006) defines resilience and vulnerability as the susceptibility to develop malfunctioning following exposure to stressful life events, as opposed to the capacity to maintain competent functioning stress. Don’t waste time! Our writers will create an original "Childhood Resilience and Vulnerability" essay for you Create order If stressful life events are the trigger here, why is it that some children are far more vulnerable, yet others are more resilient? The three studies discussed in this paper will attempt to explain why these differences occur and what can we do to enhance protective factors. Introduction An easy way to conceptualize the term resilient is defined by Berger (2008). Berger (2008) refers to resilience as the capacity to adapt well to significant adversity and to overcome serious stress. According to Berger (2008) there are three parts to this definition: resilience is dynamic, it is a positive adaptation to stress, and adversity must be significant. In regards to Bergers first part, it is apparent that resilience is dynamic. In one article, a 14-year old girl was described as living absent from her institutionalized mother, and because of this she was responsible for taking care of her younger siblings and alcoholic father (Alvord Grados, 2005). Results of a longitudinal study concluded that although she should have formed an avoidant relationship with a future partner, she went on to form a secure and long-lasting marriage. The article questions if she was good at coping (resilient) or was she invulnerable? Second part to Bergers definition is the fact that resilience is a positive adaptation to stress. A more recent study has given us evidence that children can recover and develop normally (Alvord Grados, 2005). These findings were evident when deprived orphans from Romania were adopted to amorous families living in the United Kingdom. Following the adoption, cognitive and physical growth increased. These children had the ability to continue their growth through wise choices, enhanced education, and take advantages of new opportunities (Alvord Grados, 2005). Finally, Berger (2008) explains Adversity must be significant. Some adversities are comparatively minor (large class size, poor vision), and some are major (victimization, neglect). Looking at adversity from a humanistic perspective we need to recognize individual differences, such as culture, gender, and emotional experiences. Keep in mind, resilience is not a personality trait, it is a process. Contributing risks and factors Schaffer (2006) defines risk and protective factors as conditions that increase the probability of some undesirable outcome or, on contrary, conditions that buffer the individuals against undesirable outcomes. Risk and protective factors exist independently from one individual to another. Not only are an individuals characteristics important, but their physical, social, and family environments. According to the Centre for Addiction and Mental Health (2009), a protective factor would be considered a child living in a two-parent house. If one of the parents is in any form abusive to the other parent, or the child the living situation would be altered to a risk factor. However, not living with the abusive parent would result back into a protective factor. Therefore, factors rotate in a cycle. If protective factors are what we are aiming to improve, we must be aware of the individuals developmental stage, and also the cultural factors that come into play (Alvord Grados, 2005). Alvord and Grados (2005) have broken down protective factors into six categories. These six categories appear to be the buffers against risk factors (Alvord Grados, 2005). Many of these components are coexisting with each other. The first protective factor is proactive orientation. Proactive orientation is Taking initiatives in ones own life and believing in ones own effectiveness, this has been identified as a primary characteristic in defining resilience (Alvord Grados, 2005). Children who are high in proactive orientation develop hopefulness about the future, and view hardships as learning experiences. (Alvord Grados, 2005). Self- Regulation is another key protective factor. It is the ability to develop self-discipline or self-control (Alvord Grados, 2005). Connections and Attachment is the third protective factor. This consists of the desire to belong and to form attachments with family and friends (Alvord Grados, 2005). The need for connections and attachment is human instinct. Proactive parenting has a large impact in the production of protective factors. Children whom have at least one warm and caring parent or caregiver are more likely to be resilient (Alvord Grados, 2005). These caregivers should form limits and boundaries for the child to abide to; this improves compliance with caregiver-child relationships, along with better peer relationships (Alvord Grados, 2005). School achievements and involvement, IQ, and special talents are also an important protective factor (Alvord Grados, 2005). This gives the child a chance to excel, academically or socially. Building up a sense of self-pride and self-efficacy is good for any individual. Cognitive ability has been found to be associated with resilience in children (Alvord Grados, 2005). The last protective factor that Alvord and Grados (2005) talk about is community factors. The main question is, are there supportive relationships available outside the family? Children with positive role models and elders in their lives are often more resilient (Alvord Grados, 2005). Also, having mentors such as coaches and teachers are important, this is why after school activities are suggested (Alvord Grados, 2005). Theories derived from clinical designs There have been many research designs to make these theories empirical. Three studies will be discussed; they all examine the levels of resilience among individuals and how many unconscious surroundings have an effect on a childs vulnerability. Keep in mind that many stresses that might be daily hassles can accumulate to become major if they are ongoing (Berger, 2008, p 353). A wonderful study by Matheson et al (2005) made the quote by Berger evident. This study assessed the effects of road traffic and aircraft noise on the childrens cognitive development and health (Matheson et al, 2005). Over 2800 children were a part of the research method; ages 9-10, from eighty-nine primary schools situated close to three of the major airports in Europe. The three airports participating in the study were: Schiphol (Netherlands), Barajas (Spain), and Heathrow (United Kingdom). The question that Matheson et al (2005) were aiming to answer was, at which point are noise levels optimal for learning? The noise exposure was based on a sixteen-hour outdoor contour provided by the Civil Aviation Authority. Matheson et al (2005) measured the road noise based on the proximity from the school to the main roads, and traffic flow was based on the UK Calculation of Road Traffic Noise method. These were standardized tests. They compared the external noise to the levels of cognitive tests and health questionnaires administered in the classroom. Information about their socioeconomic status, education, and ethnic group was gathered from the childrens parents. The childrens outcome measures focused on two parts: recall and recognition. Matheson et al (2005) assessed episodic memory in terms of, delayed recognition, prospective memory, and delayed cued recall. Delayed recall and recognition were tested by the Childrens Memory Scale. The Childrens Memory Scale is an episodic memory task used in the USA and UK. The test assesses the ability to process, encode, and recall meaningful verbal material that is presented in narrative format (Matheson et al, 2005). The three countries were exposed to two stories, in audio form, taken from the Childrens Memory Scale. Matheson et al (2005) explains that the children were advised to listen carefully with understanding they would have to recall them later. There was a thirty-minute delay between the audio tape and the recalling of the story. In order for the child to receive a recall point, it had to be in the exact manner the information was presented in the tape. The other way the childrens answers were recorded was their conceptual recall of the themes, not just the details. The scoring of the conceptualized themes were much more lenient (Matheson et al, 2005). Following the recall test, a delayed recognition test was given. This test also consisted of two parts. Matheson et al (2005) explains the experimenter read out fifteen recall questions that consisted of facts. The children were instructed to check the yes or no box on a response sheet. The results of the study showed that, exposure to aircraft noise impaired reading comprehension and recognition. The average reading age in children exposed to aircraft noise in high levels was delayed by two months in the UK and one month in the Netherlands. The exposure to neither road nor air craft noise had no effect on the sustained attention, mental health, or self-reported health on the children. Long-term exposure to both the aircraft noise and road noise was associated with increased levels of annoyance. This shows that children are vulnerable to environmental factors that we impose on them every day. Some children are more resilient to these noises, whilst others are not. Thus, we need to be far more aware of the situations children are forced to learn in. If a child lives near an airport, tha t stress happens several times a day, but for just a minute at a time. (Berger, 2008, p 354). Cohen, Moffitt, Caspi, Taylor (2004) examined children that were exposed to socioeconomic deprivation. Cohen et al (2004) explains that children in low socioeconomic status families are at higher risk for both cognitive and behavioral problems. However, not all poor children develop problems, and some of these resilient children function better than expected (Cohen, Moffitt, Caspi, Taylor, 2004). The study tested for the factors that contributed to the resilience and vulnerability deprivation, such as genetic and environmental contributions. The findings that Cohen et al (2004) presented, explained that resilience is somewhat heritable. The childrens resilience had been assessed by the difference between their actual scores and the average scores predicted from the levels of their SES deprivation. Maternal warmth, stimulating activities, and childrens outgoing temperament appeared to promote positive adjustment in children exposed to SES deprivation (Cohen et al, 2004). With this knowledge, Cohen et al (2004) reveals that both genetic and environmental effects are a part of protective processes. However, Kitano and Lewis (2005) suggest that children who are more culturally diverse and come from low-income families have experience in overcoming adversity. It looks promising to say that higher intelligence or higher SES is not a requirement for resilient children. There are too many confounding variables to determine the cause of resiliency. Kitano and Lewis (2005) suggest that resilient individuals and gifted children share many of the same characteristics. This is why educating parents, counsellors, and teachers, on coping skills will benefit children both socially and academically. A study conducted by Daud, Klineberg and Rydelius (2008) was aimed towards studying the resilience among children whose parents suffer from post-traumatic stress disorder (PTSD). The test group consisted of 80 refugee children aged 9-17, 40 boys and 40 girls. The controlled group was made up of 40 children, whose parents were not diagnosed with PTSD. Intelligence tests and diagnostic interviews were set up to see if the test group children were mirroring their parents exhibited PTSD symptoms. Dauds et al (2008) questionnaires were able to assess self-esteem levels and the possibility of resilience and vulnerability characteristics. Daud et al (2008) conceptualized vulnerability as heightened susceptibility to develop PTSD or a clinical picture dominated by PTSD-related symptoms. Daud et al (2008) conceptualizes resiliency as a universal human capacity to cope with traumatic events, but that this capacity needs encouragement and support within a facilitative environment to enable resilience to win over vulnerability and risk. Parents and caregivers should be aware of Dauds et al (2008) findings. Family characteristics such as warmth, cohesions, structure, and secure attachments are all in relation to resilience among children. Promoting Resilience In order to promote resilience among children, counsellors, educators, and parents need to understand some of the protective factors. Resilience should be seen as a set of internalized attributes, Resilience involves action (Alvord Grados, 2005). Youth who are resilient are proactive when faced with challenges. They adapt to difficult circumstances by using internal and external resources. Resilient children come to understand that although they cannot control everything, they have some power to influence what happens next, explains Alvord Grados, 2005. Wouldnt it be nice if all children had the ability to make the best of everything? These studies indicate that risk and protective factors are usually cumulative: the more protective factors in young peoples lives, and the fewer risk factors, the greater the probability that these children or youth will be resilient (Center for Addictions and Mental Health, 2009). A metaphorical example to what resilience really is explained tremen dously by Centre for Addictions and Mental Health (2009): Conclusion Young people are like trees. They come in various shapes and sizes and grow up in most parts of the world. Families can be thought of as the soil and water at the base of the trees. Schools, neighborhoods, communities and society at large can be compared to the sun, rainfall, insects, birds and animals. The different characteristics of trees, qualities of soils and weather condition (such as the amount of sun and rainfall) can affect the health and growth of trees. Trees go through developmental stages as they mature from young saplings to full-grown specimens. Children also go through developmental stages on their way to adulthood, and what happens to them at various stages of development can affect their outcomes. Resilient children and youth grow, branch out and flower when systems supporting their healthy development (such as well-functioning families and environments) work together. Resilient children can be encouraged to become more resilient. And children who seem to have less resilience can be helped to develop it. In conclusion, every child has the potential to be resilient; it all depends on which factors attribute to each individuals situation. References Alvord, M., Grados, J. (2005). Enhancing Resilience in Children: A Proactive Approach. †¹Professional Psychology: Research and Practice, 36(3), 238-245. doi:10.1037/0735- †¹7028.36.3.238 Berger. S. K. (2008). The Developing Person Through The Lifespan (7th ed). New York, †¹NY: Worth. Centre for Addiction and Mental Health (2009). Retrieved March 20, 2011, †¹from https://www.camh.net/ Daud, A., Klineberg, B,. Rydelius, P. (2008). Resilience and Vulnerability among Refugee †¹Children of Traumatized and Non-traumatized parents. Child and Adolescent Psychiatry †¹and Mental Health, 13(3). doi:10.1186/1753-2000-2-7 Kim-Cohen, J., Moffitt, T. E., Caspi, A., Taylor, A. (2004). Genetic and Environmental †¹Processes in Young Childrens Resilience and Vulnerability to Socioeconomic Deprivation. †¹Child Development, 75(3), 651-668. doi:10.1111/j.1467-8624.2004.00699.x Kitano, M. K., Lewis, R. B. (2005). Resilience and Coping: Implications for Gifted †¹Children and Youth At Risk. Roeper Review, 27(4), 200-205. †¹doi:10.1080/02783190509554319 Matheson, M., Clark, C., Martin, R., Van Kempen, E., Haines, M., Barrio, I., Stansfeld, S. †¹(2010). The effects of road traffic and aircraft noise exposure on childrens episodic †¹memory: The RANCH Project. Noise Health, 12(49), 244-254. doi:10.4103/1463-†¹1741.70503 Schaffer, H.R. (2006). Key concepts in developmental psychology. Thousand Oaks, CA: Sage †¹Publications Ltd