Sunday, March 31, 2019

Physics of the Heart

Physics of the HeartElectrocardiographyElectrocardiography is the arrangement of the galvanizing of the flavor by a non-invasive procedure. This is possible beca commit the personate is an electric conductor, the ECG work acts as a voltmeter and voltage duration characteristics be mea currentd by attaching electrodes to the endurings skin.Electrical itchs created by the conducting weave of the tenderness and soul are picked up. The Sino Atrial Node (a small area of heart that triggers muscle muscular contraction, acting as a pacemaker) is located at the happen of the proficient atrium and sends a jounce of electrical activity down the right atrium. Another jolt of electrical activity is sent by the auriculoventricular boss down the Bundle of His once the electrical activity by the SAN is received. There is a small delay before the AVN sends a wave of electrical activity, this is to allow the atria to empty fully before the ventricles contract.The ECG machine detect s and amplifies electrical impulses (waves of depolarisation) initiated by the SAN. Each of the heart muscle cellular ph unitys in the body generate a negative charge (at rest) this is called the membrane potential. The muscle cells have a negative charge because an active transport mechanism in the cell membrane maintains an excess of cations on the outside, and an excess of anions inside. This means there is a potential difference across the membrane. In the heart it is typically about 70 mV for atrial cells and 90 mV for ventricular cells. Decreasing the negative charge towards zero, via the flooding of cations (Na+ and Ca2+) into the cell, is called depolarisation which ultimately causes the cell to contract.A sound heart will have a typical wave of depolarisation that is initiated by the SAN, spreads out through the atria, reaches the atrioventricular node and spreads all over the ventricles. The potential difference due to the hearts electrical activity is measu chromatic by cardinal electrodes (one positive and one negative). If the electrical impulse travels towards the positive electrode the result is a positive deflection. If the impulse travels way from the positive electrode the result is a negative deflection.Electrodes are typically placed on the arms, leftover leg and one or to a greater extent over the heart. This religious services to minimise signals from other muscle cells in the body. This foundation dish up a cardiologist to understand what is happening in different split of the heart.The electrical impulses are translated into a waveform. The resulting ECG trace has a characteristic shape with sections that are labelled P, Q, R, S and T. Abnormalities in the shape of the wave are used to identify heart problems such as instant contractions of the heart. The heart has a zero potential difference across it, the contraction of the atria produces a P wave (The PQ interval represents the delay to allow the ventricles to fill). The contraction of the ventricles then produces the QRS complex. Finally the T wave shows the relaxation of the ventricles. The period (R-R interval) is the time between adjacent peaks in the ECG trace. In a healthy person this varies by up to 10% between each heart beat. Heart rate is determined by averaging over multiple heart beats (Heart rate = 1/average period). The heart rate in beats per minute is equal to the frequency in hertz (Hz) x 60.The Physics of the Artificial HeartIn artificial hearts (such as the one made by AbioCor), the electronic kit is implanted in the abdomen of the person receiving the transplant to monitor and regulate the pumping of the artificial electronic heart.Power is supplied from an external battery pack to components inside the patient, without penetrating the skin, using inductive electromagnetic coupling. A principal similar to this is used by transformers in the national grid. The internal battery can provide up to 40 minutes of power when disconnect ed from the external battery pack, for when the patient may want to have a shower for example.In transformers, an electrical current passes through a wire wound rough a core, called the primary lock. Another wire is wound around the same core, this is called the vicarious coil. If the two coils have the same number of turns around the core, it allows the primary coil to pass an exact copy of its electrical current to the secondary coil. These types of transformers are normally called isolation transformers. This allow two circuits to be electrically coupled, without the two circuits actually coming into direct physical contact. The image on the left shows a typical isolation transformer but the one used in this case is considerably smaller in size.The patient is constantly mournful so it is quite difficult to keep the two coils aligned. This is important because the go down level of energy inescapably to be rapture wild via the wireless energy transfer system so that there is no excess transferred as soup up to the surrounding tissue of the patients body this could cause expert damage. Also the components need to be small enough to be carried around without too much discomfort.Furthermore, the artificial heart needs to be suitable to monitor the flow of blood to maintain its pumping action and make sure the correct amount of blood is being pumped. The rate of the pumping of the blood needs to be altered when the patient requires more or less oxygen, for example more oxygen is required during higher rates of respiration. Blood-flow monitors make use of ultrasound ultrasound is used because the flow of blood can be monitored without having to be in contact with it. High-frequency sound waves are reflected off red blood cells coming out of the heart. The volume and speed of the blood can be measured using similar principles to those behind radar. The movement of these red blood cells, either towards or away from the transmitted waves, results in a frequ ency shift (due to the Doppler Effect) that can be measured. This data can help the system to determine the speed and direction of blood flow in the heart.Bibliographyhttp// document/heart/http// Parker (2009).The Concise Human proboscis Book. London Dorling Kindersley Limited. p154-155.Adam Hart-Davis (Editor-in-Chief) (2009).Science, The Defini tive Visual Guide. London Dorling Kindersley Limited. p406-407, p448.Word conceive (excluding Bibliography and Headings) 991

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