Work Of The Heart (1967)

number of in a lifetime about 4 billion amount of blood pumped in a lifetime more than 540,000 metric tons nature of work to pump blood continually to and from the 50 trillion cells in the human body blood the coursing life stream of body blood continually transporting oxygen and nutrients to every cell and absorbing carbon dioxide and other wastes blood the unique fluid that is essential to the life processes of the cells the means by which this vital fluid streams through the body is a system of vessels the human blood transport system system is a complex of branching vessels vessels that carry the blood to the cells and vessels that carry it away from the cells maintaining the flow of blood through this transport system is the work of the heart the pump of life this powerful organ is extremely sensitive to changing needs of the cells for blood during active exercise the body cells produce large amounts of wastes and require increased amounts of oxygen and nutrients when the body is at rest the cells produce smaller amounts of waste and require less oxygen and nutrients the heart adjusts to these varying demands mainly by pumping at slower or faster rates this heart that of an anesthetized dog will be used to demonstrate how the rate of beat is affected by various body mechanisms these sounds were recorded by placing a microphone on the exposed heart electric probes simulate the effect of nerve impulses on rate of beat stimulating a nerve called the Vegas has this effect when another nerve one of the sympathetic nerves is stimulated this effect is produced the rate of beat is also affected by another mechanism chemicals called hormones produced by the endocrine glands and released directly into the bloodstream the dark solution in the syring contains a small quantity of the hormone epinephrine normally produced in the adrenal glands after injection into the bloodstream several seconds will pass before its effect on the raid de beat can be seen the solution in this syringe contains acetylcholine a chemical normally found in nerve cells whatever the rate at which the heart beats the pattern of each bead is essentially the same when photographed in slow motion this pattern becomes more clear the beat starts here and then spreads across the rest of the organ like a wave there are two definite parts to the wave first a contraction scientific name cyy syy is followed by the second part of the wave a relaxation scientific name diesto CYO and diast follow each other in a rhythmic pattern this wavelike beat of the heart has been an area of intense research in one demonstration a culture of cells taken from the heart of a rat embrio is prepared the cells are kept alive in a nutrient solution individual heart cells show independent rates of beat early in life if the cells continued to beat independently the heart could not contract and relax as a unit after a short time however a network of fibral forms connecting the cells across this network those few cells which beat fastest transmit their rate to the other cells so that all heart cells beat uniformly even an embryonic heart like this that of a chick embryo less than 2 days old beats rhythmically and as a unit long before nerve connections have been established to it the heart's tendency to contract act and relax is so strong that as in this specially prepared turtle's heart it will continue to beat independently even after it has been removed from the body in mamalian Hearts human included the beat originates with a group of specialized cells located here this region is named the pacemaker the cells of the pacemaker beat fastest and set the rate of beat for the entire organ the heartbeat is electrochemical in nature and can be measured with an instrument called the electrocardiograph this instrument amplifies very small electrical potentials which are conducted through electrodes the electrical potentials are traced out by a moving dot on an oscilloscope screen dipping the electrodes in tap water in which the electrical potentials are extremely small demonstrates the delicate sensitivity of the electrocardiograph the writer of heart electricity though not standard procedure the electrodes may be placed directly on the heart a tracing called an electrocardiogram or ECG is recorded the ECG is a graphic record of the heart's electrical activity as it rhythmically contracts and relaxes to understand the work of the heart as it beats some idea of its interior structure is needed this is a schematic view of the organ as it is positioned in the body the heart is made up of four compartments or Chambers The upper chambers Atria receive blood from the body the lower Chambers ventricles eject blood into the body one-way valves separate Atria and ventricles a wall divides the four chambers into a double pump this ventricle n Atrium form the left pump this ventricle and Atrium the right pump the course of blood through the right pump when the atrium relaxes oxygen pour blood from the body flows from large veins into it the blood continues past this valve called the tricuspid and begins to fill the right ventricle with contraction blood in The ventricle is pushed back against the valve flaps these flaps Under Pressure snap shut sealing off The ventricle from The Atrium using a specially prepared heart the true action of the various valves can be observed here's the action of the tricuspid valve as the Heart Is Made to contract and relax note how the valve snap shut under the pressure of the backward flow of fluid with contraction blood trapped in the right ventricle is squeezed past another one-way valve the pulmonary into the pulmonary artery which leads to the lungs this valve opens during contraction closes during relaxation as blood in the pulmonary artery flows back against the flaps watch the complete right pump cycle again this time at a more normal speed through this action the right atrium and ventricle act to pump oxygen pour blood to the lungs blood from the lungs enters the left side of the heart by flowing from the pulmonary vein into the left atrium fresh supplies of oxygen give this Blood its bright red color flowing past this valve the mitol blood fills the left ventricle contraction begins the valve closes as blood in The ventricle is pushed back against it action of the mitol in the specially prepared heart and here a rarely photographed view of the mital valve in a living heart as the left ventricle continues to contract blood trapped in it is forced past another one-way valve and ejected into the aorta this large blood vessel branches to carry oxygen-rich blood to every part of the body to sum up the action of the left pump sends oxygen rich blood to the body the action of the right pump sends oxygen poor blood to the lungs both pumps function together as a single unit the pumping of the heart is accompanied by two distinct sounds one when this pair of valves closes one when the this pair closes the heart's pumping efficiency is directly related to how well its valves [Music] function for this reason listening to the heart with an instrument called the stethoscope is basic to any routine physical examination occasionally The Physician may hear a sound pattern that is not normal like this a heart murmur among the most common of heart diseases murmurs are due to valves that do not close properly usually this condition is not dangerous sometimes however as is the case with this mital valve the valve is so inefficient it must be replaced with an artificial valve this is one type of artificial valve designed to be placed within the human heart the ball moves back and forth in response to the flow of blood in recent years valve replacement has become a relatively routine safe operation because the beating of the heart is stopped during surgery the aorta and major veins leading to the organ must be connected to a heart lung machine its major function is to take over temporarily the work of the heart and lungs in delivering oxygenated blood to the body now the heart may be open the diseased valve is exposed and remove the artificial valve is prepared for placement inside the heart carefully it is sewn into place with the valve holder removed the efficiency of the device is checked the operation completed the heart is electrically stimulated into resuming its beat modern heart surgery including valve replacement is the result of relatively Recent research directed toward lengthening the human lifespan further refinements and Innovations in cardiac repair perhaps leading to replacement of the pump of life itself is a major goal of continuing Research into the work of the heart