Wk11 iWorx Circulation Lab(2) - iWorx Circulation Lab: The...

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iWorx Circulation Lab: The Heart, ECG, Pulse, and Heart SoundsThe heart is a pump that pushes blood around the body. Blood enters the heart at a low pressure andleaves at a higher pressure, and this high pressure provides the force to propel the blood through thecirculatory system. The organization of the human heart and the circulatory system is shown in Figure 1.Blood returning from the body is sent to the right side of the heart and then to the lungs to pick upoxygen and release carbon dioxide. This oxygenated blood is sent to the left side of the heart and back tothe body, where oxygen is released and carbon dioxide is collected. The complete division ofthe heart insures that there is no mixing of deoxygenated blood (in the right side) with oxygenated blood(in the left side).The mammalian heart is autorhythmic, since it will continue to beat if removed from the body (and keptin an appropriate solution). Heart contractions are, therefore, not dependent upon the brain, rather therhythm comes from within the heart itself. The heart is composed almost entirely of large, strong musclefibers (myocardium), which are responsible for the pumping action of the heart. Other cardiac musclecells are weakly contractile and produce or conduct the rhythm for the rest of the heart. A group ofthese weak muscle cells is located in the sinoatrial (SA) node and acts as the pacemaker for the heart(Figure 2). These cells rhythmically produce action potentials, which spread via gap junctions to fibers ofboth atria. The resulting contraction pushes blood into the ventricles. While adjacent atrial fibers areconnected by gap junctions, the only electrical connection between the atria and theventricles is via the atrioventricular (AV) node. The action potential spreads slowly through the AVnode and then rapidly through the Bundle of His and Purkinje fibers to excite both ventricles.Figure 1: A diagram to show the circulation of blood around the human body and itsassociationwith the heart, composed of a right atrium (RA), a left atrium (LA), a right ventricle (RV), and a leftventricle (LV).Amended from iWorx Experiment HH-1: The Electrocardiogram and Peripheral CirculationPage1
Figure 2: A diagram of the human heart to show the location of the sinoatrial (SA)and atrioventricular (AV) nodes.The semilunar valves are located between the ventricle and the main artery on each side of the heart. Inthe relaxed heart, the high arterial pressure shuts the semilunar valves and prevents blood flow from theartery back into the ventricle. Ventricular contraction increases the pressure of the blood in theventricle. When the ventricular pressure is greater than the arterial pressure, the semilunar valves openand blood flows into the artery. Then, the myocardium relaxes, the ventricular pressure declines, and thesemilunar valves close.

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Term
Fall
Professor
ZHAO
Tags
Chemistry, heart rate, pulse, Pulse Integral, iWorx Experiment HH 1, Pulse Transducer

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