6.2_Healthy_hearts - Our next organ system that we will...

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Unformatted text preview: Our next organ system that we will examine is the cardio-vascular system- our heart and circulatory systems. 1 A major theme of the presentation is relating our understanding of the cardio- vascular system to effects of diet and lifestyle. Cardio-vascular disease is the leading cause of illness and death in our society and the choices we make, even early in life, can have significant consequences later. Our approach in this presentation is to overview the human cardiovascular system, investigate the process of atherosclerosis (i.e., hardening of the arteries), and examine the latest findings on how to reduce the risk of cardiovascular disease. Finally, Id like to share some of my findings from the study of essential fatty acids in the context world food supplies. 2 3 Mammals and birds have a double circulatory system where a four chambered heart pumps blood through a pulmonary circuit through the lungs and a systemic circuit through the rest of the body. This figure shows the blood flow through the double circulation of the human cardiovascular system. As a side note, the next time you find yourself doing a handstand, realize that the blood rushing to your head is not directly coming from your legs. 4 A four-chambered heart provides for an efficient delivery of blood to the two circuits- pulmonary and systemic. This Internet address takes you to a YouTube video that animates the process of blood flow through the heart: http://www.youtube.com/watch?v=rguztY8aqpk&feature=related 5 The cardiac cycle in a human provides a specific sequence of heart muscle contractions to deliver blood to the two circuits. Different stages of this cycle are named diastole and systole. During diastole, blood flows from the veins into the atria and then ventricles. During systole, the atria and ventricles contract in sequence. This creates the blood flow that is detectable as a pulse. By the way, when blood pressure is measured, the first value given is the elevated pressure produced by the ventricular contraction at the end of the systole; whereas the lowest pressure level occurring at the end of diastole is given as the second value. Therefore a typical blood pressure reading of 110 over 60 would correspond to the systole and diastole stages respectively. The next slide shows how these heart contractions are coordinated. 6 The regular beating of the heart is, to a degree, independent of the central nervous system in that the triggering of the muscle contractions is centered in a patch of tissue associated with the right atrium called the sinoatrial (SA) node. This electrical pulse excites the atrial muscles to contract and push blood into the ventricles. The electrical signal is picked up, after a short pause, at another patch of tissue called the atrioventricular (AV) node. The electrical impulse is relayed to the lower tip of the heart and then muscle contraction is propagated up the heart to push blood out of the ventricles. The sequence of electrical events in a heartbeat can be detected by using ventricles....
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6.2_Healthy_hearts - Our next organ system that we will...

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