BIO 241 1nd Edition Lecture 5 Outline of Last Lecture I. Rh system II. Introduction to the heartIII. PericardiumIV. Heart wallV. Heart chambersVI. Septa of the heartVII. Blood flow through the heartVIII. Atrioventricular ValvesIX. Semilunar ValvesOutline of Current Lecture II. Coronary circulation – the arteriesIII. Coronary circulation – the veinsIV. Conduction system and pacemakersV. Conduction system componentsVI. Timing of conduction eventsVII. Electrocardiogram (ECG or EKG)Current LectureII. There is a left coronary artery that branches to make both the anterior interventricular artery/left anterior descending artery and the circumflex artery. There is a right coronary artery that branches to form the posterior interventricular artery and the marginal artery. Do not remember the ones that are not mentioned above. Anastomoses is known as the connection of blood vessels and contributes to the collateral circulation which refers to the flow of blood.III. The veins consist of the great cardiac vein, the middle cardiac vein, and the small cardiac vein. Thecoronary sinus ultimately receives all cardiac venous blood and returns it to the right atrium. These are shown below:IV. The heart stimulates itself with autorhythmic cells. Autonomic nervous system and hormones can only modify, but not establish, the fundamental rhythm of the heart. All cardiac muscle cells are autorhythmic, but 1% lose the ability to contract during early development. Those cells that cannot contract form the pacemakers (primary and secondary) and the conduction system.V. There are two different nodes within the heart. The first is the sinoatrial (SA) node and is the primary pacemaker. It has an action potential of 90-100 beats per minute. This node comes from internodal fibers. The secondary pacemaker is the atrioventricular (AV) node and is embedded in the cardiac skeleton. It has an action potential of 40-50 beats per minute. A heart can contract randomly and that is called fibrulation. VI. The cardiac muscle first contracts at the septum toward the apex like ringing out a dish rag. The AV node acts like a physiological block, causing a delay in conduction through the cardiac skeleton. The diagram will help understand where conduction travels. You do not need to remember specific times just the route it travels. VII. Electrocardiograms are measurements of electricity passing through the heart during a cardiac cycle. Electrodes are placed on both wrists and ankle. Our bodies are mostly water and water is a good conductor of electricity. There is a P wave which is atrial depolarization. The QRScomplex contraction is ventricular depolarization. Lastly, a T wave occurs. It is ventricularrepolarization. Things that depolarize usually have to repolarize. Notice there is no wave for atrial repolarization. That is because the QRS complex hides the event. The point from the vertex of the T wave to the beginning of the P wave is called the quiescent
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