ALU 301 Chapter 7 Exam Questions With 100% Correct Answers

ALU 301 Chapter 7 Exam Questions With 100% Correct Answers Dr. William Einthoven - answerDutch doctor and physiologist; invented the first practical electrocardiogram (EKG, ECG) in 1901. EKG - answerHas remained the most commonly used non-invasive diagnostic cardiac test worldwide. It serves as an important tool for the diagnosis of ischemia and myocardial infarction. It is the most accurate means of identifying significant arrhythmias and conduction abnormalities that carry extra mortality risk. Purpose of the cardiovascular system - answerTo meet the oxygen demands of the body and to transport waste products away from tissues for excretion. The efficiency of this system depends heavily on the ability of the heart to generate a cardiac output of approx. 5 liters of blood each minute. Requirements for heart to function effectively? - answer1. The contraction of the muscle cells must occur at regular intervals and be synchronized. 2. Ventricular contractions must be forceful. 3. The heart valves must be competent, allowing only one-directional flow of blood through the heart. 4. The ventricles must fill adequately during diastole. Myocardial cells - answerGenerate the contractile force necessary to propel blood through the circulatory system. Pacemaker cells - answerProvide the electrical stimulus necessary to initiate contraction of the myocardial cells in a coordinated manner and at appropriate intervals. Conduction system - answerComposed of pacemaker cells and is responsible for initiating and transmitting the electrical impulse required in order to stimulate contraction of the myocardial cells. Sinoatrial (SA) node or sinus node - answerLocated in the superior and posterior wall of the right atrium. It spontaneously initiates each electrical impulse and governs the physiologic heart rate. Atrioventricular (AV) node - answerLocated at the AV junction along with the bundle of His. As the impulse reaches the AV node, its transmission to the bundle of His is delayed. This allows the mitral and tricuspid valves to open, the ventricular walls to relax and the atria to contract. The bundle of His - answerLocated in the septum and divides into the right bundle branch and the left bundle branch. The left bundle branch divides again into the left anterior and posterior fascicles. These divisions allow the impulse to be rapidly transmitted throughout the ventricles. The Purkinje fibers - answerA network of conducting strands that lie beneath the ventricular endocardium. They are responsible for the conduction of impulses to the myocardial cells. Action potential - answerThe voltage changes that occur across the cell membranes during the cardiac cycle as a result of electrolyte exchanges. Depolarization - answerRepresents the electrical activation of myocardial cells due to the spread of an electrical impulse. Contraction - answerThe mechanical event that occurs after depolarization has taken place. Repolarizaton - answerThe process by which the cells return to their resting state. What does an EKG provide? - answerRecord of how the voltage between two points on the body surface changes with time as a result of the electrical events of the cardiac cycle. (depolarization and repolarization) Limb leads - answerBipolar leads and unipolar leads. Bipolar leads utilize one positive and one negative electrode and include leads I, II and III. Unipolar leads use just one positive electrode. Also augmented leads - aVR, aVL and aVF. Precordial (chest) leads - answerUnipolar leads and lie in a horizontal plane perpendicular to both the chest and to the frontal plane of the limb leads. The precordial leads consist of V1 through V6 with lead placement across the chest. P wave - answerP wave represents atrial depolarization; a normal P wave is gently rounded; its height is normally less than 3mm and its width less than 0.11 seconds. P wave can be biphasic, meaning falling both above and below the baseline, in leads III, aVL and V1 through V3. PR Interval - answerMeasured from the beginning of the P wave to the beginning of the QRS complex. It represents the time required for depolarization of the atria to the onset of depolarization of the ventricles. A normal PR interval ranges from 0.12 to 0.20 second. QRS complex - answerRepresents ventricular depolarization. Q wave - answerThe initial downward (negative) deflection in the QRS complex. There can be small, insignificant Q waves in a normal EKG.