Cardiac Rhythms & Dysrhythmias from health stream (solved & updated ).

Sinoatrial (SA) node the pacemaker; highly specialized, neurological tissue impeded in the wall of the right atrium; responsible for initiating electrical conduction of the heartbeat, causing the atria to contract and firing conduction of impulses to the AV node A cluster of specialized myocardial cells located high in the right atrium and adjacent to the superior vena cava AV node (atrioventricular node) The AV node is located in the interatrial septum close to the tricuspid valve. The AV node has an intrinsic rate of 40 to 60 beats per minute. The impulse is momentarily delayed in the AV node, allowing the atrium to contract and fill the ventricles Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0:00 / 0:15 Full screen Brainpower Read More Bundle of his The impulse then enters the ventricular conduction system through the AV node. The ventricular conduction system is made up of the bundle of His and the left and right bundle branches. The bundle of His has an intrinsic rate of 20 to 40 beats per minute. Purkinje fiber From the bundle branches, the impulse is carried to the ventricular muscle by the network of specialized Purkinje fibers. Sinus bradycardia is considered physiologic (normal) when found in young adults or athletes. Alert In a patient with ischemic heart disease, sinus bradycardia can be a warning that an SA block or SA arrest is impending. Bradycardia can occur during sleep in response to a slowing metabolism. What are some other causes of bradycardia? Causes of sinus bradycardia can include: Hypothyroidism Increased pressure in brain due to hemorrhage Myocardial infarction (MI) Impending SA block Hyperkalemia Drug toxicity What is the significance of, and proper treatment for, sinus arrhythmia? normal variant - no treatment required unless the patient is symptomatic. Sinus arrhythmia also originates from the SA node. However, the rhythm is irregular and commonly associated with respiratory patterns, increasing with inspiration and slowing with respiration. AV node Cluster of cardiac cells between the atria and ventricles that can serve as the pacemaker of the heart Though the sinoatrial (SA) node is the normal pacemaker of the heart, the atrioventricular (AV) node can also pace the heart's conduction system. The area of the AV node is called the junction. This is where the conduction pathway passes from the atria to the ventricles. This junction, also known as the nodal area, contains cells with pacemaking properties. The purpose of the junctional cells in the AV nodal region is to provide the heart's conduction system with a backup, in the case that the SA node is depressed or fails to initiate electrical impulses appropriately. Irritable focus A locus of cardiac cells that depolarize prematurely, initiating an electrical impulse that causes early depolarization and contraction of cardiac muscle When an irritable focus in the junctional tissue initiates an impulse early, it produces a single ectopic impulse called a premature junctional