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Understanding EKGs-4
Based on the book by Beasley, 2nd Edition
| Question | Answer |
|---|---|
| What is responsible for the electrical activity that controls each normal heartbeat? | The heart's pacing or conduction system |
| What is the unique system in the heart which consists of specialized cells & fibers? | nodes or bundles |
| What is small and is located beneath the endocardium (innermost lining of the heart chambers)? | nodes or bundles |
| What is essential to learning and understanding an EKG strip? | A thorough understanding of the electrical conduction system of the heart |
| What is responsible for electrical activity that controls each normal heartbeat? | The hearts pacing (conduction) system |
| What are the 3 internodal atrial pathways? | 1. Anterior 2. Posterior 3. Middle |
| What is the firing rate of the SA Node? | 60 - 100 beats per minute |
| What are internodal pathways? | Internodal pathways transfer impulses from the SA node throughout the atria to the AV junction |
| What is the function of the AV junction, AV node, and Bundle? | Slows impulse intrinsic firing rate of 40 - 60 beats per minute |
| What is the function of the bundle branches? | Two main branches (left & right) transmit impulse to ventricles |
| What is the function of the Purkinje network? | 1. Spreads impulse throughout the ventricles 2. Intrinsic firing rate of 20 - 40 beats per minute (bpm) |
| True or False: A clinician can determine the mechanical activity of a patient's heart by looking at an EKG strip. | False. A clinician CANNOT determine the mechanical activity of a patient's heart by looking at an EKG strip. |
| How can a clinician determine whether an EKG strip is "abnormal"? | The student must first understand the normal parameters for the graphic representation of the electrical activity of the heart. |
| What is the SA node? | The SA (Sinoatrial) node is the primary pacemaker of the heart, located in the upper posterior portion of the right atrial wall of the heart - near the superior vena cava. |
| What is the main function of the SA node? | The SA node is the primary pacemaker of the heart because it normally depolarizes more rapidly than any other part of the conduction system. |
| What does the SA node consist of? | The SA node is a cluster of hundreds of cells: a KNOT of modified heart muscle. |
| Specifically, what does the SA node or cluster of cells do? | This cluster generates impulses that travel throughout the muscle fibers of both atria, resulting in depolarization. |
| Where does the SA node receive its blood supply from? | SA artery |
| What is the SA artery? | A branch of the right coronary artery in about 60% - 70% of the population. |
| Where does the remainder of the population receive their blood supply? | 30% - 40% of the population receives their blood supply from the circumflex artery |
| What happens if the SA node is damaged? | Another group of specialized tissues (such as the atrioventricular tissue or Purkinje network of fibers) will assume the duties of the pacemaker. |
| How do these pacemakers work? | From top to bottom. In other words, from the SA node to the AV node to the Purkinje fibers. |
| What happens to the impulse after leaving the SA node and travels down the path of electrical conduction system? | Depolarization and resultant myocardial contraction occur. |
| What is a group of interatrial fibers contained in the left atrium? | Bachmann's bundle |
| What is the subdivision of the anterior internodal tract? | Bachmann's bundle |
| What conducts electrical activity from the SA node to the left atrium? | Bachmann's bundle |
| What is located on the floor of the right atrium near the opening of the coronary sinus, just above the tricuspid valve? | AV (Atrioventricular) node |
| Where is the electrical activity which is delayed by about .05 seconds? | At the level of the AV node |
| Why is electrical activity delay at the level of the AV node? | This delay allows for atrial contraction and a more complete filling of the ventricles. |
| What 3 regions does the AV node include? | 1. AV junctional tissue between the atria and node 2. Nodal area 3. AV junctional tissue between the node and the bundle of HIS |
| In the normal heart, where is the ONLY pathway for conduction of atrial electrical impulses to the ventricles? | AV node |
| The region where the AV node joins the bundle of HIS is called? | AV junction |
| What is similar to the SA node and contains fibers that can depolarize spontaneously, forming an electrical impulse that can spread to the heart chambers? | AV junction |
| What is the conduction pathway (aka AV bundle or commond bundle) that leads out of the AV node and is also traditionally referred to as the common bundle? | Bundle of His |
| What is the posterior fascicle? | Spreads impulses to the posterior ventricle wall. |
| How large is the Bundle of His and where is it? | The Bundle of His is about 15 millimeters long and lies at the top of the interventricular septum. |
| What is the interventricular septum? | The wall between the right and left ventricles. |
| What does the Bundle of His capable of? | This bundle of specialized cells contains pacemaker cells that have the ability to self-initiate electrical activity at an intrinsic firing rate of 40 - 60 beats per minute. |
| The Bundle of His is divided into two main branches at the top of the interventricular septum. What are these branches called? | 1. Right bundle branch 2. Left bundle branch :) |
| What is the primary function of the bundle branches? | To conduct electrical activity from the Bundle of His down to the Purkinje network. |
| Describe the right bundle branch. (Hint: 3 items) | 1. Long, thin structure lying beneath the endocardium 2. Runs down the right side of the interventricular septum 3. Terminates at the papillary muscles in the right ventricle. |
| What is the primary function of the right bundle branch? | To carry electrical impulses to the right ventricle. |
| Which bundle branch is shorter? | Left bundle branch |
| Describe the left bundle branch. | The left bundle branch divides into pathways that spread from the left side of the interventricular septum and through the left ventricule. |
| What are the two main divisions of the left bundle branch? | Fascicles |
| What carries electrical impulses to the anterior wall of the left septum? | Anterior fascicle |
| The bundle branches continue to divide until they finally terminate in the _________ __________. | Purkinje fibers |
| What bundle branches lead to a network of small conduction fibers that spread throughout the ventricles? | Purkinje's network |
| What network of fibers carries electrical impulses directly to ventricular muscle cells? | Purkinje's network |
| Where to the fibers that connect with Purkinje's fibers start? | In the atrioventricular node in the right atrium of the heart. |
| How can the Purkinje's network be identified? | ONLY through a microscope |
| Which fibers are larger in diameter, ordinary cardiac muscle fibers or Purkinje's network? | Purkinje's network |
| What is facilitated by the rapid spread of the electrical impulse through the left and right bundle branches and Purkinje fibers into the ventricular musle? | Ventricular contraction |
| What is the firing rate of the Purkinje pacemaker fibers? | Normally range from 20 - 40 beats per minute. |
Created by:
LoreFD
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