The functioning of the conduction system of the heart Show The components of the cardiac conduction system include (in correct sequence) the sinoatrial (SA) node, the atrioventricular (AV) node, the atrioventricular (AV) bundle, the atrioventricular (AV) bundle branches, and the Purkinje fibers. Cardiac pacemaker cells that form this system do not have a stable resting membrane potential like skeletal muscles or neurons.
The signal from the pacemaker cells is then transmitted to contractile myocardial cells as these cells are stimulated to generate an action potential.
All components of the conduction system of the heart function similarly. However, each individual component has certain unique characteristics. For example, the SA node is considered the pacemaker of the heart because it initiates the heart rhythm known as the sinus rhythm, while the Purkinje fibers have the fastest speed of signal conduction. You can watch Conducting the Signal to see a visual for the conduction of the electric signal. The Electrocardiogram (ECG or EKG) The ECG is made up of a straight baseline and waves. The waves can either
move over or under the baseline.
Which of the following is a recording of all nodal and myocardial?An ECG is a composite recording of ALL action potentials produced by the nodal and myocardial cells—it should not be construed as a tracing of a single action potential.
What is a composite recording of all cardiac action potentials?Electrical activities of the heart can be recorded in the form of electrocardiogram, ECG or EKG. An ECG is a composite recording of all the action potentials produced by the nodes and the cells of the myocardium. Each wave or segment of the ECG corresponds to a certain event of the cardiac electrical cycle.
Which structure initiates the action potential in the heart?The cardiac action potential originates from the sinus node, located high in the right atrium (Fig. 9-1). Its cells depolarize spontaneously and initiate the spontaneous depolarization of action potentials at a regular rate from the sinus node.
Which electrocardiogram ECG finding can be used to measure heart rate?For regular heart rhythms, heart rate can easily be estimated using the large squares (0.2s) on an ECG. Simply identify two consecutive R waves and count the number of large squares between them. By dividing this number into 300 (remember, this number represents 1 minute) we are able to calculate a person's heart rate.
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