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A&P Ex. 45

Exercise 45 : Cardiac Cycle

What constitutes a cardiac cycle? A set of atrial contractions while the ventricular walls relax, followed by ventricular contractions while the atrial walls relax
What accompanies a cardiac cycle? Accompanied by blood pressure changes within the heart chambers, movement of blood in and out of chambers, and opening and closing of heart valves
What happens when valves close? Produce vibrations in the tissues and thus create the sounds associated with the heartbeat
What creates a murmur? A turbulence due to the back flow of blood when a heart valve is closed
What does the regulation and coordination of the cardiac cycle involve? The cardiac conduction system
Where does the pathway of electrical signals originate from? Sinoatrial (SA) node located in the right atrium near the entrance of the superior vena cava
Why is the SA node also called the pacemaker? Because the stimulation of the heartbeat and heart rate originate form the SA node
As signals pass through the atrial walls toward the atrioventricular (AV) node, contractions of the atria followed by relaxations take place. Once AV node has been signaled, what happens? The rapid continuation of the electrical signals occurs through the AV bundle and the right and left bundle branches within the interventricular septum and terminates via the Purkinje fibers through ventricular walls
The completion of one cardiac cycle happens when? Once the myocardium of the ventricles has been stimulated, ventricular contractions followed by relaxations occur
What influences the activity of the pacemaker under various conditions? The sympathetic and parasympathetic subdivisions of the autonomic nervous system.
An increased rate results from __(1)__l a decreased rate results fro __(2)__ 1. sympathetic responses; 2. parasympathetic responses
Electrical changes in myocardium as it contracts and relaxes can be detected by what? Using metal electrodes and an instrument called an electrocardiograph (ECG ; EKG)
What are the electrical events of the cardiac cycle that can be observed and interpreted from the ECG graphic recording? Depolarization and repolarization
The first sound of heartbeat (lubb) happens when? When the AV valves are closing, which occurs during ventricular systole (contraction)
The second sound of heartbeat (dupp) happens when? When the semilunar valves are closing, which occurs during the ventricular diastole (relaxation).
What is a single heartbeat? It is a sequence of precisely timed contractions and relaxations of the 4 heart chambers initiated form the cardiac conduction system.
The basic rhythm of one's heartbeat is controlled by what? SA node (pacemaker), but it can be modified by the autonomic nervous system.
Created by: elizabethcosio
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