Chapter 19- Cardiovascular System: Heart.... Anatomic Structures Controlling Heart Activity

Autorhythmicity (???)

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Intro (not on word list and do not need to know but helpful)

*The heart pumps blood continuously and depends upon rhythmic stimulation of cardiac muscle cells. Precise electrical events are orchestrated by the heart's conduction system, beginning with stimulation by the sinoatrial node and then transmission of an action potential by specialized conduction fibers of the heart to ensure that the atria are stimulated to contract prior to the ventricles.* These events are influenced by the activity of the autonomic nervous system.

Figure 19.14 (Anatomic Structures Controlling Heart Activity) explained...

The heart's conduction system, composed of the Sinoatrial (SA) node, Atrioventricular (AV) node, right and left bundles, and Purkinje fibers, , initiates and conducts the electrical activity to cause heart contraction. *Heart rate and force of contraction are modified by autonomic centers (cardioacceleratory and cardioinhibitory centers) in the medulla oblongata.* *Parasympathetic axons extend from the cardioinhibitory center to both the SA node and AV node.* *Sympoathetic axons extend from the cardioacceleratory center to the SA node, AV node, myocaridum, and coronary vessels. *

The heart's conduction system (don't need to know and not on word list but helpful)

Specialized cardiac muscle cells are found within the heart located internal to the endocardium; they're collectively called the heart's conduction system. These distinct cardiac cells don't contract, but rather they initiate and conduct electrical signals. **The conduction system includes the following structures: the Sinoatrial (SA) node, the Atrioventricular (AV) node, the Atrioventricular bundle (bundle of His), and the Purkinje fibers.**

Atrioventricular (AV) Bundle/ (Bundle of His)

The ATRIOVENTRICULAR (AV) BUNDLE/(Bundle of His) extends from the AV Node into and through the interventricular septum. *It divides into left and right bundles.*

Atrioventricular (AV) Node

The ATRIOVENTRICULAR NODE/(AV) Node is located in the floor of the right atrium between the right valve and the opening for the coronary sinus.

Purkinje Fibers

The PURKINJE FIBERS extend from the left and right bundles beginning at the apex of the heart and then continue through the walls of the ventricles.

Sinoatiral Node (SA)

The SINATRIAL NODE is located in the posterior wall of the right atrium, adjacent to the entrance of the superior vena cava. *The cells here initiate the heartbeat and are commonly referred to as the "Pacemaker" of the heart.*