![]() Arising from these centers are two sets of nerves (figure 10.17): (1) the phrenic nerves, arising from the cervical plexus and leading to the diaphragm, and (2) the intercostal nerves, which innervate the intercostal muscles. The respiratory center is a group of cell bodies located on each side of the medulla oblongata. The result is atrial contraction rapidly followed by ventricular contraction. The impulse continues through the bundle of His (atrioventricular bundle), which divides into left and right branches (becoming known as myofibers of conduction, or Purkinje fibers) that enter the muscular walls (myocardium) of the ventricles and the papillary muscles. Specialized tissue (myocardial cells) of the atrioventricular bundle (AV node located in the lower aspect of the interatrial septum) receives the impulse after it has passed through the atrium (figure 10.16). When stimulated, the sinoatrial node (SA node) of the heart, found in the area of the right atrium near the superior vena cava, sends the impulse to the right and left atria myocardium. The nerves of the heart are cardiac branches of the vagus nerve fibers arising from trunks of the sympathetic nervous system. As with all other anatomical structures, the heart and lungs need nerves and blood vessels to accomplish their functions. ![]() The two major organs housed within the thorax are the heart and lungs. This is an excerpt from Kinetic Anatomy 4th Edition With HKPropel Access by Robert S.
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