21 Review

• Match. Cardiac muscle cells.

  functional syncytium
• Match. Bradycardia.

  slow heart rate
• Match. Diastole.

  relaxation phase of the cardiac cycle
• Match. Coronary circulation.

  supplies blood to heart muscle
• Match. Visceral layer of serous pericardium.

  covers outer surface of the heart
• Match. Systole.

  contraction phase of the cardiac cycle
• Match. Myocardium.

  muscular wall of the heart
• Match. Right pulmonary vein.

  vein to the left atrium
• Match. Superior vena cava.

  vein to the right atrium
• Match. Parietal pericardium.

  lines inner surface of fibrous pericardium
• The potential space between the parietal and visceral layers of serous pericardium is the . . .

  pericardial cavity
• Label YELLOW: superior vena cava

  
• Label GREEN: interventricular septum

  
• Label BLUE: pulmonary trunk

  
• Label PURPLE: left common carotid artery

  
• The heart is innervated by . . .

  Both sympathetic and parasympathetic nerves.
• The pacemaker cells of the heart are located in . . .

  the SA node
• The two main branches of the right coronary artery (RCA) are the . . .

  Right marginal branch and the posterior interventricular branch.
• The cardiac skeleton of the heart has which two of the following functions?

  It physically isolates the muscle fibers of the atria from those of the ventricles AND it maintains the normal shape of the heart.
• If the papillary muscles fail to contract . . .

  The AV valves will not close properly.
• If there were damage to the sympathetic innervation to the heart, what would happen to the heart rate under the influence of the remaining autonomic nervous system stimulation?

  It would decrease.
• How is cardiac muscle similar to skeletal muscle?

  Cardiac muscle cells are like skeletal muscle fibers in that each cardiac muscle cell contains organized myofibrils, and the alignment of their sarcomeres gives the cardiac tissue a striated appearance.
• Why do the aortic and pulmonary valves lack muscular braces like those found in AV valves?

  The aortic and pulmonary valves do not require muscular braces because the arterial walls do not contract, and the relative positions of the cusps are stable.
• Define a pacemaker cell, and list the group of cells that normally serve as the heart's pacemaker, as well as those other cells that have the potential to serve as a pacemaker.

  A pacemaker cell is a cell that depolarizes spontaneously. The normal pacemaker cells (SA node) depolarize at the fastest rate. Other groups of cells that have the potential to serve as pacemaker cells are the atrioventricular node, AV bundle, right bundle branch, left bundle branch, and Purkinje fibers.
• What is the function of the pericardial fluid?

  Pericardial fluid is secreted by pericardial membranes and acts as a lubricant, reducing friction between the opposing visceral and parietal pericardial surfaces.
• Which chamber of the heart has the thickest walls? Why are its walls so thick?

  The left ventricle has the thickest walls because it needs to exert so much force to push blood around the systemic circuit.
• Why are nodal cells unique? What is their function?

  Nodal cells are unique because their plasma membranes depolarize spontaneously. Specific types of nodal cells called pacemaker cells are responsible for establishing the rate of cardiac contraction.
• Describe the function of the SA node in the cardiac cycle. How does this function differ from that of the AV node?

  The SA node, which is composed of cells that exhibit rapid pacemaker potential, is the pacemaker of the heart. The AV node slows the impulse that signals contraction because its cells are smaller than those of the conduction pathway.