Question 1

The SA node impulses result in:&#10;A) diastole.&#10;B) depolarization.&#10;C) repolarization.&#10;D) All of the above

Accepted Answer

The SA node impulses initiate a wave of depolarization that spreads throughout the atria, causing them to contract. This wave of depolarization is responsible for the initiation of the cardiac cycle, which leads to the opening of the AV valves and the onset of systole. Diastole occurs when the heart is at rest, and repolarization occurs when the cell membrane returns to its resting potential following depolarization. While diastole and repolarization are both important components of the cardiac cycle, they are not directly initiated by the SA node impulses.

Question 2

The internodal tracts consist of anterior,middle,and posterior. They are also known as all of the following EXCEPT:&#10;A) Bachmann's bundle.&#10;B) Thorel's pathway.&#10;C) Wenckebach's bundle.&#10;D) Beasley's pathway.

Accepted Answer

Beasley's pathway is not a recognized term for any of the internodal tracts within the heart's conduction system. Bachmann's bundle, Thorel's pathway, and Wenckebach's bundle are all recognized names for parts of the internodal pathways.

Question 3

Which part of the conduction system has a firing rate of 60 to 100?&#10;A) SA node&#10;B) Purkinje fibers&#10;C) AV node&#10;D) Bundle branches

Accepted Answer

The SA node, or sinoatrial node, is the natural pacemaker of the heart and has a firing rate of 60 to 100 beats per minute. This is the highest firing rate of any part of the conduction system.

Question 4

The area where the internodal pathways join the bundle of His is:&#10;A) Purkinje's network.&#10;B) the left bundle branch.&#10;C) the AV junction.&#10;D) the right bundle branch.

Accepted Answer

The internodal pathways transmit the electrical impulse from the sinoatrial node to the atrioventricular (AV) node, which is located near the bottom of the right atrium. The AV junction is the area where the internodal pathways join the bundle of His before transmitting the impulse to the ventricles via the bundle branches and Purkinje's network. Therefore, C is the best choice.

Question 5

If the vagus nerve is stimulated,the heart rate will:&#10;A) increase.&#10;B) decrease.

Accepted Answer

When the vagus nerve is stimulated, it releases acetylcholine which slows down the heart rate, thereby decreasing it.

Question 6

Bachmann's bundle is located in the:&#10;A) left atrium.&#10;B) right ventricle.&#10;C) top of right atrium.&#10;D) left ventricle.

Accepted Answer

Bachmann's bundle is an important structure in the heart located in the left atrium. It is a band of cardiac muscle fibers that plays a crucial role in conducting electrical impulses from the atria to the ventricles, specifically facilitating the conduction of impulses between the right and left atria, thus helping to synchronize atrial contraction.

Question 7

It is generally believed that a bit less than ________ of the cells are actual pacemaker cells.&#10;A) 50%&#10;B) 25%&#10;C) 85%&#10;D) 75%

Accepted Answer

The sinoatrial (SA) node is the primary pacemaker of the heart, but it is estimated that only about 1% of the total number of cells in the heart are actually pacemaker cells. The remaining cells in the heart contribute to various functions such as contraction and conduction of electrical impulses. Therefore, choice A) 50% is the closest estimation of the number of pacemaker cells.

Question 8

The pacemaker that fires at 20 to 40 beats per minute is:&#10;A) the SA node.&#10;B) the bundle of His.&#10;C) the AV node.&#10;D) Purkinje's network.

Accepted Answer

Purkinje's network is responsible for the final part of the electrical conduction system of the heart and can fire at a rate of 20 to 40 beats per minute if higher pacemakers fail.

Question 9

Nodes and bundles are located primarily beneath the:&#10;A) myocardium.&#10;B) epicardium.&#10;C) pericardium.&#10;D) endocardium.

Accepted Answer

Nodes and bundles, including the sinoatrial node and atrioventricular node, are located within the heart muscle and primarily beneath the endocardium, the innermost layer of the heart lining.

Question 10

The three-lead EKG strip is representative of the mechanical activity of the heart.

Accepted Answer

The three-lead EKG strip is representative of the electrical activity of the heart, not the mechanical activity.

Question 11

The bundle of His is also traditionally referred to as the ________ bundle.&#10;A) universal&#10;B) simple&#10;C) common&#10;D) dedicated

Accepted Answer

The answer of The bundle of His is also traditionally...

Question 12

The node that is located just above the tricuspid valve is the:&#10;A) AV node.&#10;B) SA node.&#10;C) Purkinje node.&#10;D) central node.

Accepted Answer

The answer of The node that is located just above...

Question 13

A(n)________ pathway may be defined as an irregular muscle connection between the atria and the ventricles that bypasses the AV node.&#10;A) universal&#10;B) Thorel's&#10;C) accessory&#10;D) conductive

Accepted Answer

The answer of A(n)________ pathway may be defined as an...

Question 14

The bundle of His lies at the ________ of the interventricular septum.&#10;A) bottom&#10;B) top&#10;C) right&#10;D) left

Accepted Answer

The answer of The bundle of His lies at the...

Question 15

In the normal heart,this is the ONLY pathway between the atria and ventricles.&#10;A) Right bundle branch&#10;B) SA node&#10;C) AV node&#10;D) Left bundle branch

Accepted Answer

The answer of In the normal heart,this is the ONLY...

Deck 4: The Electrical Conduction System