Question 1

Mechanical activation of the heart occurs after electrical excitation because of the action of which of the following ions?&#10;A) Calcium&#10;B) Phosphorus&#10;C) Sodium&#10;D) Potassium&#10;

Accepted Answer

Calcium plays a crucial role in the mechanical activation of the heart. After the electrical excitation of the cardiac muscle cells, calcium ions enter the cells, triggering the myofilaments to contract and leading to the mechanical pumping action of the heart.

Question 2

Which of the following is an anticipated effect of increasing preload in the healthy heart?&#10;A) Decreased cardiac output&#10;B) Decreased myocardial work&#10;C) Increased stroke volume&#10;D) Increased heart rate&#10;

Accepted Answer

Increasing preload in a healthy heart increases the amount of blood that the heart can eject with each contraction, leading to an increased stroke volume. Choices A, B, and D are incorrect because increasing preload would not cause a decreased cardiac output, decreased myocardial work, or increased heart rate in a healthy heart.

Question 3

What is the anticipated effect of vagal stimulation on the heart?&#10;A) It shortens the refractory period&#10;B) It widens the QRS complex&#10;C) It slows the heart rate&#10;D) It increases the coronary blood supply&#10;

Accepted Answer

Vagal stimulation is known to slow down the heart rate by decreasing the firing rate of the sinoatrial (SA) node, which is the primary pacemaker of the heart. This effect is due to the release of acetylcholine by the vagus nerve, which activates muscarinic receptors in the SA node and reduces the activity of the funny current (If) channels that are responsible for the spontaneous depolarization of the nodal cells. As a result, the SA node takes longer to reach the threshold potential, and the heart rate decreases.

Question 4

Epinephrine and norepinephrine exert which of the following effects on the heart?&#10;A) Decrease the heart rate&#10;B) Increase force of myocardial contraction&#10;C) Decrease conduction velocity&#10;D) Lengthen the refractory period of the atrioventricular junction&#10;

Accepted Answer

Epinephrine and norepinephrine both act on adrenergic receptors in the heart, leading to an increase in the force of myocardial contraction (inotropy) and an increase in heart rate (chronotropy). They also increase conduction velocity and shorten refractory periods in the atrioventricular junction, thus increasing the risk of arrhythmias. However, the overall effect on the heart is to increase cardiac output. Choice A is incorrect because epinephrine and norepinephrine increase, not decrease, heart rate. Choices C and D are incorrect because they increase, not decrease, conduction velocity and shorten, not lengthen, the refractory period of the atrioventricular junction.

Question 5

Depolarization as a stage in the action potential of the heart can be seen in which of the following parts of the electrocardiogram?&#10;A) P wave&#10;B) PR interval&#10;C) QRS complex&#10;D) T wave&#10;

Accepted Answer

The QRS complex represents depolarization of the ventricles in the heart. The P wave represents the depolarization of the atria, the PR interval represents the time it takes for the electrical signal to travel from the atria to the ventricles, and the T wave represents repolarization of the ventricles.

Question 6

Which of the following properties is unique to cardiac pacemaker cells?&#10;A) Automaticity&#10;B) Rhythmicity&#10;C) Conductivity&#10;D) Refractoriness&#10;

Accepted Answer

Automaticity is the property of generating electrical impulses spontaneously, without external stimulation. This property is unique to cardiac pacemaker cells, as they are able to initiate and regulate the heartbeat. Rhythmicity, conductivity, and refractoriness are also properties of cardiac pacemaker cells, but are not unique to them, as other cardiac cells also possess these properties.

Question 7

Myocardial tissue is nonresponsive to stimulation during which phase of the cardiac cycle?&#10;A) The final phase of diastole&#10;B) The initial phase of systole&#10;C) The final phase of systole&#10;D) The initial phase of diastole&#10;

Accepted Answer

The initial phase of systole corresponds to the period of ventricular contraction when the myocardium is in a state of depolarization, leading to the absolute refractory period during which it cannot respond to further stimulation.

Question 8

Vagal stimulation of the heart leads to&#10;A) bradycardia.&#10;B) tachycardia.&#10;C) ventricular arrhythmias.&#10;D) atrial arrhythmias.&#10;

Accepted Answer

Vagal stimulation, also known as parasympathetic stimulation, causes a decrease in heart rate and ultimately leads to bradycardia.

Question 9

The cardiac output is the product of which of the following two variables?&#10;A) Stroke volume and peripheral vascular resistance&#10;B) Stroke volume and heart rate&#10;C) Heart rate and blood pressure&#10;D) Heart rate and peripheral vascular resistance&#10;

Accepted Answer

Cardiac output is the volume of blood pumped by the heart per unit time. It is calculated as the product of stroke volume (the amount of blood pumped out of the left ventricle per beat) and heart rate (the number of beats per minute). Therefore, the correct answer is B, as it includes both stroke volume and heart rate.

Question 10

The primary initiator of the conduction cycle in the heart is the&#10;A) Purkinje fibers.&#10;B) atrioventricular node.&#10;C) sinoatrial node.&#10;D) bundle of His.&#10;

Accepted Answer

The sinoatrial node (SA node) is the primary initiator of the conduction cycle in the heart. It is also known as the natural pacemaker of the heart. It is located in the right atrium and generates electrical impulses that spread throughout the heart and coordinate its contractions.

Question 11

The fundamental muscle unit responsible for myocardial contraction is the&#10;A) atrioventricular node.&#10;B) sinoatrial node.&#10;C) Purkinje fiber.&#10;D) sarcomere.&#10;

Accepted Answer

The answer of The fundamental muscle unit responsible for myocardial...

Question 12

The effective refractory period is when the heart cell&#10;A) may be stimulated by the atrioventricular node.&#10;B) cannot respond to a stimulus.&#10;C) can create a full action potential.&#10;D) responds repetitively.&#10;

Accepted Answer

The answer of The effective refractory period is when the...

Question 13

Which of the following tissues of the heart are not affected by cardiac drugs?&#10;A) The myocardium&#10;B) The pericardium&#10;C) The conduction system&#10;D) The coronary vessels&#10;

Accepted Answer

The answer of Which of the following tissues of the...

Question 14

The ability of the heart to beat regularly is referred to as which of the following properties of cardiac tissue?&#10;A) Automaticity&#10;B) Rhythmicity&#10;C) Conductivity&#10;D) Refractoriness&#10;

Accepted Answer

The answer of The ability of the heart to beat...

Question 15

Repolarization as a stage in the action potential of the heart can be seen in which of the following parts of the electrocardiogram?&#10;A) P wave&#10;B) PR interval&#10;C) QRS complex&#10;D) T wave&#10;

Accepted Answer

The answer of Repolarization as a stage in the action...

Deck 24: Overview of the Cardiovascular System