Question 1

Which phase of the normal myocardial cell depolarization and repolarization correlates with diastole?
A) Phase 0
B) Phase 1
C) Phase 2
D) Phase 3
E) Phase 4

Accepted Answer

Potassium is moved out of the cell during phase 3, with a return to resting membrane potential in phase 4. The time between action potentials corresponds to diastole.

Question 2

Within a physiologic range,an increase in left ventricular end-diastolic volume (preload)leads to a(n):
A) increased force of contraction.
B) decrease in refractory time.
C) increase in afterload.
D) increase in repolarization.

Accepted Answer

An increase in left ventricular end-diastolic volume (preload) leads to stretching of the myocardium, which is one of the factors regulating the force of contraction. This is known as the Frank-Starling mechanism, which states that the greater the stretch, the greater the force of contraction. Therefore, an increase in preload leads to an increased force of contraction.

Question 3

_____ nerves can shorten the conduction time of action potential through the atrioventricular (AV)node.
A) Parasympathetic
B) Sympathetic
C) Vagal
D) Glossopharyngeal

Accepted Answer

Sympathetic nerves can shorten the conduction time of action potential through the atrioventricular (AV)node. Parasympathetic nerves, on the other hand, can slow down the conduction time. Vagal and glossopharyngeal nerves are not directly involved in the conduction of action potentials through the AV node.

Question 4

What occurs during phase 1 of the normal myocardial cell depolarization and repolarization?
A) Repolarization when potassium moves out of the cells
B) Repolarization when sodium rapidly enters into cells
C) Early repolarization when sodium slowly enters cells
D) Early repolarization when calcium slowly enters cells

Accepted Answer

Early repolarization occurs when calcium slowly enters cells.

Question 5

Depolarization of a cardiac muscle cell occurs as the result of a:
A) decrease in the permeability of the cell membrane to potassium.
B) rapid movement of sodium into the cell.
C) rapid movement of calcium into the cell.
D) slow movement of sodium out of the cell.
E) slow movement of calcium out of the cell.

Accepted Answer

Depolarization of a cardiac muscle cell is caused by the rapid movement of sodium into the cell, which leads to a positive charge inside the cell and a negative charge outside. This triggers a series of events that leads to the contraction of the muscle cell.

Question 6

In the normal electrocardiogram,the PR interval represents:
A) atrial depolarization.
B) ventricular depolarization.
C) atrial activation to onset of ventricular activity.
D) "electrical systole" of the ventricles.

Accepted Answer

The PR interval represents the time from the onset of atrial depolarization (P wave) to the onset of ventricular depolarization (QRS complex), which reflects the conduction time from the atria to the ventricles. Therefore, it represents the duration of atrial activation to onset of ventricular activity.

Question 7

The _____ complex (wave)represents the sum of all ventricular muscle cell depolarization.
A) PRS
B) QRS
C) QT interval
D) P

Accepted Answer

The QRS complex represents the sum of all ventricular muscle cell depolarization.

Question 8

The cardiac electrical impulse normally begins spontaneously in the SA node because:
A) of its superior location in the right atrium.
B) it is the only area of the heart capable of spontaneous depolarization.
C) it has rich sympathetic innervation via the vagus nerve.
D) it depolarizes more rapidly than other automatic cells of the heart.

Accepted Answer

The SA node is capable of spontaneous depolarization because it has a unique ability to depolarize more rapidly than other automatic cells in the heart. This is due to its unique structure and ion channel distribution, which allows for the fastest depolarization rate.

Question 9

Where are the receptors for neurotransmitters located in the heart?
A) Semilunar and atrioventricular valves
B) Endocardium and sinoatrial node
C) Myocardium and coronary vessels
D) Epicardium and atrioventricular node

Accepted Answer

Sympathetic neural stimulation of the myocardium and coronary vessels depends on the presence of adrenergic receptors, which bind specifically with neurotransmitters of the sympathetic nervous system. The β₁-receptors are found mostly in the heart, specifically the conduction system (AV and SA nodes, Purkinje fibers) and the atrial and ventricular myocardium, whereas the β₂-receptors are found mostly on coronary arterioles and cause coronary vasodilation when stimulated by epinephrine.

Question 10

The coronary sinus empties into the:
A) right atrium.
B) left atrium.
C) superior vena cava.
D) aorta.

Accepted Answer

The coronary sinus is a large vein that collects blood from the heart's coronary veins and empties it into the right atrium of the heart.

Question 11

Which statement about development of collateral arteries in the heart is false?
A) The incidence of aneurysm formation after a myocardial infarction is reduced in individuals who develop significant collateral circulation.
B) The incidence of myocardial regeneration after a myocardial infarction increases in individuals who develop significant collateral circulation.
C) The risk of dysrhythmias after a myocardial infarction is reduced in individuals with well-developed collateral circulation.
D) Collateral circulation may extend the "window of time" to benefit reperfusion therapy after a myocardial infarction,resulting in greater improvement in cardiac function.

Accepted Answer

Currently, there is no evidence to support the statement that the development of collateral arteries increases myocardial regeneration after a myocardial infarction. While collateral circulation may provide a support structure for revascularization and limit the extent of ischemic damage, it does not directly increase myocardial regeneration.

Question 12

The _____ follows depolarization of the myocardium and represents a period during which no new cardiac potential can be propagated.
A) refractory period
B) hyperpolarization period
C) threshold period
D) SA period

Accepted Answer

During the refractory period, the myocardium is unable to propagate any new cardiac potential, even with a strong stimulus. This period follows depolarization and is necessary for the heart to properly contract and relax without interference.

Question 13

As stated by the Frank-Starling law,there is a direct relationship between the _____ of the blood in the heart at the end of diastole and the _____ of contraction during the next systole.
A) pressure;force
B) volume;strength
C) viscosity;force
D) viscosity;strength

Accepted Answer

The Frank-Starling law states that the greater the volume of blood in the heart during diastole, the greater the force of contraction during the next systole. Therefore, there is a direct relationship between volume and strength of contraction. Pressure and viscosity do not have a direct relationship with the Frank-Starling law.

Question 14

What enables electrical impulses to travel in a continuous cell-to-cell fashion in myocardial cells?
A) Sarcolemma sclerotic plaques
B) Intercalated disks
C) Trabeculae carneae
D) Bachmann bundles

Accepted Answer

Intercalated disks are specialized structures between myocardial cells that allow for the rapid and coordinated spread of electrical impulses, enabling the heart to contract as a unit. The other options (Sarcolemma sclerotic plaques, Trabeculae carneae, and Bachmann bundles) do not play a role in enabling electrical impulses to travel in a continuous cell-to-cell fashion in myocardial cells.

Question 15

Where are the coronary ostia located?
A) Left ventricle
B) Medial to the aortic valve
C) Coronary sinus
D) Aorta

Accepted Answer

The coronary ostia are located in the aorta, specifically in the aortic sinuses just above the aortic valve, where the coronary arteries originate.

Question 16

What is the ratio of coronary capillaries to cardiac muscle cells?
A) 1:1 (1 capillary per 1 muscle cell)
B) 1:2 (1 capillary per 2 muscle cells)
C) 1:4 (1 capillary per 4 muscle cells)
D) 1:10 (1 capillary per 10 muscle cells)

Accepted Answer

The ratio of coronary capillaries to cardiac muscle cells is approximately 1:1, meaning each cardiac muscle cell is closely associated with a capillary to ensure efficient oxygen and nutrient delivery.

Question 17

What is the function of P cells found in the sinoatrial node and Purkinje fibers?
A) They are receptors for pain stimuli,such as the pain that occurs during infarction.
B) They prolong the refractory period before the next contraction.
C) They are assumed to be the site of impulse formation.
D) They initiate repolarization of the myocardium.

Accepted Answer

P cells found in the sinoatrial node and Purkinje fibers are assumed to be the site of impulse formation, meaning they initiate the electrical impulses that stimulate cardiac muscle contraction. They are responsible for setting the pacemaker of the heart.

Question 18

What,if any,is the effect of epinephrine on b₂-receptors of the heart? A) None,b₁-receptors are the only b-receptors in the heart. B) Dilate coronary arterioles C) Increase the strength of myocardial contraction D) Increase the heart rate

Accepted Answer

Epinephrine binds to b₂-receptors in the heart, causing dilation of coronary arterioles.

Question 19

Phase 0 of the normal myocardial cell depolarization and repolarization correlates with which part of the electrocardiogram (EKG)?
A) QRS complex
B) P-R interval
C) Q-T interval
D) U wave

Accepted Answer

Phase 0 of myocardial cell depolarization corresponds to the rapid depolarization phase, which is represented by the QRS complex on the EKG.

Question 20

If the sinoatrial (SA)node fails,at what rate can the atrioventricular (AV)node polarize?
A) 60 to 70 per minute
B) 40 to 60 per minute
C) 30 to 40 per minute
D) 10 to 20 per minute

Accepted Answer

The atrioventricular (AV) node can polarize at a rate of 40 to 60 per minute if the sinoatrial (SA) node fails, but this is slower than the normal pacemaker rate of the SA node (60 to 100 per minute). This can lead to a slower heart rate known as bradycardia.

Quiz 28: Structure and Function of the Cardiovascular and Lymphatic Systems

Which phase of the normal myocardial cell depolarization and repolarization correlates with diastole?

Within a physiologic range,an increase in left ventricular end-diastolic volume (preload) leads to a(n) :

_____ nerves can shorten the conduction time of action potential through the atrioventricular (AV) node.

What occurs during phase 1 of the normal myocardial cell depolarization and repolarization?

Depolarization of a cardiac muscle cell occurs as the result of a:

In the normal electrocardiogram,the PR interval represents:

The _____ complex (wave) represents the sum of all ventricular muscle cell depolarization.

The cardiac electrical impulse normally begins spontaneously in the SA node because:

Where are the receptors for neurotransmitters located in the heart?

The coronary sinus empties into the:

Which statement about development of collateral arteries in the heart is false?

The _____ follows depolarization of the myocardium and represents a period during which no new cardiac potential can be propagated.

As stated by the Frank-Starling law,there is a direct relationship between the _ of the blood in the heart at the end of diastole and the _ of contraction during the next systole.

What enables electrical impulses to travel in a continuous cell-to-cell fashion in myocardial cells?

Where are the coronary ostia located?

What is the ratio of coronary capillaries to cardiac muscle cells?

What is the function of P cells found in the sinoatrial node and Purkinje fibers?

What,if any,is the effect of epinephrine on b₂-receptors of the heart?

Phase 0 of the normal myocardial cell depolarization and repolarization correlates with which part of the electrocardiogram (EKG) ?

If the sinoatrial (SA) node fails,at what rate can the atrioventricular (AV) node polarize?