Cardiovascular System MCQ Quiz - Objective Question with Answer for Cardiovascular System - Download Free PDF
Latest Cardiovascular System MCQ Objective Questions
Cardiovascular System Question 1:
The time taken for atrial systole and diastole in a normal heart are tas and tad seconds, respectively. If ventricular systole takes tvs seconds, calculate the ventricular diastolic time (seconds)
Answer (Detailed Solution Below)
Option 1 : (t as + t ad ) - t vs
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Cardiovascular System Question 1 Detailed Solution
The correct answer is (tas+ tad) - tvs
Explanation:
The cardiac cycle consists of a series of events that occur from the beginning of one heartbeat to the beginning of the next. It includes phases of systole (contraction) and diastole (relaxation) of both the atria and ventricles to ensure efficient blood flow through the heart, to the lungs, and to the rest of the body. The duration of these phases needs to be synchronized for the heart to function effectively.
- Atrial Systole and Diastole (AS + AD): This period includes the time when the atria contract (atrial systole) to push blood into the ventricles and the time when the atria are relaxed and filling with blood (atrial diastole).
- Ventricular Systole and Diastole (VS + VD): This period encompasses the time when the ventricles contract (ventricular systole) to eject blood into the arteries (systemic and pulmonary circulation) and the time when the ventricles are relaxed and filling with blood (ventricular diastole).
- Atrial Systole (AS): This is the phase where the atria contract to push blood into the ventricles. It's relatively short, lasting about 0.1 seconds. Atrial systole occurs late in the ventricular diastole phase, which assists in topping off the volume of the ventricles before they contract.
- Atrial Diastole (AD): Following atrial systole, the atria enter a relaxation phase, or diastole, which lasts for the remainder of the cardiac cycle. Given that the average total duration of the cardiac cycle is around 0.8 seconds (at a heart rate of 75 beats per minute), and subtracting the time for atrial systole, atrial diastole approximately accounts for the remaining 0.7 seconds in a broad sense across different phases of the ventricles. However, it's worth noting that the atria are in a state of relaxation even as the ventricles contract and undergo their cycles.
- Ventricular Systole (VS): This phase follows atrial systole and is divided into two parts: the isovolumetric contraction phase and the ventricular ejection phase. Overall, ventricular systole lasts about 0.3 seconds. During this phase, the ventricles contract, increasing pressure inside them and ejecting blood into the pulmonary artery and aorta.
- Ventricular Diastole (VD): After ventricular systole, the ventricles relax during ventricular diastole, which is also divided into two phases: isovolumetric relaxation and ventricular filling. This phase lasts approximately 0.5 seconds. It's during this phase that the ventricles fill with blood from the atria, preparing for the next cardiac cycle.The total cardiac cycle is the sum of all these times, as well as the ventricular diastole, which we need to calculate.
The total duration of the cardiac cycle can also be viewed as the sum of the durations of atrial systole, atrial diastole, and ventricular systole, plus the ventricular diastole time \(\)
Therefore, the formula for the total cardiac cycle time ttotaL can be written as:
\( t_ = tas + tad + tvs + t_ \)
We can rearrange this equation to solve for the ventricular diastole time tvd:
\(t_ = t_ - (tas + tad + tvs) \)
Assuming that the total duration of the cardiac cycle is equal to one complete cycle of atrial systole plus atrial diastole (since atrial and ventricular phases overlap slightly but can be considered approximately equal for simplicity), then:
\( t_ = tas + tad \)
Using this in our earlier formula for tvd, we get \(t_ = (tas + tad) - tvs \)
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Cardiovascular System Question 2:
For a normal heart, the time taken for atrial systole and diastole are AS and AD seconds respectively, while the same for ventricular systole and diastole are VS and VD. Which one of the following equations is correct?
Answer (Detailed Solution Below)
Option 1 : AS + AD = VS + VD
Cardiovascular System Question 2 Detailed Solution
The correct answer is A S + A D = V S + V D
Explanation:
The cardiac cycle consists of a series of events that occur from the beginning of one heartbeat to the beginning of the next. It includes phases of systole (contraction) and diastole (relaxation) of both the atria and ventricles to ensure efficient blood flow through the heart, to the lungs, and to the rest of the body. The duration of these phases needs to be synchronized for the heart to function effectively.
- Atrial Systole and Diastole (AS + AD): This period includes the time when the atria contract (atrial systole) to push blood into the ventricles and the time when the atria are relaxed and filling with blood (atrial diastole).
- Ventricular Systole and Diastole (VS + VD): This period encompasses the time when the ventricles contract (ventricular systole) to eject blood into the arteries (systemic and pulmonary circulation) and the time when the ventricles are relaxed and filling with blood (ventricular diastole).
- Atrial Systole (A S ): This is the phase where the atria contract to push blood into the ventricles. It's relatively short, lasting about 0.1 seconds. Atrial systole occurs late in the ventricular diastole phase, which assists in topping off the volume of the ventricles before they contract.
- Atrial Diastole (AD): Following atrial systole, the atria enter a relaxation phase, or diastole, which lasts for the remainder of the cardiac cycle. Given that the average total duration of the cardiac cycle is around 0.8 seconds (at a heart rate of 75 beats per minute), and subtracting the time for atrial systole, atrial diastole approximately accounts for the remaining 0.7 seconds in a broad sense across different phases of the ventricles. However, it's worth noting that the atria are in a state of relaxation even as the ventricles contract and undergo their cycles.
- Ventricular Systole (VS): This phase follows atrial systole and is divided into two parts: the isovolumetric contraction phase and the ventricular ejection phase. Overall, ventricular systole lasts about 0.3 seconds. During this phase, the ventricles contract, increasing pressure inside them and ejecting blood into the pulmonary artery and aorta.
- Ventricular Diastole (VD): After ventricular systole, the ventricles relax during ventricular diastole, which is also divided into two phases: isovolumetric relaxation and ventricular filling. This phase lasts approximately 0.5 seconds. It's during this phase that the ventricles fill with blood from the atria, preparing for the next cardiac cycle.
The total time taken for atrial systole and diastole is equal to the total time taken for ventricular systole and diastole.
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Cardiovascular System Question 3:
The blood volume of an individual is 5 litres. The person was injected with 500 mg of a drug that has molecular weight of 100 Da. If the drug is metabolized so that half of the drug remains in the bloodstream after every passing hour, the concentration of the drug four hours after injection is:
- 0.5 mM
- 0.25 mM
- 0.125 mM
- 0.0625 mM
Answer (Detailed Solution Below)
Option 4 : 0.0625 mM
Cardiovascular System Question 3 Detailed Solution
The correct answer is 0.0625 mM
Explanation:
Find the initial concentration:
- The initial amount of drug injected is 500 mg.
- The molecular weight of the drug is 100 Da (100 g/mol)
Convert the mass of the drug to moles:
Given that the blood volume is 5 liters, the initial concentration (C0) is:
- Initial concentration: \(\frac= 0.001 mol/L = 1 mM\)
Determine the concentration after each hour:
Initial concentration C0 = 1 mM
- After 1 hour: \( \frac\) = 0.5 mM
- After 2 hours: \( \frac\) = 0.25 mM
- After 3 hours: \( \frac\) = 0.125 mM
- After 4 hours: \( \frac\) = 0.0625 mM
Therefore, the concentration of the drug four hours after the injection is: 0.0625 mM
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Cardiovascular System Question 4:
Given below are the different intervals/ durations of electrocardiogram of a human subject (column A) and the events in heart during the process (column B).
COLUMN A | COLUMN B |
a. | PR interval | i. | Ventricular action potential |
b. | QRS duration | ii. | Atrioventricular conduction |
c. | QT interval | iii. | Ventricular depolarization |
d. | ST interval | iv. | Plateau portion of the ventricular action potential |
Which one of the following options is a correct match of entries in columns A and B?
- a - i; b - iv; c - ii; d - iii
- a - ii: b - iii; c - i; d - iv
- a - iv; b - ii; c - iii; d - i
- a - iii; b - i; c - iv, d - li
Answer (Detailed Solution Below)
Option 2 : a - ii: b - iii; c - i; d - iv
Cardiovascular System Question 4 Detailed Solution
The correct answer is Option 2 i.e. a - ii: b - iii; c - i; d - iv
Explanation-
- The QRS complex represents rapid ventricular depolarization, as the action potential spreads through ventricular contractile fibers.
- The S–T segment, which begins at the end of the S wave and ends at the beginning of the T wave, represents the time when the ventricular contractile fibers are depolarized during the plateau phase of the action potential. PR includes both atria and ventricular conduction.
- The P wave represents atrial depolarization, which spreads from the SA node through contractile fibers in both atria.
- The second wave, called the QRS complex, begins as a downward deflection, continues as a large, upright, triangular wave, and ends as a downward wave. The QRS complex represents rapid ventricular depolarization.
- The Q–T interval extends from the start of the QRS complex to the end of the T wave. It is the time from the beginning of ventricular depolarization to the end of ventricular repolarization.
Key Points The electrocardiogram (ECG or EKG) is a graphical representation of the electrical activity of the heart over time. Different intervals and durations are measured on the ECG to assess the cardiac cycle. Here are some of the key intervals and durations observed in a typical human electrocardiogram:
P Wave: Represents atrial depolarization, or the contraction of the atria.
- Duration: Usually around 80 milliseconds.
PR Interval : Represents the time it takes for the electrical impulse to travel from the atria to the ventricles.
- Duration: Normal range is 120 to 200 milliseconds.
QRS Complex: Represents ventricular depolarization, or the contraction of the ventricles.
- Duration: Typically less than 120 milliseconds.
ST Segment: Represents the early part of ventricular repolarization.
- Duration: Normally isoelectric (flat).
T Wave: Represents ventricular repolarization.
- Duration: Typically around 160 milliseconds.
QT Interval: Represents the total time for ventricular depolarization and repolarization.
- Duration: Varies with heart rate, corrected QT (QTc) is used to account for heart rate variations.
These durations can vary among individuals and may be influenced by factors such as age, sex, and overall health. It's important to note that abnormalities in these intervals can indicate various cardiac conditions and are used in the diagnosis and monitoring of heart diseases.
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Cardiovascular System Question 5:
Which ONE of the following graphs represents the relationship between ventricular end-diastolic volume and cardiac output in a healthy adult individual at rest (solid line) and upon exercise (dotted line)?
Answer (Detailed Solution Below)
Option 1 :
Cardiovascular System Question 5 Detailed Solution
The correct answer is Option 1
Concept:
The Frank-Starling mechanism (also known as the Frank-Starling law of the heart) is a fundamental principle in cardiovascular physiology describing the relationship between the volume of blood filling the heart (end-diastolic volume) and the heart's ability to eject blood during systole (stroke volume). In essence, the Frank-Starling mechanism states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the venous return) up to a physiological limit. This process enables the heart to automatically adjust its pumping capacity to accommodate varying volumes of venous return, ensuring a balanced output between the right and left ventricles and maintaining an equilibrium of blood flow in the circulatory system.
Explanation:
Each graph represents the relationship between ventricular end-diastolic volume and cardiac output in a healthy adult individual at rest (solid line) and upon exercise (dotted line).
- Graph 1 shows an increasing solid line and an even higher increasing dotted line. This suggests that at rest, as the ventricular end-diastolic volume increases, the cardiac output also increases. The increase is more pronounced during exercise, indicating enhanced cardiac performance with exercise, which is consistent with the Frank-Starling law. This law states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart.
- Graph 2 also shows increasing lines, but the dotted line for exercise starts to plateau. This could imply that there is a limit to how much exercise can increase cardiac output before it reaches a maximum capacity, possibly due to the heart's limited ability to increase its rate and force of contraction.
- Graph 3 indicates a slight increase in cardiac output with an increase in ventricular end-diastolic volume at rest. However, the dotted line for exercise shows a decrease beyond a certain volume. This is not typical of normal cardiac physiology and suggests a pathophysiological condition such as cardiac tamponade or heart failure where increased heart volume doesn't translate to increased output due to the heart's inability to pump effectively.
- Graph 4 depicts a constant cardiac output regardless of the ventricular end-diastolic volume both at rest and during exercise, which is not physiologically normal for a healthy individual. This could represent a scenario of severe heart dysfunction where the heart's output is fixed and cannot respond to changes in volume or the demands of exercise.
Conclusion:
The most physiologically accurate graph for a healthy individual both at rest and upon exercise is likely the first graph. It demonstrates the normal behavior of the heart under both conditions according to the Frank-Starling mechanism.