Free medical quiz
Control of Cardiac Output Quiz
Focused SBA-style practice, followed by the answer and explanation for every question.
- Free now
- 5 questions
- Full bank
- 24 questions
- Answers
- Explained
Free question
Try one with the answer
A question from this quiz. Answer it to see the explanation students get.
Which statement best describes how cardiac output is determined under normal physiological conditions?
- A The volume of blood remaining in the ventricle after systole You picked ✕
- B The difference between systolic and diastolic blood pressure You picked ✕
- C The amount of blood ejected from the left ventricle per beat You picked ✕
- D The resistance that the ventricles pump against during systole You picked ✕
- E The product of heart rate and stroke volume You picked ✓
Correct!
Incorrect
The answer is E: The product of heart rate and stroke volume
Explanation
Why E is correct
See Cardiac Output. Option E is correct. Cardiac output is the volume of blood pumped by each ventricle in one minute, and it is calculated as heart rate (beats per minute) multiplied by stroke volume (the volume of blood ejected by one ventricle with each beat). For example, a resting heart rate of 70 beats per minute and a stroke volume of 70 mL gives a cardiac output of 4900 mL, or just under 5 litres, per minute. The equation is useful because it shows that the body can change its output in two ways. Heart rate is mainly controlled by the autonomic nervous system, with sympathetic activity speeding the sinoatrial node and vagal activity slowing it. Stroke volume depends on preload (how much the ventricle is stretched by filling), afterload (the resistance it pumps against) and contractility (the strength of the contraction at a given filling). In exercise, heart rate and stroke volume both rise, so output can increase several-fold. Memory aid: Output equals rate times stroke: beats per minute multiplied by the volume of each beat.
- Equation: Cardiac output equals heart rate multiplied by stroke volume.
- Heart rate: It is controlled mainly by the autonomic nervous system.
- Stroke volume: It depends on preload, afterload and contractility.
Why the other options are incorrect
- A. The volume of blood remaining in the ventricle after systole: The blood left in the ventricle after systole is the end-systolic volume. Subtracting it from the end-diastolic volume gives the stroke volume, so it is a step towards cardiac output and not its definition. Your answer
- B. The difference between systolic and diastolic blood pressure: The difference between the systolic and diastolic pressures is the pulse pressure. It is influenced by stroke volume, but it is a pressure and not a volume of blood per minute. Your answer
- C. The amount of blood ejected from the left ventricle per beat: The amount ejected from the ventricle with each beat is the stroke volume. Cardiac output also needs the number of beats per minute, so stroke volume alone is only one of its two components. Your answer
- D. The resistance that the ventricles pump against during systole: The resistance the ventricles pump against is the afterload, which is one of the factors that influences stroke volume. It describes a force to be overcome and does not measure how much blood leaves the heart. Your answer
With Premium, questions you miss become Revision Coach flashcards, scheduled for review.
Question preview
What you will practise
More questions from this set. Start the quiz to answer them and see each explanation.
-
1
Within the physiological filling range of a healthy heart, which statement best describes the Frank-Starling law?
-
2
Which mechanism best explains how increased sympathetic nervous system activity raises heart rate?
Revise before you test
Review SimpleMed's doctor-written article, then return here to check recall.
Read the topic articleNeed wider coverage?
Explore every Cardiovascular System topic set, or build a tailored mixed session.
Browse subject quizzes