What factor most limits a person’s maximal increase in cardiac output during exercise?

Question

A.  the rate at which cardiac muscle contracts
B.  the time it takes for electrical impulses to reach all parts of the heart
C.  the total amount of blood in an individual
D.  the time available to fill the heart chambers with blood as the heart rate increases
E.  the rate at which oxygen is delivered to the cardiac muscle cells


Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?

Gather Content
What do you already know about the limiting factors on cardiac output? What other information is related to the question?
 
Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
  Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

D.  the time available to fill the heart chambers with blood as the heart rate increases

Clarify Question
What is the key concept addressed by the question?
        · The question is asking about the greatest limiting factor that impacts cardiac output during exercise.
What type of thinking is required?
        · Apply level:
            o You are being asked to take what you already know and use, or apply, it to the limitations of cardiac output.

Gather Content
What do you already know about the limiting factors on cardiac output? What other information is related to the question?
        · Cardiac output is equal to the stroke volume multiplied by beats per minute.
        · Stroke volume is the volume of blood that is moved by a ventricle with one contraction.
        · With exercise, heart rate increases.
        · The ventricles receive blood from the atria, which contract to fill relaxed ventricles.
 
Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
        · As heart rate increases, there is less time to fill ventricles.
        · As ventricles fill less, stroke volume and cardiac output decrease.
  Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        · Apply level:
            o Answering this question correctly depended on your ability to use cardiac output in a new situation. If you got an incorrect answer, did you remember that cardiac output is directly proportional to stroke volume, or that stroke volume is the volume of blood that is moved by a ventricle? Did you have trouble extending cardiac output to determine the correct answer?