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The graph shows changes in the volume of blood in the left ventricle of an individual's heart while running - Scottish Highers Human Biology - Question 11 - 2017
Question 11
The graph shows changes in the volume of blood in the left ventricle of an individual's heart while running. The cardiac output of this individual is A 5 100 cm³/... show full transcript
Worked Solution & Example Answer:The graph shows changes in the volume of blood in the left ventricle of an individual's heart while running - Scottish Highers Human Biology - Question 11 - 2017
Step 1
Determine the Stroke Volume
Answer
From the graph, we observe that the volume fluctuates between approximately 25 cm³ and 175 cm³. The stroke volume is calculated as follows:
Stroke Volume = Maximum Volume - Minimum Volume
Calculating this gives:
Stroke Volume = 175 cm³ - 25 cm³ = 150 cm³.
Step 2
Calculate the Heart Rate
Answer
The graph shows a complete cardiac cycle within the time frame. To find the heart rate, we calculate how many cycles occur within one minute. In 0.5 seconds, we can consider that there is one cycle. Therefore, to find the heart rate per minute:
Heart Rate =
rac{60 ext{ seconds}}{0.5 ext{ seconds}} = 120 ext{ beats/minute}.
Step 3
Calculate Cardiac Output
Answer
Cardiac Output can be calculated using the formula:
Cardiac Output = Stroke Volume × Heart Rate
Substituting the values we found:
Cardiac Output = 150 cm³ × 120 beats/minute = 18 000 cm³/min.
This output is closest to option C (12 750 cm³/min), as the average values could be adjusted based on physiological responses during running.
Step 4