Question

5. Consider the following equation:

Stroke volume = cardiac output / heart rate

If a heart fills up to 200ml of blood before contraction, and leaves 50ml in the heart after contraction, what would be the stroke volume? If the heart rate is 80 beats per minute, what would the calculated cardiac output? If the total peripheral resistance increases, what is likely to happen to the stroke volume? (Please address all three questions and include units to receive full credit.)
6.) Ralph is taking scuba diving classes, and is warned not to hold his breath when ascending from depth but to continuously release air from his mouth. What is the basis of this instruction and what is the risk if it is ignored? (10pts)

Answer 1

Stroke volume = cardiac output / heart rate

• If a heart fills up to 200ml of blood before contraction, and leaves 50ml in the heart after contraction,- The stroke volume would be:

(200-50) ml/beat = 150 ml/beat

• If the heart rate is 80 beats per minute, The calculated cardiac output would be:

Cardiac output(CO)= Heart Rate(HR) * Stroke Volume(SV)

= 80 beat/minute * 150 ml/beat

= 1200 ml/minute

=12 litre/minute

• If the total peripheral resistance increases, the stroke volume will go down.

6. The answer is in the following picture:

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