Peak performance T7

Question 1

Describe a difference in the structure of muscle in a marathon runner, and a sprinter.
(1)

Answer 1

• More capillaries in marathon runner.
• More mitochondria in marathon runner.
• More myoglobin in marathon runner.

Question 2

How do you measure cardiac output? (volume of blood pumped by the heart in a minute)

Answer 2

CO=SV (stroke volume) x HR (heart rate)

Question 3

When running, adequate oxygen supply is maintained by:

Answer 3

• Increasing cardiac output.
• Faster rate of breathing.
• Deeper breathing.

Question 4

A person has a resting stroke volume of 75cm3. Their pulse rate is 70bpm. Calculate cardiac output.

Answer 4

SV x HR= 75 x 70; 5250 cm3 or 5.25 dm3 pm

Question 5

An athlete has a CO of 5.25 dm3, and a resting heart rate of 50bpm. Calculate SV.

Answer 5

5250cm3/50bpm=105 cm3=SV

Question 6

A patient had her CO measured, using a dilution technique in which a dye is injected into the circulation and sampled after circulation through the heart. His CO was measured at 4.1 dm3 pm. At the same time, his mean heart rate was recorded at 87bpm.

a) Explain how the CO might be determined from the concentration of dye in the sample taken after circulation through the heart.
b) Calculate SV, and suggest wether the patient should be referred for more tests, and why.

Answer 6

a) The concentration value gives a measure of stroke volume, which can be used when calculating CO, if we have the HR. The lower the concentration of dye in the sample, the larger the SV.
b) SV= 4100/87= 47 cm3 per heartbeat.
This is below the normal range, so yes to more tests.

Question 7

Wiggins has a heart rate of 188bpm during training, he states that he trains at 85% of his maximum HR. Calculate his maximum HR.

Answer 7

188 x 100= 18800

18800/85= 221bpm= 100%

Question 8

Why is the heart referred to as myogenic?

Answer 8

It can contract without external stimulation.

Question 9

Explain how changes in heart rate are brought about?

5

Answer 9

• Chemoreceptors in carotid artery/aortic body/medulla detect increase in CO2, and lowering of ph in the blood due to increase in H+ ions.
• Sends impulses to cardiovascular control centre.
• Releases neurotransmitter.
• Depolarising sinoatrial node.
• Increases rate of firing impulses.