Cardiac funtion Flashcards
Define the terms cardiac output and stroke volume and explain the relationship between them ( 3 marks)
Cardiac output is the amount of blood pumped out of the left ventricle in one minute. Stroke volume is the amount of blood pumped out of the heart per beat.
Cardiac output = stroke volume x heart rate
Use Starling’s law of the heart to explain how stroke volume increases during activity ( 3 marks)
Starlings law is the contractibility of the cardiac fibres. Increasing the stretch of the cardiac muscles when your exercising means that stroke volume will increase and ejection fraction will increase as well. This means that there is a stronger force of contraction, additionally venous return will increase.
What effect would a 6 month period of aerobic training have on the heart of soccer player? (3 marks)
The soccer player would experience hypertrophy meaning the heart would get bigger. Additionally they would experience bradycardia and athletes heart.
Explain the terms bradycardia and athletes heart (2 marks)
Bradycardia is when the athlete has a resting heart rate which is below 60 bpm.
Athletes heart is when the heart chambers increase in size.
What physiological factors are responsible for these conditions (3 marks)
- Increased Capillarisation
- Hypertrophy
- increased stroke volume
What are the effects of a period of training on resting stroke volume and cardiac output (2 marks)
The stroke volume would increase because the heart jas been trained. However the cardiac output would stay the same because it is resting.
How does a lower resting heart rate affect oxygen delivery to the muscles? (2 marks)
Because there is less oxygen needed for the heart contraction, so it means that more oxygen can be used for the muscles.
During exercise, heart rate increases to meet the extra oxygen demand required by the muscles. Explain how the increasing level of carbon dioxide in the blood increases heart rate. (3 marks)
Chemoreceptors detect the change in lactic acid and carbon dioxide, which sends a nerve impulse to the cardiac control centre in the medulla, which sends a nerve impulse down the sympathetic pathway to the SAN, to increase heart rate.
The heart rate increase prior to and during exercise, and reduces after the exercise. Explain how these changes in heart rate occur (4 marks)
Prior to exercise there is a release of adrenaline, which is called the anticipatory rise.
During exercise there will be an increase in movement which will be detected by the proprioceptors. Also there will be an increase in blood pressure, which will be detected by the baroceptors. These will send a nerve impulse to the cardiac control centre, which will then send a nerve impulse down the sympathetic pathway to the SAN, which will increase the heart rate.
After exercise there will be a change in lactic acid and carbon dioxide which will be detected by the chemoceptors, which will then send a nerve impulse to the cardiac control centre, which will then send an impulse down the parasynthetic pathway to the SAN, which will decrease the heart rate.
Just before the start of an 800 m race, an athlete will experience a change in heart rate. What change occurs in the athletes heart and why? (2 marks)
The athletes heart will increase and this is because adrenaline has been released into the body, which is known as the anticipatory rise. This happens so that the performer is ready to start.
