The relationship between cardiac output, stroke volume and HR

Question 1

Define cardiac cycle

Answer 1

• Diastole phase: when the heart relaxes and fills with blood.
• Systole phase: when the heart contracts and sends blood to the body and lungs.

Question 2

Define Venous return

Answer 2

• The volume of blood returning to the heart.

Question 3

Define Hypertrophy

Answer 3

• Muscle mass increasing in an organ/ muscle.

Question 4

Define ejection fraction

Answer 4

• The percentage of blood pumped out of the left ventricle per beat.

Question 5

Define bradycardia

Answer 5

• A decrease in resting HR below 60 bpm.

Question 6

Why has stroke volume increased in a trained individual Pt.1

Answer 6

1. Increased Venous Return= Increased SV
   - More blood in= more blood out.
2. Increased ejection fraction= Increased SV
   - An increase in venous return also leads to a greater ejection fraction.

Average person= 60% Trained athlete= as high as 85%

Question 7

Why has stroke volume increased in a trained individual Pt. 2

Answer 7

1. Cardiac hypertrophy= Increased SV
   - Increased muscle mass leads to more powerful contractions.
   - This obviously leads to an increased ejection fraction.
2. Starlings law= Increased SV
   - Starlings law states that the greater the venous return, the greater the FORCE of contraction.
   - The reason why is because…..
   -> When blood enters the heart it stretches the cardiac fibres. The more they stretch the greater the ejection fraction will be (elastic band).

Question 8

What is Starlings Law?

Answer 8

1. Increased venous return.
2. Greater diastolic filling.
3. Cardiac muscle stretched.
4. More force of contraction.
5. Increased ejection fraction.

Question 9

How much blood does the body require at rest?

Answer 9

• At rest the body requires 5 litres of blood pumped around it per minute.
• Therefore the Q of both a trained and an untrained individual will be the same (5 litres).