W4-L6: Functional Capacity of CVD System

Question 1

What is Cardiac Output?
What are the normal values in men and women?

Answer 1

Question 2

What is the Direct Fick Method?

Answer 2

Question 3

Training and Cardiac Output (Q)

Answer 3

A trained individual will have a lower resting HR but a higher stroke volume

Question 4

Cardiac Output: Endurance Athletes

Answer 4

Resting HR of healthy endurance athletes = 50 b/min at rest and resting SV = 100 mL/b

Question 5

What Factors explain large SV and low HR of endurance trained athletes?

Answer 5

1) Increased vagal tone and decreased sympathetic drive, both of which slow the heart

2) Increased blood volume, myocardial contractility, and compliance of the left ventricle, all of which augment the heart’s stroke volume

Question 6

How is blood flow affected during PA?

Answer 6

• Systemic blood flow increases directly with intensity of physical activity
• Cardiac output increases rapidly during the transition from rest to steady-rate exercise and then rises gradually until it plateaus when metabolic requirements

Question 7

What is Stroke volume?

Answer 7

Question 8

What is preload?

Answer 8

Preload is the degree of stretch of the cardiac muscle fibers at the end of diastole, determined by the volume of blood returning to the heart.

Question 9

What is Enhanced Diastolic Filling?

Answer 9

• Any factor that increases venous return or slows the heart produces greater preload during the cardiacm cycle’s diastolic phase
• An increase in end-diastolic volume stretches myocardial fibers and initiates a more powerful ejection stroke during systole
• Ejects the normal SV plus additional blood that entered ventricles during diastole

Question 10

What is the Frank-Starling law?

Answer 10

The Frank-Starling law states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (end-diastolic volume), due to the myocardial fibers being stretched to a more optimal length for contraction

• Within physiological limits, the force of contraction is directly propotional to the initial length of the muscle fiber

Question 11

Frank Starling Mechanism

Answer 11

The Frank Starling mechanism states that the energy of contraction is proportional to the initial length of the cardiac muscle fiber
An increased contraction accompanying increased EDV or ventricular stretch

Question 12

What is Greater Systolic Emptying?

Answer 12

During exercise, enhanced systolic emptying occurs despite increased afterload (resistance due to higher systolic BP) because:

1. Functional Residual Volume: Ventricles always have a residual blood volume (~40%, or 50-70mL) to pump.
2. Catecholamines: Release of catecholamines during exercise increases myocardial contractility, augmenting stroke power and facilitating more complete systolic emptying.

Question 13

What is Cardiovascular drift?

Answer 13

Cardiovascular drift is a gradual, time-dependent phenomenon during prolonged steady-state exercise where submaximal exercise for more than 15 minutes decreases plasma volume and stroke volume (SV), particularly in the heat. To maintain cardiac output, the body compensates by increasing heart rate (HR).