Ventricles Function Parameters

Questions and Answers

What is the unit of measurement for stroke volume?

beats/min

mL (correct)

mL/min

Which of the following is NOT a factor that affects cardiac output?

Body metabolism

End-diastolic volume (correct)

Size of the body

Exercise

What is ejection fraction a measure of?

The effectiveness of the ventricles in ejecting blood (correct)

The total volume of blood ejected by the left ventricle per unit time

The number of beats per minute

The volume of blood ejected out of the left ventricle during each systolic cardiac contraction

What is the formula to calculate cardiac output?

Stroke volume x Heart rate Signup and view all the answers

What happens to ejection fraction when contractility increases?

It increases Signup and view all the answers

What is the normal value of ejection fraction?

60% Signup and view all the answers

How can cardiac output be increased?

By increasing stroke volume, heart rate, or both Signup and view all the answers

What is the difference between end-diastolic volume and end-systolic volume?

Stroke volume Signup and view all the answers

The function of the ventricles can be described by 3 parameters. These are:

Stroke volume, ejection fraction and cardiac output. Signup and view all the answers

End Diastolic volume is described as:

The volume of blood in the ventricle before ejection Signup and view all the answers

End Systolic volume can be described as:

the volume of blood remaining in the ventricle after ejection Signup and view all the answers

The ejection fraction is an indicator of contractility

True Signup and view all the answers

What is cardiac output?

The total volume of blood ejected by the left ventricle per unit of time (ml/min) Signup and view all the answers

Which of the following can increase stroke volume?

Increasing end-diastolic volume or decreasing end-systolic volume Signup and view all the answers

What is the effect of increased contractility on stroke volume?

It increases stroke volume Signup and view all the answers

Which of the following is NOT a factor that affects stroke volume?

Heart rate Signup and view all the answers

If end-diastolic volume is increased, what will happen to stroke volume?

It will increase Signup and view all the answers

What is the relationship between end-diastolic volume and stroke volume?

End-diastolic volume is directly proportional to stroke volume Signup and view all the answers

What determines the resting length from which the cardiac muscle contracts?

The stretching of the cardiac myocytes before contraction Signup and view all the answers

Preload is mainly determined by:

Diastolic filling and venous return Signup and view all the answers

What is the benefit of determining preload in cardiac function?

It determines the resting length from which the muscle contracts Signup and view all the answers

Which of the following best describes preload?

The pressure acting to stretch LV fibers at end-diastole Signup and view all the answers

Why is it important to understand preload in cardiac function?

It helps to understand how the cardiac muscle contracts Signup and view all the answers

Study Notes

Ventricular Function

Ventricular function is described by three key parameters: stroke volume, ejection fraction, and cardiac output.

Stroke Volume

Stroke volume is the volume of blood (in mL) ejected out of the left ventricle during each systolic cardiac contraction.
It is the difference between end-diastolic volume (volume of blood in the ventricle before ejection) and end-systolic volume (volume of blood remaining in the ventricle after ejection).

Ejection Fraction

Ejection fraction is the fraction (%) of the end-diastolic volume that is ejected in one stroke volume.
It describes the effectiveness of the ventricles in ejecting blood.
Normal ejection fraction is around 60% (0.6).
An increase in ejection fraction reflects an increase in contractility.
A decrease in ejection fraction reflects a decrease in contractility.

Cardiac Output

Cardiac output is the total volume of blood ejected by the left ventricle per unit time (in mL/min).
It depends on stroke volume and heart rate.
Cardiac output (mL/min) = stroke volume (mL) x heart rate (beats/min).
Cardiac output varies widely with body metabolism, exercise, age, and body size.
Cardiac output can only be increased if stroke volume increases, heart rate increases, or both increase.

Factors Affecting Stroke Volume

Stroke volume can only be increased by either increasing end-diastolic volume or decreasing end-systolic volume
Three primary factors affect stroke volume:
- Preload: influences stroke volume by modifying end-diastolic volume
- Contractility: affects stroke volume by altering the heart's ability to contract and pump blood
- Afterload: impacts stroke volume by affecting the resistance against which the heart pumps blood

Preload in the Heart

Preload is the pressure acting to stretch left ventricular (LV) fibers at end-diastole.
It involves the stretching of cardiac myocytes before contraction, which determines the resting length from which the muscle contracts.
Preload can be expressed in terms of LV end-diastolic pressure or end-diastolic volume.
The two main determinants of preload are:
- Diastolic filling
- Venous return

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Description

This quiz covers the parameters that describe the function of the ventricles, including stroke volume, ejection fraction, and cardiac output. Learn how these parameters are calculated and their significance in cardiac physiology.