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4.2 Cardiac Output

Anatomy and Physiology11 CardsCreated 4 months ago

This flashcard set reviews key mechanisms that increase venous return to the heart, including the skeletal muscle pump, respiratory pump, and sympathetic nervous system. It also explains how sympathetic stimulation promotes venous return through vasoconstriction and increased pressure.

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What 3 mechanisms increase venous return of blood to the heart?

> Skeletal muscle pump
> Respiratory pump
> Sympathetic Nervous System

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Key Terms

Term
Definition

What 3 mechanisms increase venous return of blood to the heart?

> Skeletal muscle pump
> Respiratory pump
> Sympathetic Nervous System

Explain how sympathetic input to the veins would increase venous return of blood to the heart.

Sympathetic input causes vasoconstriction > pressure increases > drives blood through one-way valves back to the heart

Explain how the skeletal muscle pump would increase venous return of blood to the heart.

Veins pass between skeletal muscles.The contraction of skeletal muscle squeezes the vein > increasing blood pressure > Upstream valve (furthe...

Define: cardiac output, heart rate, stroke volume, end-diastolic-volume, ejection fraction.

>Cardiac output is the volume of blood pumped by the heart per minute (mL blood/min).
>Heart rate is the number of heart beats per minute....

If heart rate is 100 beats/min and stroke volume is 100 ml/beat, then what is the cardiac output?

Cardiac Output (mL/min) =
heart rate (beats/min) X stroke volume (mL/beat)
>10,000 mL/min

What factors cause an increase in stroke volume?

>Increase end-diastolic volume
>Greater ejection fraction

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4.2 Cardiac Output
TermDefinition

What 3 mechanisms increase venous return of blood to the heart?

> Skeletal muscle pump
> Respiratory pump
> Sympathetic Nervous System

Explain how sympathetic input to the veins would increase venous return of blood to the heart.

Sympathetic input causes vasoconstriction > pressure increases > drives blood through one-way valves back to the heart

Explain how the skeletal muscle pump would increase venous return of blood to the heart.

Veins pass between skeletal muscles.The contraction of skeletal muscle squeezes the vein > increasing blood pressure > Upstream valve (furthest from heart) closes > Downstream valve (closest to heart) to open.

Define: cardiac output, heart rate, stroke volume, end-diastolic-volume, ejection fraction.

>Cardiac output is the volume of blood pumped by the heart per minute (mL blood/min).
>Heart rate is the number of heart beats per minute.
>Stroke volume is the volume of blood pumped out of the left ventricle with each beat (mL/beat).
>End-Diastolic Volume is the volume of blood in the ventricles at the end of diastole
>Ejection Fraction is when ventricles eject their volume during systole.

If heart rate is 100 beats/min and stroke volume is 100 ml/beat, then what is the cardiac output?

Cardiac Output (mL/min) =
heart rate (beats/min) X stroke volume (mL/beat)
>10,000 mL/min

What factors cause an increase in stroke volume?

>Increase end-diastolic volume
>Greater ejection fraction

How does an increase in sympathetic input to the ventricular myocardium cause an increase in stroke volume?

Sympathetic input to ventricular myocardium > increases intracellular Ca2+ > stronger contraction > greater ejection fraction > increased stroke volume.

How does an increase in end-diastolic volume cause an increase in stroke volume?

Elevated venous return increases end-diastolic volume, which stretches the heart, optimizes the length/strength relationship of sarcomeres and thus increases stroke volume.

Describe Starling's Law.

Starling's Law describes the relationship between end-diastolic volume and stroke volume. It states that the heart will pump out whatever volume is delivered to it.

How would an increase in sympathetic input to the veins cause an increase in cardiac output?

Sympathetic input > vasoconstriction > increases pressure > increases venous return > increases end-diastolic volume > increases stroke volume > increases cardiac output

How would an increase in sympathetic input to the heart cause an increase in cardiac output?

1. Release of norepinephrine > increase in the strength of myocardial contraction > increases stroke volume.
2. Norepinephrine increases diffusion of Ca2+ into muscle fibers during action potential > increase in the ICF concentration of Ca2+ in myocardial cells > faster actin/myosin cross bridging (heart rate).
3. Induce release of epinephrine from adrenal medulla > Epinephrine stimulates an increase in strength of myocardial contraction > increase stroke volume.