Preload and Afterload

Why Doesn't the Heart Rip?

Understand LaPlace's law to see the effect that pressure, radius, and wall thickness each have on the "wall stress" in the left ventricle. Rishi is a pediatric infectious disease physician and works at Khan Academy.

What is Preload?

Some say Preload = End-Diastolic Pressure, others say Preload = End-Diastolic Volume, so which one is it? Watch and find out! Rishi is a pediatric infectious disease physician and works at Khan Academy.

Preload and Pressure

Find out how left ventricular end-diastolic pressure helps you make an educated guess about preload. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Preload Stretches out the Heart Cells

Find out why stretching a heart cell in diastole affects how forcefully it contracts in systole. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Frank-Starling Mechanism

Carefully follow 5 different preload scenarios to see how each one will have a different effect on how actin and myosin line up. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Sarcomere length-tension relationship

Find out why the length of a sarcomere (in diastole) affects the amount of force that it can generate (in systole), and how that would look on a graph. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Active contraction vs. passive recoil

Go through the similarities and differences between the sarcomere and a slingshot! Rishi is a pediatric infectious disease physician and works at Khan Academy.

What is afterload?

Rishi is a pediatric infectious disease physician and works at Khan Academy.

Increasing the Heart's Force of Contraction

Find out exactly how stretch increases force of contraction in end-diastole, whereas more calcium increased force of contraction in end-systole. Rishi is a pediatric infectious disease physician and works at Khan Academy.