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Heart Muscle Contraction

7 videos
Your heart is made of a special type of muscle, found nowhere else in the body! This unique muscle is specialized to perform the repetitive task of pumping your blood throughout your body, from the day you’re born to the day you die. We’ll take an in-depth look of how the heart accomplishes this on a cellular level, and learn about the proteins actin and myosin that are the workhorses that tug and pull on one another to create every single muscle contraction. You’ll appreciate the fact that your heart beat is a fairly sophisticated process!

Three types of muscle

VIDEO 11:29 minutes
Understanding the structure of a muscle cell.

Heart cells up close!

VIDEO 14:00 minutes
Get a close-up view of the cardiac cells and see what makes them different from the other (skeletal and smooth) muscle cells. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Myosin and actin

VIDEO 9:38 minutes
How myosin and actin interact to produce mechanical force.

Tropomyosin and troponin and their role in regulating muscle contraction

VIDEO 9:22 minutes
Tropomyosin and troponin and their role in regulating muscle contraction. How calcium ion concentration dictates whether a muscle is contracting or not.

Calcium puts myosin to work

VIDEO 10:03 minutes
See exactly how Calcium binds Troponin-C and allows Myosin to do some work.

Sympathetic nerves affect myosin activity

VIDEO 12:02 minutes
Check out how the amount of Myosin that is tugging on your heart can change depending on your activity level! Rishi is a pediatric infectious disease physician and works at Khan Academy.

Why doesn't the heart rip?

VIDEO 10:26 minutes
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.