Hank tells us the story of the complicated chemical dance that allows our skeletal muscles to contract and relax.

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Table of Contents
1) Cardiac, Smooth, & Skeletal Muscles 01:09
2) Muscle Anatomy 02:03
a) Muscle Fibers 03:07
b) Myofibrils 04:15:1
c) Sarcomeres 04:19:1
d) Myofilaments 04:37:2
3) Biolography 05:37:1
4) Sliding Filament Model 07:47

References for this episode can be found in the Google document here:

crash course, crashcourse, biology, muscular system, muscle, cellular respiration, energy, ATP, human body, chemistry, cardiac muscle, smooth muscle, skeletal muscle, contract, relax, tendon, anatomy, physiology, fascicle, fibers, protein, myofibril, sarcomere, myofilament, actin, myosin, sliding filament model, biolography, electron microscope, tropomyosin, troponin, sarcoplasmic reticulum, motor neuron Support CrashCourse on Subbable:


  1. Thank you so much for this awesome episode!!! And the result that I got was also fantastic! The first time I got 100% in my Biology assessment!!! Thanks again for crash course!!! Keep on doing it!!!

  2. You have no idea how appreciative I am of this channel. It's helped me go through A&P, Microbio, Bio l and now finally…bio ll ? you guys are a godsend

  3. The knowledge was known, centuries before the Huxley family. We've been told so many lies. "Brave New World: Revisited." Is becoming a reality.

  4. hmmmm this rwminded me of hydoulics so i had an idea of doing some research on making a muscle substitute…then i though of boilagy but the cells would die out then i got the idea of tampering with those cells that keep your cells alive…..then zombie apocalypse came into my head…..i said nope and gave up on that on the spot….oh amd im 13

  5. I have been struggling to understand this for over a week, and you managed to explain it clearly in 12 minutes. Well done. Very well done.