Muscles, Part 2 - Organismal Level: Crash Course Anatomy & Physiology #22

Hank calls in a friend to do his push-ups for him today to explain how skeletal muscles work together to create and reverse movements. Hank and Claire also demonstrate the role size plays in motor units, the three-phase cycle of muscle twitches, and how the strength and frequency of an impulse affect the strength and duration of a contraction. This episode also explains twitch summation, tetanus, and isotonic vs. isometric movements.

Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App!

Chapters:
Introduction: Heavy Lifting 00:00
How Muscles Push & Pull 1:13
Functional Muscle Groups: Prime Movers, Antagonists, and Synergists 2:27
Motor Units 3:49
3 Phases of Muscle Twitches: Latent, Contraction, Relaxation 4:41
Graded Muscle Responses 5:22
Temporal Summation vs Tetanus 6:19
Multiple Motor Unit Summation (Recruitment) 7:07
The Size Principle of Recruitment 7:52
Isotonic vs Isometric Movements 8:50
Review 9:28
Credits 9:59

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TO: Ariela
FROM: Gavi

I love you so much, stay awesome as always!

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TO: Josiah P.
FROM: Amy P.

I love you!

***SUPPORTER THANK YOU!***

Thank you so much to all of our awesome supporters for their contributions to help make Crash Course possible and freely available for everyone forever:

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Want to find Crash Course elsewhere on the internet?

[DenellaGaona]

I REALLY do not know how I'd get through nursing school without you guys thank you!!!!

[AndreaGonzalez-gqjo]

i’m a medical student and i gotta say, these videos are pure gold, i watch them to give me a brief summary of what we just saw, and I was seriously impressed by how much detail there is in these. Thanks Hank

[annelmoreno]

THANK YOU HANK AND CRASHCOURSE TEAM FOR EVERYTHING YOU DO FOR US STRUGGLING STUDENTS. YOU HELPED ME UNDERSTAND 4 LECTURES WORTH OF INFORMATION IN JUST 20 MINUTES (I watched 2 crashcourse videos on muscles) I AM FOREVER GRATEFUL 😭😭😭😭🙌🏼🙌🏼🙌🏼

[corisvibing]

When my science teacher explains it she is so serious and she doesn't make it fun but he makes it easy and fun for me to learn it and for me to actually pay attention because science is my favorite subject.

[davidsalinas]

I'm in human anatomy right now. And man. Because of you. I changed my grade from a D to a B+ bro YOU ARE THE

[Abominatrix]

Shoutout to Claire and the corgi! Thank you for helping us all learn!

[coryrice]

Hello CrashCorse! A friend of mine recently recommended your channel since I teach anatomy and physiology labs and he felt your videos might be beneficial to my students. I must admit, I'm impressed. I was expecting grossly over-simplified explanations with borderline inaccurate information which would be misleading and/or confusing, however your presentations are simple, accurate, and engaging. I really like what you all have done! During my labs I like to imagine that I have the energy and charisma that Hank does, but in reality I probably more closely resemble Ben Stein from Ferris Bueller's Day Off... Anyway, I digress.
Minus a few tidbits here and there, your videos touch on much of the information I present prior to carrying out lab exercises. I have enjoyed your videos and would like to post links to some of your content as supplemental material for my students. If this is possible let me know. Thanks!

[RunninAD]

"The stapedius in your middle ear, which I've been doing my best to workout lately, but I just can't get any tone."

C'mon Hank, you're better than this, how could you miss that pun.

[gracebrewer]

I use these videos to preview and then review each subject. They are so incredibly helpful!

[bernardoguerrero]

I just binged all the videos in this series to review for my exam today

[vrstovsek]

I love this guy! He just puts smile on my face :)

[crashcourse]

Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App!

[jonathancook]

"how can Claire gently pet this can at one moment and then quickly crush a corgi in another?"

[genanhamideh]

this episode made my brain blow up and me cry

[gmfPimp]

These videos are very well done. The amount of information presented in such a short amount of time would normally be overwhelming. The approach used works very well.

[leannecameron]

Thanks CC, so fascinating! Would love to see your explanation on how a muscle gets stronger and bigger.

[RogerRoids]

That shaking molecule is bothering the hell out of me.

[Backcornerboys]

Ideas for another video: Why do muscles get stronger with repeated use? How do hormones affect muscle development? How does adrenaline affect your ability to contract a muscle against greater tension or with less rest? What happens when you pull/tear a muscle?

[zarkahameed]

Your videos just make things very clear and even more easy without confusing the audience..

[MsDafiM]

Yay Claire! What a lovely and very appropriate surprise it is to see you on an episode about muscles! :)