Muscles, Part 1 - Muscle Cells: Crash Course Anatomy & Physiology #21

[@Kenstoes]

NEVER STOP DOING WHAT YOU ARE DOING. YOU ARE SAVING MY WHOLE EXISTENCE. THANK YOU THANK YOU

[@snugnuggz]

+Umesh Lawati fck u

[@GingeredHonii]

why suck violence, don't act like a *mitch* the word makes me laugh everytime XD KEVIN HART... DAMN YOU

[@Titanoboa3]

I agree! Great for visual learners! I wish there was a KZbin channel like this but for math!

[@kanaandistant4429]

KZbin cop! We are the LAW! There is

[@AimForTheBushes908]

Eventually he will have to stop since physical life is finite and like all of ours his will come to an end.

[@morganstevens5829]

VIDEO NOTES: MOVEMENT: 2 MAIN RULES 1. Proteins like to change shape when stuff binds to them 2. Changing shapes can allow proteins to bind or unbind with other things SARCOMERE: •contain 2 active proteins of actin and myosin •Thin actin strands and thick myosin strands •In a z shape, contract brings together •When muscles are resting, actin and myosin do not touch, but want to SLIDING FILAMENT MODEL: STEPS: 1. Actin wants to go to myosin but is trapped by tropomyosin and troponin 2. gaurds can move with ATP and calcium (sarcoplasmic reticulum loaded with calcium pumps) 3. eceptors on muscle cells release AcetylCoa and rush of sodium goes to cell, causing sodium channels to open in muscle cell 4. action potential goes to T-tubule 5. calcium stored inside t-tubule is released 6. troponin binds with calcium, causing the protein to change shape as it pulls trypomysoin away 7. ADP attaches to myosin and myosin goes into stretched position 8. myosin finally binds to actin and myosin releases stored energy and retracts whole muscle 9. ADP and phosphate unbind with myosin and ATP binds with myosin 10. myosin releases from actin 11. myosin then breaks down ATP to ADP and phosphate to get ready for next release of energy 12. calcium pumps grab calcium from tropomyosin back into place ~keeps replaying~ I hope some of these help you! If you are reading this, just know that you are such a beautiful, wonderful, and intelligent human being! I hope you all have a lovely day/night

[@rpkimble4568]

thank you so much for this. ive watched this video a few times. some of its sticking and some not. these notes are a gods send!

[@arthurpenndragon6434]

Doing the lord's work, thank you.

[@12345nidal]

Also for #5, calcium is released from the terminal cisternae of the SR, not the t-tubules.

[@morganyu3391]

Saviour.

[@S_K-rk7lo]

Thanks brother..made it more clear.

[@illblues1072]

The “chemistry” between myosin & actin makes my heart beat (:

[@gmianosi]

Watched these videos to study for the MCAT. Crushed the exam and got into my top choice medical school. Now I'm using them to study for med school exams. The story keeps repeating itself! You're the best, Hank!

[@lenyferabago2624]

Very good

[@simplymaci]

Dear Hank, Thank you for saving me when I have an Anatomy test the next day. Sincerely, Everyone Subscribed to CrashCourse

[@katiekeller952]

Literally me today!!

[@alexandriapahides4152]

Sammmmeee

[@amandavuono1992]

LOL I even listen to them on my 45 minute ride to class the day of my phys exams!! It really works

[@carlyewilson6600]

amen to this

[@jasmineintheclouds]

Me right now buddy ...me right now

[@monj5492]

That myosin head ain't loyal tho. Switching actin binding sites all the damn time

[@aroshkarodrigues1023]

Baller

[@Tremor244]

What's fascinating to me is just how quickly all this happens

[@miluska730]

one day I'll owe you my medical degreee

[@MemeRepublic]

milu ska did u get it yet?

[@kingos7643]

@@MemeRepublic too early to ask my guy 😂😂😂

[@TaliAlba33]

I'm just gonna comment here for me to get a notification from when she answers the question.

[@yarahamdan6657]

@@TaliAlba33 same

[@DeeBest]

Same

[@speedstacker51]

This stuff absolutely blows my mind. On another note, my professor basically spent two 50 minute class periods on the sliding filament model and I only had to watch this video twice to learn what I needed to know. You guys do great stuff, thank you!

[@randomcrazychic143]

Try a 2 hour and 10 minute long class...

[@sarthakparashar7508]

@angelswave88 Dude, all teachers are good guys here. They're trying to make us a little smarter. The Green brothers are absolutely awesome 👍😎. But that doesn't mean we need to demean our college profs 😇

[@sav2572]

angelswave88 well my high school anatomy teacher spent less than one 45 minute class on this soo

[@clairefolkert8771]

Thank you Hank! I hope you know that your biology and anatomy/physiology videos are educating future nurses (me), doctors, surgeons, exercise scientists, physical therapists, etc. just trying to fumble through the undergrad years of college!

[@ambercaitlin7364]

+body parts this is basically pre med made simple. At my school pre med is incorporated into our high school syllabus (for some reason our school system hates us all) since we pick our subjects according to what courses we want to take in Uni (the system makes no sense)

[@MJLionnavy]

Also, future dancers (me) and professional athletes. 'Cause we're expected to know our bodies in order to prevent the need for nurses, doctors and surgeons, and to make the physical therapists (which are kind of inevitable given that we're high performance athletes) job's easier.

[@deborahdavidson4035]

Hopefully a future Marine Biologist or two too :D

[@Sweetmotion23]

PE teachers too!

[@lucywaterman8905]

and vets!

[@lizardinabigwizardhat]

When you reference your own brother's bestselling novel

[@StarryNightt.]

@@kellyendicott4517 Yes lol. The Fault in Our Stars

[@brandoncraft1205]

I was looking for that comment, loved the nod to Hank lol

[@MessieXgirl3]

Love the fault in our stars reference

[@crashcourse]

Jess245 Fun behind-the-scenes fact: that was Nick's own on-set edit :D -Nicole

[@MessieXgirl3]

CrashCourse love it and love him! !

[@TENINCHLUVABOY]

CrashCourse When is part two coming out ?

[@TENINCHLUVABOY]

***** Thanks .

[@crashcourse]

PRICHARDxLUST GAMERxGIRLZ Next Monday! Barring anything unforeseen, new A&P episodes go up on Mondays at 3pm Mountain Time :D -Nicole

[@sonderingsong2000]

I lost it when he referred to his bro's book like, "Okay?" "Okay."

[@dennischiu272]

Do you even -lift- attach and release your actin and myosin, bro? :D

[@kiharapata]

Dennis Chiu wouldn't you have to leave it attached to be able to lift?

[@dennischiu272]

Guilherme Pata The act of lifting implies that of lowering. Hence the release. Repeat 4,500,000 times to become Arnold Schwarzenegger.

[@kiharapata]

good point

[@robinchesterfield42]

Nerd-bros. I love it. :)

[@melmedina9055]

Understanding science with a joke... Genius.

[@erinmcnally7764]

I am a 34 yo adult who has recently decided to go back to school to study Medical Coding and Billing/Health Services Administration and currently I am studying Medical Terminology. These videos have been so helpful I am am so grateful that you and all of your wonderful people have taken the time to do these videos because it really does help. Not just learning the term and definitions but also the explanation of the terms or at least some of them. Now, how do I get you to be my professor? Because in all honesty, you make it all fun. Thanks again!

[@ethanchang5428]

I love how Hank makes a reference to his brother's, John, book. "Okay? Okay".

[@brooklynnb7782]

OMG I DIDN'T KNOW lol

[@bhjgkuyjfyu]

omg john is his brother???

[@AnuRMusicVideos]

Yup John Green is his brother xD He does humanities videos on this channel while Hank does more science-y videos, plus he's on the channel Vlogbrothers along with Hank!

[@SMya-xk3jr]

Ikr, half fangirled. 🤷🏽‍♀️😍 Then got very serious again, cuz it's biology 😒.

[@ehabjaradat6580]

I can't beleive I'm smiling while studing Thank You !

[@chrisman212121]

same here !

[@luckystrke]

Our bodies are unbelievable.

[@Thumbsupurbum]

unbelievably small

[@gentlegoat6663]

Please don't mention god.

[@scientificninja7622]

Dr.Smarty Pants it's true but crash course gives an encouraging welcome to learning making you want to learn more, and they make it so relatable that it sticks to your head and I don't think you can become an MD without a strong learning attitude and a good retentive memory which I believe crash course gives the best foundation

[@JoseSanchez-bp7xz]

luckystrke Yeah, people walk around all the time letting out smelly farts. Some people love to whiff them because they like the smell of their own smelly farts.

[@Thomas_Winters]

(*sheds a tear*) beautiful...

[@umersaleem4148]

I was cоmpletely shocked bу how dramatic thе results wеre after just оne week. My energy levels were noticeablу higher aand I felt like аn absolute beast in the gуm.. => twitter.com/388c910fe281456e0/status/742668391975096320 Muscles рart 1 Musсle Cеlls Crash Course A P 21

[@Thomas_Winters]

Umer Saleem wot.

[@kathywhite2135]

i ship it

[@winningKQQ]

He makes all of his videos so colorful! Thank God he's not bland like the average A&P teacher!!! He makes it so much easier to understand verses just copying a bunch of powerpoints!

[@katherinehenry4729]

I am a 20 year old in college taking human physiology and i swear crashcouse never gets old 😂😂 i cannot tell you how much this channels helps with school!!

[@nobunuggets9088]

With background info from my textbook, the analogies you use and the animations really help me learn and understand each of these processes. I really thank you and your team for these videos. Without you, I’d be lost in my classes. I owe you a great deal when I finally become an RN!!!!!

[@izzypooley4683]

Favorite part: 9:00 "The whole drama plays itself over and over again, kind of like you'll have to replay this video over and over again to catch all the little steps." I had to laugh as I paused it for the 40+ time to take a note.

[@connorshipley168]

"The mitochondria is the powerhouse of the cell" -Said every biology book ever

[@jarchive4267]

Saliva contains Amylase, an enzyme that digests starch.

[@annad.1343]

Until you get to oxidation phosphorylation

[@bonesandhearts5683]

honestly I don't think I've ever heard the term "powerhouse" except when referring to mitochondria.

[@scientificninja7622]

myosin. .....guys actin...........girls tropomyosin.....father troponin. ........mother ATP n Calcium.............(varies)...time, grandparents, heart change, luck....etc 😁😁forgive me...just couldn't resist

[@angr5383]

scientific ninja 😂😂

[@fabybeltran1463]

scientific ninja thank you!!!!!!!!!!!

[@georgerekhviashvili7008]

ATP + calcium would be 💰 money.

[@ronnievillasenor4183]

Love this!!

[@iheartteresa]

yo this actually makes sense lmao thanks!!!

[@devonmerriman5874]

Actin and myosin...sounds like "action and motion". Fitting.

[@CzechRiot]

You look a bit like Rachel Evan Wood in this small picture

[@MuhammadFaisal-hc9nt]

still better love story than twilight

[@lironkoren2394]

Muhammad Faisal BAHAHAAHAHA

[@vbbt21]

Well could have been if the guy would have been R Patz

[@cammandokittie]

Lmao STOOOOP

[@ash_sen844]

I would think itachi would like twilight

[@klutz3955]

haha, never change internet. never change

[@lizflores6994]

He was right about repeating this video over and over. Just to take notes and understand the whole very complex concept. . I dislike reading just read this whole chapter and understood absolutely nothing...but Learned more in this crash course.

[@jackiebazan7459]

Literally learned more just in this one video then I have this entire semester in Anatomy.

[@victoriabledsoe6422]

I love how he mentioned watching it multiple times. I totally paused and rewatched sections, as well as watched it in half speed. Definitely provides a basis for my classes so I can begin to understand!

[@initialsCKN]

HANK, I DON'T NEED TO START HAVING FEELS ABOUT MY MUSCLES EVERY TIME I MOVE.

[@shourishmukherjee1510]

And when you run a mile....

[@shaki6500]

troponin : girl's mother tropomyosin: girl's father Ca+2: flowers Actin: girl Myosin: boy when the boy buy flowers for girl's mother, she pushed her husband out of the away , and romance begin !

[@whitneystevenson8355]

He ideally isn't someone I'd choose to hang out with on a Friday night but I find that as I take A&P, he's the only person I end up hanging out with on a Friday night. If you can get past his dorky sense of humor and ignore some of the extras, you can really get a lot out of this for A&P. I'm completely new to this class and never even thought of going in this direction that I'll be majoring in so this class has been hell, to say the least. But the way he breaks it down is perfect. The animations really are a huge help because they're broken down into kindergarten terms. Highly suggest him. He definitely gains my respect. I don't normally post comments but I figured he doesn't get near as much credit as he should for all the help he's given over the years. Appreciate it!

[@TheEmilyAnn100]

I have an anatomy exam on this and some other stuff tomorrow... this just saved me a solid 2 hours of studying. Thanks so much!!

[@floweringtowers]

When chemistry was introduced to my A&P, my heart literally sank I was TERRIFIED. I have a wonderful professor, but I probably kept rereading my textbook chapters like 20 times and it was still not making ANY sense. Legitimately I have never been more grateful to find a channel that is helping me at the very least pass!!

[@RM1Sammy]

Took honors A&P during High School and it was one of my favorite classes ever. The human body is so interesting and the amount of detail to it is just endless.

[@BinalPatel28]

You knew we would rewatch and replay LOL! That made me laugh!

[@DeeBest]

Me too

[@klutz3955]

haha i didn't but i think i will anyway. :P

[@Iceabella]

Eating, texting, taking notes. Repeating segments of the video a hundred times. You really know everything, Hank!

[@valentinabarrosclark8472]

Im 1 year at PT school, and I subscribe to Crash Course and its saving my life. this week I passed my first exam about research in health with 8 (scale 1-10) THANK YOU regards, a future physical therapist

[@Sandorfitness]

Hank and John Green. The modern day Bill Nye Show. Love it!

[@nicoperezgalli984]

I wish I could give this guy a thousand likes, my house, my glycogen reserves, some of my myosin and all of my ATP. This has got to be one of the best channels on KZbin!!! Thank you so much!

[@ChristieNel]

Who needs school when you have CrashCourse?

[@sjwimmel]

Christie Nel Well....I agree with the sentiment, but really, everyone needs school. This is great content, but it can never be a replacement for a teacher who's actually in the room with you. How about a school where the homework is watching Crash Course!

[@spazmaster1996]

J. van der Linden i'd say everone needs education, as education leads to growth of the mind and the continued greatness of our species... however school is different to education, if anything its more like an evolutionary cousin. School is merely societies way of measuring your worth by filling your brain with facts, for you to regurgitate during an exam. There are many forms of education for example crash course :D education is needed, school is in need of education. Also crash course as homework would be awesome

[@135794415]

GUYS......he's joking.......

[@000selma]

Christie Nel These videos are really nice!

[@KMM496]

+Liam Worsley chill nobody cares

[@Jennifer-zb4dq]

I couldn't do this without you. I might actually pass this exam tomorrow 😅

[@pink11514]

Literally, you’re my favorite person on the internet. I love listening to you talk, your analogies help this class make so much more sense, you’re funny and for once, science isn’t boring to listen to!!! Thank you Hank Green!

[@edwardmaximus5439]

For the love of god! Please keep these videos on KZbin until the end of time! You’re a life saver

[@Barnardrab]

Watch this video again? I'll be watching this whole series again.

[@cesararellano5528]

bro this man made me understand all of this in literally 10 minutes, THANK YOU I WILL CONTINUE MY NOTES and actually understand what I am taking notes of.

[@1234kalmar]

No wonder evolution took hundreds of millions of years to get to multicellular organism. This is fascinating!

[@Wiiman915]

But they did have to have the ability to reproduce/duplicate with the very first thing we could call life.

[@1234kalmar]

Ray Sharky I just knew relgious nutjobs would appear sooner or later... Well, better go ahead of the useless flamewar...

[@Yeahdominic]

+Robbie Jeffcott yes they did. reading might actually help on your question

[@1234kalmar]

shena mackey There is too much evidence to the contrary.

[@ArcParadoxPlays]

+1234kalmar not enough

[@giannaj9397]

I’m here studying for STEP 1 and I forgot how much I loved you during MCAT studying!! Truly the GOAT

[@Jeudaos]

9:09 YUP, called it. I had to skip back about a dozen times to get ALL of the information I needed about the Sliding Filament Model, and the actin and myosin.

[@valroe7034]

THANK YOU SOOOOO MUCH TO THE WRITERS AND PRODUCERS OF THIS SERIES. Truly a godsend.

[@1247peace]

why cant my teacher be this fun

[@michaelak6753]

they dont get paid nearly enough to prepare fun animations and pop-up notes to go with their lecture lol

[@NarutoSSj6]

Bcuz your not trump

[@dmitrydyachenko4301]

well, your teacher is telling the same thing over and over that much, that he/she is doing it automaticly, without thinking whether it is fun or not. His/jers aim is to make you understand in the way you could further show that on test and enter the university w/this knowledge.

[@graciegonzales2077]

My teacher sometimes show videos like this whenever he doesn't feel like lecturing our class himself. I was able to repeat these videos as well. I also use my notes and encyclopedias to help me learn more about anatomy.

[@graciegonzales2077]

Yes. I still have encyclopedias at my house.

[@Abominatrix650]

The perfect channel for anyone studying A&P!

[@rodriguezgeorge8364]

I really enjoy these videos they reinforce my understanding of my lectures. Thank you.

[@allidurdin]

These videos are saving my life!! 96% in Human Biology !! Never stop these !!

[@Danilego]

This is so awesome and interesting, I’ve always wanted to know how our bodies ACTUALLY work and move on the cellular level and you guys teach us with so much detail! Thanks Crash Course

[@LelouchSaya]

I'm a German medical Student and love these videos to get an unterstandable and entertaining introduction to my topics!

[@EliteMaStEr7]

Anyone else lookin' at your muscles and thinkin' 'holy shit' :O ?

[@ellis1034]

I just want to say that this channel is the sole reason I passed my histology exam because my lecturer is useless and my textbook was way complicated. So thank you for breaking it down and helping me visualize YOU ARE MY HERO NEVER STOP WHAT YOU'RE DOING

[@prutsemie99]

This not only explained everything I wanted/needed to know, it was also super fun to watch and the references to the daily life/love story really do make it easier to understand. Thank you for saving both my grades and my brain from a breakdown.

[@medschoolpowerpoints6574]

I watched this years ago in high school, I watched it again in medschool and now preparing for usmle I'm watching it again. Crash course is one of the best resources I've ever seen. 👍💯💯 💯

[@VenseyNess]

When I booted up this video, I watched it for about two minutes, before this dialogue went through my head: "Wait, how do my muscles contract anyway? It probably has something to do with being activated by synaptic charges, as with all things. But why can my brain make synaptic charges?" It was at this point that I paused the video because I needed a minute, continuing: "What makes a brain able to crate electric charges form its desire. And to that extent what makes me a person, and not just a brain. I mean, I'm like a space probe. My eyes are the camera, my mouth the analysis lab, my digestive system my solar cells and my heart my power distribution system, but spacer probes are controlled by people, what am I controlled by? A brain? Well obviously but I mean, what else. And for that matter how weird is it that I'm technically a brain whose thinking about its body thinking about its brain which is now thinking about its body. When did that happen, like, in an evolutionary sense? When was it possible for something to think about itself like that. Has anything but a human done it?" Followed by about 30 minutes of rambling. Also, if you read all that... wow, you're a trooper. Thank you? I guess?

[@chillsahoy2640]

Vensey Ness After reading this, all I can think of is one of the verse's from Hank's song /The Universe Is Weird/, "The Universe created a tool with which to know itself." So you are a construct made by the Universe (through a rather slow process of star and planet formation, then formation of life and finally billions of years of evolution) which it uses to understand just how weird it is. Admittedly, some artistic license is required to think of the universe as a being with agency and a will.

[@adrianaleone3382]

Vensey Ness and I am thinking about you thinking about your brain thinking about your body... through a comment in other language written in a video on the internet

[@kevinconnelly6770]

Vensey Ness na, i just skipped to the end, i aint not no trooper

[@LordOfTheObvious]

Vensey Nessit makes so happo to see people think like that.

[@lioneldamtew9533]

E Hernandez it's actually a quote from Carl Sagan: "Some part of our being knows this is where we came from. We long to return. And we can. Because the cosmos is also within us. We're made of star-stuff. We are a way for the cosmos to know itself." -Carl Sagan

[@kylandry7205]

i loved watching hank's crash courses in highschool. i now find myself here again helping me through my first semester of college.

[@crashcourse]

Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App! Download it here for Apple Devices: apple.co/3d4eyZo Download it here for Android Devices: bit.ly/2SrDulJ

[@redflameyt7984]

great!

[@eminem420redsox]

Not available for droid phone's:(

[@veronicayousif667]

THANK YOU!!!!! The text book was not making any of this clear. Now I actually get what's happening. You are my savior!!!!

[@isisrendon3805]

I did re-watch this video, again and again and again. It's just such a great love story.

[@parhamizady8616]

Sliding Filament Model: 1. Brain sends an action potential to the motor neuron until it synapses with a muscle cell in the arm by releasing acetylcholine 2. Receptors on the muscle cells open up and release a rush of sodium into the cells as a graded potential (since they are ligand-gated sodium channels) a. If strong enough, nearby voltage-gated sodium channels open 3. Action potential goes to the sarcolemma’s T-Tubules, and triggers voltage-sensitive proteins linked to calcium channels in the sarcoplasmic reticulum 4, Calcium channels are opened and release a rush of calcium into the cell 5. Calcium binds to troponin and changes shape, then pulls tropomyosin away from actin strands that myosin wants to reach 6. Myosin that contain and converted ATP to ADP move into a stretched position and bind to actin 7. Myosin releases its stored energy and changes shape by pulling on actin strands 8. Sarcomere retracts and causes the muscle to contract 9. Myosin unbinds with ADP and phosphate and changes shape, which causes ATP to bind to the myosin 10. Myosin changes shape and unbinds from actin 11. Myosin converts new ATP into ADP and phosphate to be prepared for the next release of energy 12. Calcium pumps take calcium from tropomyosin to restock sarcoplasmic reticulum 13. Tropomyosin is put back into place

[@ajarofpickles2826]

Whoever came up with muscles is a genius thanks god!

[@latishanaomi7618]

Read my chapters on sliding filaments for two days and couldn’t understand. Then learned it in 30 mins of watching this video while taking notes and screenshots. AMAZING!

[@forpeanutjelly4323]

It takes guts to learn Anatomy

[@horror_and_legos]

Crash Course is my hero. I have used them for both US History and Human A&P and they never let me down!

[@wcbpolish]

Just realized that at: 7:05 he references his brother's book "Fault of our stars" which I am currently reading.

[@GuitarGrrrella]

Can't thank you enough! You are a brilliant teacher! I've taken a lot of classes online and most of them aren't taught very well. I hope you keep getting donations so you can keep offering these classes for free. You're the best online teacher I've seen. Heck, you could probably create an online course on udemy or somewhere teaching people how to teach an online course. You could probably charge $100 for it... But please keep offering these classes for free. They're a lifesaver for some of us.

[@thecat944]

Thank you Hank. Your videos are so helpful! You should know many of us (including myself) are going into the medical field, and we could not be more thankful!

[@meredithwharton4040]

Why can't everyone make science fun like you! THANK YOU!!!

[@AndresWamonde]

definitely one of your best videos yet guys, great work

[@Missydizzychick1]

Thank god, my lecturer has called in a student to teach us this section and she makes absolutely NO sense. These videos are saving my grade!!

[@kathleendonlinger7023]

Thank you so much for creating these videos, I wouldn't have passed any of my science courses without Crash Course!

[@patrickmeehan6856]

Pure brilliance. Shakespeare and the sliding filament model. Cross curricular education at its finest!

[@audreyleeann6843]

The accuracy how he said I was eating and texting and taking notes and Im definetly going to have to rewatch this 🤣

[@NicolineNDahl]

I'm freaking slightly out. I study physiotherapy. The 20th august I have my 3rd attempt to pass my physiology exam, and in Denmark you HAVE to pass on your third try. I fly to Portugal for a three month college internship the 21st and if I don't pass, my whole undergrad is laying dead on the floor. I am so SO grateful for crash course! If anybody reads this, please send me positive thoughts. Thank you for helping me save my butt Hank :)

[@user-hz7pk9vb6z]

I wishing you the best.

[@dreamkiller189]

suggestion: circulatory system & respiratory system please :)

[@crashcourse]

dreamkiller189 Patience, friend! This course hasn't even reached it's halfway point yet. We've got a lot more A&P to cover :D -Nicole

[@sixsunss8032]

+CrashCourse A&P is such a big course.. even in my tense master study(2 -3 big chapters per week) we still have to spend around 6 months to generally cover all aspects, not in detail...Now it is just my first 2 months, I hope this crush courses can be accomplished within 4 months too! Those animations are sooo cute!! I love to watch them over and over again.

[@katarzyna6898]

+CrashCourse Hi CrashCourse. May we request a hardcopy of the Anatomy and Physiology lectures? Thank you!

[@janellejcj10]

I had to take notes step by step to get the process and now I completely get the concept! It was one ear and out the other in my lecture but now since watching this video for 2 hours, i get it now. I should be prepared for my exam this Wednesday.

[@sebstoner1]

This video is better than anything my biology teacher says...

[@merandabubbles1124]

Your enthusiasm for muscles reminds me why I became a massage therapist. Thank you for this vid.

[@ImJustMe747]

Seriously, seriously SERIOUSLY great video. I'll be looking for more

[@jinx7501]

We've been studying this for a few weeks, I have tried but failed to comprehend it. We're talking hours of lectures here, me curled up in the corner in the fetal position trying to understand it all.... watching this video and ohmergoodness... thank you

[@bintzubair]

THAAAANNKKKSS I WAS SO HAPPY WHEN I TYPED IN MECHANISM OF MUSCLE CONTRACTION AND FOUND A CRASH COURSE VIDEO ON IT I WAS LIKE YAAASS IM GONNA GET IT ALL INTO MY HEAD. NOW MAKING THE PRESENTATION IS SO MUCH EASIER

[@xnabr7603]

Crashcourse, on behalf of all the academic viewers so passionate about learning and those viewers who procrastinate in school, thank you.

[@jaimeshirey2263]

you're the reason I'm passing my tests just so you know! thank you for creating this channel its saving my life (∩_∩)

[@erikasandoval5614]

I swear if I had him as my professor for Bio I wouldn't mind going to class. Thank you for explaining this part of the chapter in a way we can understand it. you are helping me for my bio exam. BLESS YOUR SOUL

[@meows_and_woof]

“ they don’t touch but really really want to” Sounds like my sad love life

[@StoneyJG16]

Already had an idea of how myosin heads grab onto the actin molecules, but it totally helps watching the animation and actually seeing it rather than looking at my A&P book! Crash course is always a savior

[@TheMrzippie]

Just noticed the anglerfish plushy. I won't be sad while watching this ever!

[@aphrog649]

They call it a "Hanklerfish". I think they might even have Hanklerfish merch lol.

[@KatesCooking]

I love when my anatomy teacher shows us crash course videos! It helps me understand so much better.

[@rsek941]

This video is going to save my Anatomy grade..

[@sullysidedown1253]

Loving that these videos are included on my diploma in Australia. I would not be passing if these videos didn't exist.

[@izlinaameera113]

AND THIS LOVE STORY MY FRIEND, IS THE MOST BEAUTIFUL LOVE STORY EVER EXISTED

[@Haylortatch29_]

SO much of me wants the little noise that happens when the ions bind to receptors/troponin as my message tone. Its so satisfying and also reminds me of how much these videos are going to help me nail my exams!