Skeletal Muscle 2- Myofibers

Skeletal Muscle 2- Myofibers


– MUSCLE CELLS. THIS IS MY BROTHER,
RIGHT THERE, JUMPING OVER THE HEAD
OF HIS BRIDE ON HIS WEDDING DAY. MY BROTHER’S MUSCLES ARE
EXTRAORDINARY. AND WE’RE GONNA LOOK
AT THE CHARACTERISTICS OF THE MUSCLE CELL THAT ACTUALLY
ENABLE THIS INCREDIBLE FUNCTION. I MEAN SERIOUSLY. THE THING THAT HE WAS WORRIED
ABOUT ON THIS DAY WAS, HE DIDN’T WANT HIS PANTS TO RIP.
THAT’S AWESOME. I’M GLAD THAT HE WAS A LITTLE
CONCERNED ABOUT THAT. THIS IS VISUAL OF AN ACTUAL– A FULL MUSCLE ORGAN. WE’RE GONNA BACK UP
AT SOME POINT IN THIS LECTURE AND REMIND OURSELVES OF
WHAT A MUSCLE ORGAN IS. BUT I WANT YOU TO TAKE
A LOOK AT THE LEVEL OF ORGANIZATION
THAT WE’RE GONNA EXAMINE RIGHT NOW AND THIS RIGHT
HERE IS MUSCLE CELL. MUSCLE CELLS ARE WEIRD. THEY DEFINITELY ARE
UNLIKE ANYTHING ELSE. SO WHAT I’M DOING IS I’M ZOOMING
IN TO A LITTLE SECTION OF MUSCLE CELL AND THEN
I’M GONNA TELL YOU– THIS IS MY IMAGE. SO WE CAN COME BACK
TO THAT THING. I’M GONNA TELL YOU
SOME CHARACTERISTICS OF MUSCLE CELLS THAT ARE
DIFFERENT THAN OTHER CELLS. FIRST OF ALL, LET’S SEE. MUSCLE CELLS– SKELETAL MUSCLE CELLS HAVE
MULTIPLE NUCLEI. SERIOUSLY. HOW COOL IS THAT? AND THAT’S ACTUALLY BECAUSE WHEN
THEY WERE BABY MUSCLE CELLS, THEY DECIDED, DUDE, WHO WANTS TO LIVE IN YOUR
OWN HOUSE BY YOURSELF. LET’S ALL FUSE TOGETHER,
LITTLE BABY CELLS, AND ALL LIVE IN THE SAME HOUSE. AND THEY KEPT ALL THEIR NUCLEI.
BRILLIANT. MUSCLE CELLS CAN
BE EXTREMELY LONG. SO IT’S OF NICE THAT THEY
ALL DECIDED TO WORK TOGETHER AND MAKE ONE CELL. MUSCLE CELLS– SKELETAL MUSCLE CELLS HAVE TONS
OF MITOCHONDRIA. WHY? MITOCHONDRIA MAKE YOUR ATP
AND SO YOU NEED LOTS TO FUNCTION TO HAVE
YOUR MUSCLE CELL CONTRACT. YOU HAVE AN INTUITIVE
SENSE THAT YEAH, IT TAKES ENERGY
TO CONTRACT MUSCLE CELLS. SO WE GOTTA HAVE MITOCHONDRIA
IN ORDER TO FUEL THAT PROCESS. AND THEN THIS IS ANOTHER REALLY
INTERESTING– WELL OKAY. THOSE ARE CHARACTERISTICS THAT ARE LIKE NORMAL CELL
CHARACTERISTICS THAT ARE WEIRD. YOU TOTALLY UNDERSTOOD
WHAT I JUST SAID DIDN’T YOU? IN ADDITION TO HAVING SOME
INTERESTING CHARACTERISTICS, THEY ALSO HAVE UNIQUE NAMES. SO HERE’S– HERE’S SOME NAMES WE’RE GONNA
REFER TO. FIRST OF ALL, YOU’RE GONNA
HAVE THE SARCOLEMMA. THAT’S THE CELL MEMBRANE. IT HAS A PHOSPHOLIPID BILAYER PLUS SOME EXTRA STUFF
THAT MAKES THE SARCOLEMMA. SO IT ISN’T– IT IS A DIFFERENT
STRUCTURE THAN JUST OUR TRADITIONAL CELL MEMBRANE. THAT EXTRA STUFF IS– PLAYS ROLE THE NEUROMUSCULAR
JUNCTION WHICH IS THAT PLACE WHERE THE MOTOR END PLATE– WHERE THE SOMATIC MOTOR NEURON
DUMPS THE ACETYLCHOLINE. SO WE HAVE THE SARCOLEMMA. YOU HAVE SARCOPLASM.
WHAT DO YOU THINK THAT IS? THAT’S JUST CYTOPLASM
IN A MUSCLE CELL. YOU ALSO HAVE THE SARCOPLASMIC
RETICULUM. WHAT?
WHO’S THIS RELATED TO? THIS IS RELATED TO THE SMOOTH
ENDOPLASMIC RETICULUM. AND YOU’RE LIKE, DUDE,
I GOT THIS. SMOOTH ENDOPLASMIC RETICULUM.
OF COURSE, THAT’S THE CRAZY FOLDED CELL
MEMBRANE LABYRINTH THAT’S SMOOTH AND NOT COLORED WITH RIBOSOMES
THAT’S FOUND INSIDE MOST CELLS. AND I’M TELLING YOU RIGHT NOW. THE SARCOPLASMIC RETICULUM IN
THE MUSCLE CELL IS LIKE CRAZY. IT– I’M GONNA SHOW IT TO YOU BECAUSE IT’S
A SIGNIFICANTLY WEIRD THING. AND THEN I’LL TELL YOU ABOUT
SOME OTHER CHARACTERISTICS. THERE’S SOMETHING VERY WEIRD
THAT ISN’T FOUND IN OTHER CELLS. NUCLEI ARE FOUND IN OTHER CELLS. MITOCHONDRIA ARE
FOUND IN OTHER CELLS. THESE THINGS ARE
ALL FOUND IN OTHER CELLS. OKAY, COOL.
THEY JUST HAVE DIFFERENT NAMES. BUT YOU HAVE SOMETHING CALLED
A MYOFIBRIL AND THIS IS A PACKAGE
LIKE A BUNDLE. A BUNDLE OF
CONTRACTILE PROTEINS. AND THIS IS– THEY’RE ACTUALLY
LIKE CYTOSKELETON. THAT SAYS CYTOSKELETON. OF COURSE, IT DOES. SO MYOFIBRILS– AND I’M
GONNA SHOW THEM TO YOU. OKAY. LET’S GO BACK
AND LOOK AT OUR PICTURE. THIS IS ONE
SKELETAL MUSCLE CELL. THIS IS A MYOFIBRIL.
AND IT’S– IT CONTAINS THESE CONTRACTILE
PROTEINS. AND LOOK AT HOW THERE’S
LITTLE BUNDLES OF MYOFIBRILS ALL AROUND. LIKE ALL OVER INSIDE THE CELL
ITSELF. YOU MIGHT THINK OF IT LIKE– WELL, I THINK OF THEM
LIKE SPAGHETTI NOODLES. AND IT’S LIKE HAVING A PACKAGE
OF SPAGHETTI NOODLES. I COULD ACTUALLY PUT– THIS MAKES ME WONNA MAKE THIS. I COULD TAKE A BALLOON AND
FILL IT WITH SPAGHETTI NOODLES. AND DO YOU AGREE THAT I COULD
TOTALLY STILL POUR WATER IN? AND THAT’S MY SARCOPLASM. THAT’S THE CYTOPLASM. AND IT’S JUST GONNA SURROUND
THOSE SPAGHETTI NOODLES CAUSE THERE’S GONNA BE SOME PLACE
IN THERE. OKAY. HERE’S SOME OTHER INTERESTING
AND WEIRD THINGS. THE NUCLEI OF SKELETAL
MUSCLE CELLS ARE SQUISHED TO THE OUTSIDE BECAUSE OF
ALL OF THESE MYOFIBRILS. YOU CAN SEE MY MANY
MITOCHONDRIA HERE. AND GUESS WHAT THIS IS? THESE LIKE NET
LOOKING WRAPPERS AROUND– IT’S LIKE THEY’RE WEARING
THESE COOL DRESSES. EACH MYOFIBRIL IS WEARING
A DRESS THAT HAS HOLES IN IT. THAT’S THE SARCOPLASMIC
RETICULUM. AND IT HAS A VERY
IMPORTANT FUNCTION WHEN IT COMES
TO MUSCLE CONTRACTION AND STIMULATING
THE MUSCLE CONTRACTION. YOU ALSO HAVE THESE THINGS,
T-TUBULES. T-TUBULES ARE LIKE PLACES
WHERE CELL MEMBRANE– IT’S LIKE YOU TAKE THE CELL– YOU TAKE YOU BALLOON AND THEN
YOU POCK YOUR FINGER THROUGH IT. AND THE CELL MEMBRANE
INVIGILATES WHERE YOUR FINGER GOES AND POCKS DOWN INSIDE. AND T-TUBULES ARE
LIKE THESE LITTLE WHOLE. THESE LITTLE TUNNELS THAT ARE BASICALLY
MADE UP OF THE SARCOLEMMA, THE CELL MEMBRANE ITSELF. BUT THEY GO DOWN AND THEY
COME VERY CLOSE AND CONNECTED. LOOK THEY’RE VERY CLOSE AND CONNECTED
WITH THE SARCOPLASMIC RETICULUM. THAT’S IMPORTANT TOO. WHAT ELSE?
OKAY. THESE GUYS ARE ALL GONNA
COME INTO PLAY. NOW. ARE YOU CURIOUS
ABOUT THE MYOFIBRIL? YOU PROBABLY SHOULD BE AND
WE’RE GONNA BREAK THE MYOFIBRIL DOWN INTO IT’S FILAMENTS
THAT IT’S MADE OUT OF. IT’S MADE OF THICK FILAMENTS
AND THIN FILAMENTS. AND THEY’RE ORGANIZED
IN A CERTAIN WAY. AND WHEN YOU GET
A BUNDLE OF THICK AND THIN FILAMENTS,
THAT’S A MYOFIBRIL.

10 thoughts on “Skeletal Muscle 2- Myofibers

  1. I can't wait for this channel to hit one million subscribers soon. Its just amazing and I hope when my son grows up this stuff still be available and free also. I have an 11month old "Yusuf" and he is darling. I love you, Yusuf. maybe one day he will see this comment , who knows 😉

  2. I love Wendy's enthusiasm and the way she isn't super serious during her lecture videos. Some of the material I have to study for Human Physiology is so dry and dull. Having someone make it lighthearted and fun really makes the information more accessible, and holds an audience's attention. Wendy, please take a sabbatical to England one day! I'd love you to teach my fellow students and I!

  3. Wendy, this topic is a very hard one, cz it has many steps involved. I gave up on my book, closed it and hoped Wendy could save me and thats how I landed here.
    My concepts of this chapter are clear and A1 now cz of you.Lots of love from UK ❤

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