Whole muscle 1- Introduction

Whole muscle 1- Introduction


– Hey, you guys. So in the last lecture
we introduced skeletal muscle. And we looked at the anatomical and structural characteristics
of skeletal muscle tissue, and then how that tissue is used to put together
skeletal muscle organs. And then we looked at axial
musculature, which is awesome. Today we’re going to look
at some of the functional consequences of the structure
of skeletal muscle tissue. And so we’re going
to kind of do this, like, in-and-out thing where
we’re going to explain stuff that we see
in muscle function everyday, and that we’re really
comfortable with. We’re going to explain it
on a cellular and sub-cellular level
of organization. So this lecture is pretty
interesting, but we have to make sure that we’re starting with
a really solid understanding of skeletal muscle structure. So I have this image
from the OpenStax textbook just as a reminder of where we
are and our overview, and then we’ll
go into addressing some specific questions. First of all, remember
that the skeletal muscle organ is the giant structure
that you can grab, like my oh, so
massive biceps brachii. Skeletal muscle organs are
made of bundles of muscle cells, and those bundles of muscle
cells are called fascicles. So each one of
these little bundles right here is a fascicle. I’m just going to label that,
because my brain– I got scolded for my
horrible handwriting. What?
One of my face-to-face students, it wasn’t even
a YouTube student, said, “Dude, can you type
your notes, please?” Sorry about that.
No. I’ll try to write
a little neater. So a fascicle is a bundle
of muscle cells. And we know that our muscle
cells are called myofibers. So check this out.
This is my myofiber. And all a myofiber is is a very
long, like, crazy unique cell.
It has multiple nuclei, and it’s filled with all these
really bizarre protein bundles. And this right here
is a protein bundle, and it’s called a myofibril. And myofibrils are
made up of myofilaments. So let’s just say that myofilament is the little
lines that I have right here. We know that we have thick
filaments and thin filaments. It looks like my thin
filaments are in light blue, and it looks like my thick
filaments are in red. And you can see that they
overlap each other, and that is the phenomenon known
as the sarcomere. Here are my thick filaments. Do you see that?
Remember we had the Z lines? This is the Z line. So from Z line to Z line,
that was one sarcomere. And remember that a sarcomere is
nothing more than overlapping thick and thin myofilaments. And remember
that the thick filaments had those little
contractile heads that grabbed a hold
of the thin filaments, and you slide across, and you actually get
the shortening of the muscle. So if we were to look at this,
if we were to contract this single
myofibril right here, it would shorten
in this direction. My massive biceps brachii
right here, when I flex my forearm,
you can barely see it. I can see it.
How’s that? Look. I’m flexing my massive biceps,
flexing my forearm, and I can feel
the muscle shortening. It’s shortening, because my
sarcomeres are going like that. Okay. We’re going
to rely on our understanding of sarcomeres and myofibrils when we’re talking
about some other characteristics in the rest of
this entire lecture. So make sure you’re comfortable with this little
image right here, so that you have a good, solid understanding going
into the next set of questions. The first and most
important question that we’re going to answer is
why am I so unbelievably strong?

2 Replies to “Whole muscle 1- Introduction”

  1. Thank you for doing these videos! I'm taking Human Anatomy online and it is very difficult, but watching these videos has helped me so much! Thanks again 🙂

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