00:01
Greetings.
00:01
In this lecture
we will be discussing
the muscular system.
00:07
So first let's talk about
the different types of muscles
that are found in the body.
00:11
We have skeletal muscle tissue,
cardiac muscle tissue,
and smooth muscle tissue.
00:19
Of these three types of
muscle tissue,
we will focus mainly
on the skeletal muscles
for this lecture.
00:26
We will talk briefly about
cardiac muscles and smooth muscles
But we will talk more extensively
about those in other lectures.
00:36
So, first let's discuss
the functions of the
muscular tissue.
00:40
The muscle tissue is involved
in producing
body movements,
stabilizing the body's position,
storing and mobilizing substances
within the body,
and also generating heat.
00:55
Other properties as a
muscular tissue include
electrical excitability,
the ability to contract,
the ability to extend,
and finally,
the ability to return back
to its normal size or elasticity.
01:13
So now let's look at
the structural organization
of our skeletal muscles.
01:19
Starting with the largest part,
the actual muscle itself.
01:24
This organ is made up of vesicles
that are going to contain
muscle fibers
as well as blood vessels,
nerves,
and all of this is wrapped
in a connective tissue layer
known as the epimysium.
01:38
If we go inside or the next
smallest unit of the muscle,
we have the fascicles.
01:45
This is going to be a
bundle of muscle fibers
that are wrapped in a
connective tissue layer
known as
the perimysium.
01:52
If you like pulled pork,
you are actually looking at the
individual fascicles of the muscle.
02:01
The third level or
the next smallest level
is going to be the
muscle fiber itself.
02:07
We actually refer to muscle cells
as muscle fibers.
02:12
And this is because of the shape and
the organization of the cells.
02:17
In the muscle fiber we start out
with a connective tissue layer
known as the endomysium.
02:24
Inside of that we have the
sarcolemma.
02:27
The sarcolemma
would be synonymous
with the plasma membrane
of a regular cell.
02:34
Inside of the sarcolemma,
we have the sarcoplasm,
which is synonymous with the
cytoplasm of a regular cell.
02:42
Also inside of the cell,
we have myofibrils,
which are the contractile units
of the muscle,
as well as
multiple nuclei,
which is unique to muscle cells.
02:53
We also have mitochondria
which are very important
for allowing us to have the energy
for our muscles to contract.
03:00
And other structures include
transverse tubules,
the sarcoplasmic reticulum,
and the terminal cisterns,
which are going to be very important
for bringing in calcium
so that we can undergo
a muscle contraction.
03:14
When you look at a muscle fiber,
it has a striated or striped
appearance.
03:19
We'll discuss why this is later.
03:23
The final and smallest unit
of the muscle
is going to be the
myofibril.
03:28
As I said,
this is a contractile unit
of the muscle.
03:32
This threadlike
contractile element
is going to be found
within the sarcoplasm
of the muscle fiber
and it's going to extend
the entire length of the fiber.
03:42
Within the myofibril.
03:44
We have several different filaments
including thick and thin filaments.
03:49
We'll discuss these in more detail
shortly.
03:54
So speaking of the filaments
of the muscle,
we have
the thick filaments
which are going to be composed
of a protien known as myosin,
and then the thin filaments
which are composed of a protein
known as actin.
04:07
There are also several
regulatory proteins including
tropomyosin and troponin.
04:14
This part of the myofibril
these filaments are going to be
what we use
in order for our muscles to contract
or shorten.