00:00:08
all right Niners in this video we're
00:00:09
going to talk about the skeletal muscle
00:00:10
fiber types okay so when we take a look
00:00:13
at a skeletal muscle you know most
00:00:15
people think just oh it's just muscle
00:00:17
fibers well technically those muscle
00:00:19
fibers or those muscle cells they differ
00:00:22
okay so for example what I wanted to
00:00:24
show you before we get into each one of
00:00:25
these actual muscle fiber types that way
00:00:27
I can actually like completely clarify
00:00:29
something
00:00:30
let's say I take the actual muscle if
00:00:32
you guys remember from the structure of
00:00:34
skeletal muscle video we took and and
00:00:37
took the section of a muscle belly then
00:00:39
we had around we had inside of the
00:00:40
muscle belly we had those bundles of
00:00:42
muscle fibers called a fasle well right
00:00:45
here this whole bundle here a
00:00:47
cross-section of it this is our fasle so
00:00:49
this whole thing right here is
00:00:51
specifically the
00:00:55
fasle now in this fle there's consisting
00:00:58
of multiple muscle fibers now the thing
00:01:02
is is that each one of these muscle
00:01:03
fibers are not all the same they can
00:01:06
differ so for example we're going to
00:01:07
talk about three main types of muscle
00:01:10
fibers type
00:01:14
one type 2
00:01:17
a and the last one which will be type 2
00:01:23
x now some people will be like oh well
00:01:26
what about type 2 B type 2x is mainly in
00:01:29
humans type 2X X is in other I'm sorry
00:01:30
type 2 B is in other different types of
00:01:32
animals so in this video we're going to
00:01:34
talk about type one type 2 a and type 2x
00:01:39
tissues okay or skeletal muscle fibers
00:01:41
so when I actually look at each one of
00:01:43
these structures it might look like a
00:01:45
big muscle but technically what I'm
00:01:48
trying to represent here is that this is
00:01:50
a muscle fiber type this is a muscle
00:01:53
fiber type and this is a muscle fiber
00:01:55
type okay so that we're clear all right
00:01:58
so first thing we're going to do is
00:01:59
we're going to start here with this
00:02:00
skeletal muscle fiber type and we're
00:02:02
going to denote this one to be type one
00:02:06
okay so this skeletal muscle fiber type
00:02:07
is specifically type one now here's the
00:02:12
thing type one skeletal muscle fibers
00:02:15
also have another name and we we'll
00:02:18
decipher that name as we go through its
00:02:19
different types of structural
00:02:20
characteristics and metabolic
00:02:21
characteristics and really what it's
00:02:23
functionally uh for and that name is
00:02:26
called slow
00:02:32
oxidative muscle fiber okay so this is a
00:02:35
slow oxidative muscle fiber and
00:02:38
sometimes they even add on to it they
00:02:39
say red slow oxidative I'll do that just
00:02:43
for the heck of it I'll put that right
00:02:44
here it's technically
00:02:46
red slow oxidative that's really going
00:02:50
to help us to decipher what makes this
00:02:52
skeleton muscle fiber type different
00:02:54
from the other two skeletal muscle fiber
00:02:57
types all right the first one let's go
00:02:59
ahead and go through each one of these
00:03:01
uh skeletal muscle fiber types in a
00:03:02
specific order okay so structurally how
00:03:06
is this type one skeletal muscle fiber
00:03:09
different from these other two well the
00:03:11
first thing about its structure is that
00:03:13
if you guys
00:03:14
notice this muscle fiber is a lot
00:03:17
smaller than the other two so because
00:03:20
this muscle fiber is a lot smaller than
00:03:22
the other two it should be the smallest
00:03:24
muscle fiber so its overall fiber
00:03:27
diameter should be a lot less so in that
00:03:30
that's the case then the fiber diameter
00:03:33
should be very small so it should have a
00:03:36
decrease or a small let's say let's
00:03:37
actually not put decrease let's put
00:03:41
small
00:03:44
fiber and all fiber is just a muscle
00:03:46
cell
00:03:49
diameter because that's one thing so if
00:03:52
you look at the diameter of this guy as
00:03:54
compared to all the rest of these it's a
00:03:57
lot smaller d diameter
00:04:02
okay that's one thing what else is
00:04:05
structurally different from this one all
00:04:07
right let's look at it's name red what
00:04:09
is the red really coming from now
00:04:12
muscles are highly vascular highly
00:04:15
vascular but specifically the most
00:04:17
special type the most highly
00:04:18
vascularized muscle fibers are the red
00:04:22
slow oxidative muscle fibers they have a
00:04:23
large amount of capillary density so if
00:04:26
that's the case then let's say I
00:04:27
represent this with a blood vessels
00:04:29
right so if that's the case then this is
00:04:31
going to have a large amount of blood
00:04:34
vessel Supply this is going to have a
00:04:37
large amount of capillary Supply if this
00:04:40
has a large amount of capillary
00:04:44
Supply then what does that mean for its
00:04:47
actual color that means that its color
00:04:50
is going to be a nice bright red why is
00:04:52
it going to be a nice bright red the
00:04:54
reason why it's going to be a nice
00:04:55
bright red is because it's carrying
00:04:57
blood through there right so if it's
00:04:59
carrying blood through there what's
00:05:00
special about blood blood is having
00:05:03
hemoglobin in it and hemoglobin is
00:05:05
actually what causes the actual blood to
00:05:07
look red specifically red blood cells so
00:05:09
it's having a lot of blood flowing
00:05:11
through that area so because there's a
00:05:12
lot of blood so let's represent blood
00:05:14
flowing through here and out here what
00:05:17
type of color is it going to give off
00:05:18
it's going to give off a nice reddish
00:05:20
color and the reason why is
00:05:23
because this has a high capillary
00:05:26
density so a very high
00:05:31
capillary
00:05:33
density and then again if that's the
00:05:35
case then if it has a high capillary
00:05:37
density what color would you expect this
00:05:40
actual skeletal muscle fiber to exist as
00:05:43
it would be very very red because
00:05:45
there's a large amount of capillary
00:05:47
supplying it so if that's the case then
00:05:49
it's going to have a nice
00:05:52
reddish
00:05:53
Hue and huge is is kind of you know
00:05:56
color all right so nice reddish hue okay
00:05:59
so what do we know right now first thing
00:06:01
we know smallest diameter muscle fiber
00:06:05
second thing we know high amounts of
00:06:06
capillary density so a lot of blood
00:06:08
supplying this muscle fiber because
00:06:10
there's a lot of capillary density it's
00:06:11
going to have a nice reddish Hue and
00:06:14
also think about this if you have a
00:06:16
small skeletal muscle fiber does it take
00:06:19
as many capillaries to actually uh cause
00:06:21
that reddish Hue on that that structure
00:06:23
no if I take a big huge skeleton muscle
00:06:26
and I have a decent amount of capillary
00:06:28
density it's going to take a lot of
00:06:29
capillaries in order to produce off that
00:06:31
reddish Hue on a large skeletal muscle
00:06:33
fiber as compared to a smaller skeletal
00:06:35
muscle fiber so a smaller skeletal
00:06:37
muscle fiber even though the capary
00:06:39
capillary density is really high it
00:06:40
doesn't take as much capillaries to
00:06:43
produce that nice reddish Hue as
00:06:44
compared to a large skeletal muscle
00:06:46
which require significantly large
00:06:48
amounts of capillaries to produce that
00:06:50
same reddish Hue okay that's that part
00:06:54
next thing I want to talk about what
00:06:55
about organel in this area what about
00:06:57
the organ LS there's a very important
00:06:59
organel that is important for these
00:07:01
skeletal muscle fibers okay this organel
00:07:04
is specifically the mitochondria so
00:07:07
let's have here the
00:07:10
mitochondria this one has a significant
00:07:14
amount of
00:07:15
mitochondria very very significant
00:07:18
amounts of mitochondria now that's
00:07:20
important and we're going to talk about
00:07:21
that when we get into the metabolic
00:07:23
characteristics of these guys but again
00:07:25
I want you to understand that this one
00:07:26
has significant amounts of mitochondria
00:07:30
now what are mitochondria important for
00:07:32
if you guys remember mitochondria are
00:07:34
really important for ATP production
00:07:37
they're the powerhouses of our cells
00:07:39
right so because they're the powerhouses
00:07:41
of our cells what are they basically
00:07:43
doing if you guys remember they can take
00:07:45
certain types of energy sources like
00:07:47
what they can take
00:07:50
glucose they can take amino acids they
00:07:53
can take fats right and what can they do
00:07:56
with that they can utilize that and do
00:07:59
what
00:08:00
use that in the presence of what has to
00:08:02
be there though in order for this
00:08:04
reaction to actually occur you need to
00:08:06
have
00:08:07
oxygen you need oxygen what does that
00:08:11
mean when you need oxygen when a pathway
00:08:12
requires oxygen it's an aerobic pathway
00:08:16
so it's an aerobic pathway and the
00:08:19
overall result out of this is that'll
00:08:21
lead to the formation of
00:08:23
ATP so if that's the case and if these
00:08:26
guys need oxygen and they're
00:08:28
metabolizing fat fats and glucose and
00:08:30
amino acids to be able to produce ATP
00:08:33
and you they have plentiful amounts of
00:08:35
mitochondria what does that mean for the
00:08:37
ATP formation they're going to have a
00:08:38
decently High ATP formation so these
00:08:41
types of skeletal muscle fibers
00:08:43
generally produce a significant amount
00:08:45
of ATP by cellular aerobic cellular
00:08:49
respiration but let's come back again
00:08:51
what did I say about the mitochondria so
00:08:52
that we can continue to keep labeling
00:08:54
here we said that there's a decent
00:08:55
amount of mitochondria so they have a
00:08:57
significantly large amount of
00:08:59
mitochondria so large amount
00:09:03
of
00:09:04
mitochondria okay so now that we've done
00:09:07
that we can relate the Structural
00:09:09
Concepts to the metabolic Concepts
00:09:12
here okay first off we talked about
00:09:16
mitochondria what did we say was one of
00:09:19
the metabolic characteristics here
00:09:20
because they have significant amounts of
00:09:22
mitochondria they're primarily going to
00:09:24
be depending on oxygen so the primary
00:09:27
way upon which these cells produce
00:09:29
energy or ATP has to be aerobic cellular
00:09:32
respiration so these skeletal muscle
00:09:35
fibers primarily depend
00:09:37
upon uh
00:09:40
aerobic
00:09:43
cellular
00:09:46
respiration okay so for example they
00:09:49
would use they would undergo kreb
00:09:52
cycle they would undergo the electron
00:09:54
transport chain reactions they would
00:09:57
undergo many many different types of
00:09:58
reactions and lead to the production of
00:10:01
ATP by what type of process are they
00:10:03
producing ATP this is under
00:10:08
oxidative
00:10:13
phosphorilation okay so that's one thing
00:10:16
we know that they're very very dependent
00:10:18
upon aerobic cellular respiration
00:10:20
another
00:10:21
thing because these skeletal muscle
00:10:24
fibers are small They Don't Really and
00:10:27
oh before we even do that what what does
00:10:29
their name suggest red okay that means a
00:10:32
lot of capillary density it means
00:10:33
something else in a second
00:10:36
slow oh you know what these these muscle
00:10:38
fibers must contract very slow and that
00:10:41
is true these skeletal muscle fibers are
00:10:44
the slowest in contractility speed so
00:10:47
the rate at which these muscles are
00:10:48
Contracting are very slow and we'll see
00:10:50
why here in just a second so again what
00:10:52
is up with the contractile speed here
00:10:54
very
00:10:55
slow contractile
00:11:00
speed so the rate of contraction is a
00:11:03
lot lower in this skeletal muscle fiber
00:11:05
type and the reason why is it has a
00:11:09
decreased
00:11:11
mein
00:11:14
atpa activity okay we talked about this
00:11:18
a little bit in the actual skeleton
00:11:21
muscle contraction video If you guys
00:11:23
remember let's say here I have thin
00:11:27
filament and on the thin filament you
00:11:29
have
00:11:31
actin and if you guys remember we had
00:11:33
the thick filament right and the thick
00:11:35
filament specifically consists of these
00:11:37
mein right with the mein heads that were
00:11:40
connecting with the actual actin
00:11:42
remember in order for us to detach the
00:11:45
myin we had to bind ATP but then what
00:11:48
else did we say remember we told you
00:11:50
that in the first step of that whole
00:11:52
process there was
00:11:54
hydraulis what does that mean to hydroly
00:11:56
the ATP well you remember we said that
00:11:57
it actually is breaking the second and
00:11:59
third phosphate that bond between those
00:12:01
two there's a special enzyme that's
00:12:04
actually on the
00:12:06
mein on this mein it has a special
00:12:11
enzyme
00:12:12
component and what that enzyme component
00:12:14
does is it actually breaks that bond
00:12:16
between the ATP and then converts it
00:12:18
into ADP and anorganic phosphate which
00:12:22
helps to be able to put it into that
00:12:24
cocked position right this enzyme that's
00:12:27
a component of the mein that enzyme so
00:12:30
imagine again if I draw it over here on
00:12:31
the side imagine
00:12:34
here is the enzyme okay and this enzyme
00:12:38
is actually a part of
00:12:42
mein it's actually a component of the
00:12:44
myosin and what happens is it's breaking
00:12:47
down the
00:12:48
ATP what is this enzyme called this
00:12:51
enzyme is called
00:12:52
aasin ATP now think about this for a
00:12:56
second if there's the activ ity of this
00:12:59
enzyme is decreased will he break down
00:13:01
as much ATP no if he doesn't break down
00:13:03
as much ATP will he be able to detach
00:13:05
the myosin from the actual acting very
00:13:07
quickly no if he doesn't detach it will
00:13:10
he be able to will he um will the will
00:13:13
he be able to cause the cocked position
00:13:15
and then reattach to the next actin
00:13:16
quickly no and so then will he be able
00:13:19
to create the power stroke quickly no so
00:13:21
the overall concept is is that because
00:13:23
he's decreasing the meas and atpa
00:13:25
activity this whole Detachment and then
00:13:29
hydrolysis and then the whole power
00:13:31
stroke and then rep putting on the ATP
00:13:33
that whole activity the sliding filament
00:13:35
theory is going to decrease therefore
00:13:37
the contraction speed will
00:13:40
decrease another thing to think about if
00:13:42
it's undergoing aerobic cellular
00:13:44
respiration doesn't it have to go
00:13:45
through many many different types of
00:13:47
Pathways so it might take a little bit
00:13:49
longer to be able to produce significant
00:13:50
amounts of ATP because you know there's
00:13:52
two types of phosphorilation substrate
00:13:54
phosphorilation and oxidative this cell
00:13:58
primarily depends upon
00:13:59
oxidative and oxidative we already said
00:14:02
produces very
00:14:04
significant large amounts of
00:14:09
ATP
00:14:10
okay next thing about this uh skeletal
00:14:13
muscle fiber we know that it contracts
00:14:15
slowly we know that the speed is very
00:14:18
slow but here's what's really cool about
00:14:20
this muscle because it contracts slow it
00:14:23
can last a long time okay so because
00:14:26
it's Contracting very slow the activity
00:14:29
this skeletal muscle fiber can go on for
00:14:31
a long period of time not only that
00:14:34
think about energy- wise if I have
00:14:35
enough energy I can carry out an
00:14:38
activity for a decent amount of time but
00:14:40
if I don't have enough energy that
00:14:42
activity won't be able to go on for a
00:14:43
very long time so what two things are
00:14:44
contributing to this muscle being able
00:14:46
to carry out this activity for a long
00:14:48
time one is the slow contractile speed
00:14:51
and the other one is the large amounts
00:14:52
of ATP produced so
00:14:55
therefore we can say that this one is is
00:14:59
actually going to be fatigue resistant
00:15:02
very very fatigue
00:15:06
resistant high amounts of fatigue
00:15:08
resistance so this muscle can go on for
00:15:11
a long period of time can carrying out
00:15:13
its activity if you really want to know
00:15:15
it can carry out this activity for
00:15:18
hours many hours okay okay but here's
00:15:22
the
00:15:23
thing because it's fatigue
00:15:26
resistant it actually is not going to be
00:15:29
very strong it doesn't generate a lot of
00:15:32
power and that should make sense because
00:15:34
of this decreased mice and atpa enzyme
00:15:37
so because it's smaller a smaller
00:15:39
diameter fiber and because of this mice
00:15:41
and atps activity and the slow
00:15:43
contractile speed it's not going to be
00:15:45
able to generate a decent amount of
00:15:46
power to move a heavy load so therefore
00:15:49
because it doesn't have a lot of
00:15:51
power do you know what's called there's
00:15:52
what's called a motor unit what is a
00:15:55
motor unit what is a motor unit a motor
00:15:57
unit
00:16:00
is two things it's a motor
00:16:04
neuron and all the muscle fibers it's
00:16:10
supplies now there's What's called the
00:16:13
size principle the what with the
00:16:15
recruitment concept and recruitment just
00:16:17
means if you have a motor
00:16:21
unit if you have more motor units you
00:16:24
can recruit more muscle fibers but now
00:16:26
let's look at the side let's look at the
00:16:28
aspect of the muscle fibers okay now if
00:16:31
we look at this from the respect of the
00:16:32
muscle fiber concept not the motor unit
00:16:35
concept if we want to be able to move
00:16:38
something right something you know
00:16:40
really really heavy it's going to
00:16:42
require okay a specific type of activity
00:16:46
but these muscles are very special and
00:16:48
the reason why they're very special is
00:16:50
they're not used to carrying very heavy
00:16:52
loads they're so because of that they're
00:16:54
not used to carrying very heavy loads
00:16:56
these muscle fibers are going to get
00:16:58
recruited first okay they're not used to
00:17:01
carrying heavy loads so the order of
00:17:03
muscle fiber recruitment in other words
00:17:05
the motor units so the motors neurons
00:17:07
that are actually stimulating those
00:17:08
muscle cells to contract this muscle
00:17:11
fiber will be the first one to be
00:17:13
stimulated so type one muscle fibers are
00:17:16
red slow oxidative muscle fibers are the
00:17:18
first muscle fiber to get recruited and
00:17:21
the reason why is it produces very
00:17:25
little
00:17:27
power so because it produces very little
00:17:29
power you don't really need this muscle
00:17:31
to be recruited last you just want to
00:17:33
get through that muscle quickly and then
00:17:34
move on to the other types of muscle
00:17:36
fibers okay so this is the one that gets
00:17:38
recruited
00:17:39
first so again if we have a motor neuron
00:17:42
here and here's your motor
00:17:45
neuron this motor neuron will actually
00:17:47
recruit this muscle fiber first so it
00:17:50
under goes first
00:17:53
recruitment
00:17:55
okay so this is the first recruitment
00:17:57
muscle fiber
00:17:59
next
00:18:01
concept okay now this skeletal musle
00:18:04
fiber is going to be depending upon
00:18:06
oxygen and one of the pathways that
00:18:08
requires oxygen a decent amount of it
00:18:10
and what's really special about this
00:18:12
muscle fiber is because it doesn't
00:18:13
undergo Anor robic processes it's going
00:18:15
to depend upon oxygen and it's going to
00:18:17
store a special type of storage molecule
00:18:21
and that storage molecule is called
00:18:24
triglycerides it's called
00:18:26
triglycerides and these muscle fi types
00:18:29
are very special because they store a
00:18:30
lot of their energy in the form of
00:18:34
triglycerides and if you guys remember
00:18:37
we talked about over here with fats what
00:18:39
do triglycerides actually do whenever
00:18:42
they go into the mitochondria if you
00:18:44
guys remember when these guys go into
00:18:47
the
00:18:49
mitochondria they undergo a special
00:18:51
process and that special process is
00:18:53
called beta oxidation right specifically
00:18:55
the fatty acids and when they undergo
00:18:57
this beta oxidation what can come out of
00:18:59
this result this you can produce tons of
00:19:02
ATP and again this is the result of beta
00:19:06
oxidation specifically for the fatty
00:19:08
acids and then the glycerol can actually
00:19:10
go into a spe specific glycolytic
00:19:13
pathway and that glycolytic pathway will
00:19:15
also lead to the production of
00:19:17
ATP
00:19:19
now again if we're looking at the
00:19:22
skeleton muscle fibers their main source
00:19:24
of energy storage of fuel is in the form
00:19:26
of triglycerides so how do they store
00:19:28
store their energy they store their
00:19:30
energy primarily in the form
00:19:35
of
00:19:39
triglycerides that's their main source
00:19:41
of energy storage is in the form of
00:19:42
triglycerides now one more thing you
00:19:44
know the skelet MUSC have a special
00:19:46
protein a special protein that it has
00:19:48
within it this special protein is
00:19:51
something
00:19:53
like hemoglobin it's something like
00:19:56
hemoglobin it's not hemoglobin but it's
00:19:58
something like
00:19:59
him and this protein is called myoglobin
00:20:03
you see this protein here this it's
00:20:05
smiling at you because it's helping us
00:20:06
right all the time helping out your
00:20:08
skeletal muscles this protein is called
00:20:12
myo globin and what myoglobin is really
00:20:15
cool at being able to do is it
00:20:18
temporarily holds on to the oxygen so
00:20:20
whenever blood is flowing through this
00:20:22
area it drops off oxygen to this
00:20:25
myoglobin and the oxygen can bind onto
00:20:27
the myoglobin and Ami globin can hold on
00:20:29
to this oxygen and whenever the tissue
00:20:31
cell needs it it can drop that oxygen
00:20:34
off right so whenever it's actually
00:20:36
relaxing the blood is coming to the
00:20:38
tissue is dropping off oxygen when the
00:20:40
skeletal muscle gets ready to contract
00:20:41
right we need ATP so what do you need in
00:20:43
order to produce ATP oxygen the oxygen
00:20:46
can get used to produce ATP so we need
00:20:48
to have a lot of myoglobin so the amount
00:20:50
of myoglobin and the skeletal muscle
00:20:53
fiber should be very very high so we
00:20:55
should have a lot of myoglobin too okay
00:20:58
all right so because these muscle fibers
00:21:01
are having to be able to specifically
00:21:03
produce lots of ATP they contract very
00:21:05
slowly they're very fatigue resistant
00:21:06
you're going to want these to be muscles
00:21:08
that you can carry out some activity for
00:21:10
a long period of time so one of the
00:21:13
things that most people you if you think
00:21:15
about is marathon runners so this is
00:21:18
very good for those people who are going
00:21:19
to run marathons so if you're one of
00:21:21
those individuals who wants to go and
00:21:22
run a marathon okay so run marathons
00:21:28
these are some good muscle fibers that
00:21:30
are going to help you in that process
00:21:32
and the reason why is because you know
00:21:34
marathons I've never ran one but I from
00:21:36
what I understand you run long distance
00:21:38
right and so because of that you're
00:21:40
going to require a lots of ATP
00:21:43
production because your skeletal muscle
00:21:44
fibers are going to depend upon that ATP
00:21:46
in order for us to do that we have to
00:21:47
have a lot of aerobic cellular
00:21:49
respiration not only that but these
00:21:51
muscles are very fatigue resistant
00:21:52
because they have a high capillary
00:21:54
density a high amount of oxygen coming
00:21:55
to the area right and they have lots of
00:21:57
triglycerides is a concentrated source
00:21:59
of energy fuel so because of that that's
00:22:01
one thing but you know what else is
00:22:03
really important think about this what
00:22:04
is what is always always pushing down on
00:22:08
us gravity so because gravity is always
00:22:11
pushing down on us naturally it would
00:22:13
want to push our muscles like this right
00:22:16
so because of that we have muscles that
00:22:17
are constantly helping us to maintain
00:22:19
posture and maintain our body position
00:22:22
so those muscles that are are
00:22:24
anti-gravity or posture muscles are also
00:22:27
really important because they have to do
00:22:28
do that all day so if you're standing up
00:22:30
a lot if you're having gravity push down
00:22:32
these muscles are constantly helping you
00:22:33
to maintain your normal body posture so
00:22:36
again we can say anti-gravity muscles or
00:22:39
posture muscles so
00:22:41
anti-gravity
00:22:44
muscles and those would be a great
00:22:46
example of your
00:22:48
posture muscles okay helping to maintain
00:22:52
that nice posture okay that's our type
00:22:55
one are red slow oxidative muscle fibers
