Skeletal Muscle Fibers: Types (Nursing)

00:00 So now let's discuss the different types of muscle fibers that are found in our muscles.

00:06 We actually have several different types of muscle fibers and not all muscle fibers are created equal.

00:12 We have slow oxidative muscle fibers, fast oxidative-glycolytic muscle fibers, and fast glycolytic muscle fibers.

00:23 Let's talk a little bit about how each one of these are used in the body.

00:29 So now let's discuss the structural characteristics of each of these different types of muscle fibers.

00:35 First, in slow oxidative fibers also called SO fibers, you have a large amount of myoglobin.

00:44 Myoglobin is the molecule that is bound by oxygen because you have a large amount of oxygen, you also have a large amount of mitochondria, and this is going to appear red.

00:58 So if you like your steak rare, you're actually not seeing blood when you cut into the steak.

01:04 It is actually the myoglobin that you're visualizing.

01:09 The second type of fiber, the fast oxidative-glycolytic fibers is also going to have a large amount of myoglobin, although it has less than the slow oxidative fibers.

01:22 These also have a lot of mitochondria and they're going to appear a reddish pinkish color.

01:29 Again, this is due to the amount of myoglobin.

01:33 Finally, we have the fast glycolytic fibers.

01:37 In the fast glycolytic fibers, you're going to have a very small amount of myoglobin.

01:44 Since you do not have this molecule that oxygen binds to that means you also have very little oxygen in these fibers.

01:53 So we also have very few mitochondria, and because there is not a lot of myoglobin, they appear very white or pale.

02:03 So now let's talk about the functional characteristics of each.

02:07 In your slow oxidative muscle fibers, recall that we have a large amount of myoglobin as well as mitochondria.

02:16 The rate of ATP in these cells is going to be very slow.

02:21 So the rate of ATP hydrolysis is very slow.

02:25 However, we are going to yield a very high amount of ATP because we are going to undergo cellular respiration.

02:35 In the fast oxidative-glycolytic fibers, we have an intermediate amount of myoglobin and mitochondria and therefore we have an intermediate ability to make ATP.

02:48 These fibers are going to go through both aerobic and anaerobic glycolysis.

02:56 In these cells, ATP hydrolysis is pretty fast.

03:00 And we are going to use this in situations where we need to use a little bit of energy quickly.

03:10 Finally, we have the fast glycolytic fibers.

03:14 In the fast glycolytic fibers, we do not have a large myoglobin content and we also have very few mitochondria.

03:22 Because of this, we are unable to undergo aerobic respiration and we must go through anaerobic glycolysis.

03:31 In this case, we're going to get a very fast, quick production of ATP in the cell, but it's also going to be expended pretty quickly.

03:42 So let's think about when we would use each of these types of fibers.

03:48 What fiber type do you think a marathon runner would most likely use? A marathon runner is usually going to use a large amount of SO or slow oxidative fibers.

04:08 The reason why is because they are running at a slow enough pace that they're allowing oxygen to come in, and cellular respiration to occur.

04:18 Also a marathon is very long, so you need a lot of energy.

04:23 Second, what fiber type does a shot-putter most heavily rely on? A shot-putter is most likely to use the fast glycolytic fibers.

04:40 The reason why is a shot-putter is going to need a very short burst of energy.

04:47 Finally, what fiber type does a soccer player most heavily rely on? Soccer players are most likely going to use fast oxidative-glycolytic as they are going to go through periods where they're going to have more energy being expended maybe as they're sprinting down the field.

05:12 And then they'll also go through periods where they get a little bit of rest and can undergo the slower cellular respiration that happens in the oxidative fibers.