Skeletal Strengths, Gastrocnemius And Muscle Types

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Skeletal muscles are made of three different muscle fiber types. All muscle fibers are having varying amounts of mitochondria in them. Mitochondria helps the muscle be able to manufacture ATP for contraction. To differentiate between the three muscles is based on their make up. Slow oxidative (SO) or type one muscle fibers are composed with the most mitochondria to help them be fatigue resistant. SO muscle fibers stain the darkest because the enzyme targeted by the stain is most abundant in this muscle fiber type. These muscle fiber types are the smallest in diameter which means they have the weakest contraction because they do not have many myofibrils. Subsequently, the second smallest in diameter are the fast-oxidative glycolytic (FOG) …show more content…
When looking at these under the microscope they are stained the lightest. These muscles are comprised of mainly myofibrils which means they are able to generate lots of force from one contraction. Even though they can generate lots of force they have the fewest mitochondria in them so they fatigue easily. We are doing this experiment to find out what types of muscle fibers the gastrocnemius and forearm muscles are built of. Being built from multiple muscle fiber types is important for maximal fatigue resistant and contraction. Before the experiment we hypothesized that the gastrocnemius would have the most type two b fiber types because they need to have a forceful contraction to help the frog jump. We also thought that the forearm and gastrocnemius would have the same about of each muscle fiber …show more content…
Once the cross section was on the leg we died it with a stain that specifically targets enzymes in the Citric Acid Cycle. From this step we were able to identify what muscle fiber types the cross section was made of because the slow oxidative (SO) were the darkest purple followed by fast oxidative glycolytic (FOG) and then fast glycolytic (FG) which were stained the lightest purple. Subsequently, we looked at the cross sections under the microscope to find the percent of each fiber type, average area of each fiber type, and percent area from these two muscle types. For further details, look at Eichinger, Skeletal muscle fiber types: determination through enzyme histochemistry. Biology 116 Laboratory Procedures, 2015.

Results

Figure 1. In the forearm of the frog muscle the average percent of each muscle type was SO with 55.4%, FOG had 30.4%, and FG was 12.8%. SO in the gastrocnemius had 23.2%. The FOG was 25.8% and FG in the gastrocnemius was composed of 50.8% muscle fiber. Figure 2. The average area for gastrocnemius for each muscle type was SO with 4,814 FOG with 19,934 and FG with 33,740. For the forearm muscle was 4,292 for SO, FOG had 12,084 and FG with 38,010.

Figure 3. The average percent area for SO muscle fiber types in the gastrocnemius was 7.6 million and in the forearm was 30 million. For the FOG in the forearm is 16 million and 10.7 million in the gastrocnemius.

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