Table 1: Threshold Stimulus (V) Muscle Stimulation AMU SCIN 130

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4.   In this exercise, you will use an oscilloscope to examine the effect of varying load (weight) on frog skeletal muscle action.  To begin, click on the pull down menu of the “Muscle” button to select the type of muscle you would first like to test.  Making sure that the oscilloscope is set to “0.0 V”, click the “Apply Stimulus” button.  As you do so, pay close attention to the trace readout on the screen; you are looking specifically for a spike in the straight line to be produced.  If no spike is observed, use the upward pointing arrow on the oscilloscope to increase the voltage to the next highest level and then click “Apply Stimulus”.  Keep repeating this procedure until you observe the production of a spike in the oscilloscope trace readout.  At that point, note the voltage in the “0g” load weight for that muscle in Table 1 and round all values to the 1st (tenths) decimal place.  NOTE:  If no spike is observed, be sure to click “Apply Stimulus” at least 3 times to make sure the muscle received the stimulus properly.

5.   When you are through, you will then need to repeat the above steps using the varying loads (weights).  To do so, drag the 5g weight to the hook attached to the frog muscle and then proceed as you did to test the muscle action in step 4 above.  When you are through testing the 5g weight, repeat these steps using each of the four remaining loads.

6.   When you are completely finished testing all variables for the muscle type selected, you will need to repeat this procedure for ALL three remaining muscle types.  Remember, you can always click the “Reset” button to clear your experiment and start fresh.  Be sure to appropriately note all of your data in Table 1 below, rounding all threshold stimulus values to the 1st (tenths) decimal place.

7.   Answer Lab Questions 1-14 below.

Table 1:  Threshold Stimulus (V)

Load   Lower Forelimb Muscle   Upper Forelimb Muscle   Calf Muscle   Thigh Muscle
0g            
5g            
10g            
20g            
40g            
80g            

Lab Questions:

1.    Smooth muscle:
a.    Is voluntary
b.   Is found in the heart
c.   Is found in lining the intestines
d.   All of the above

2.    Skeletal muscle:
a.    Is involuntary
b.   Is made up of muscle fibers
c.   Is attached to bone via ligaments
d.   All of the above

3.   In skeletal muscle:
a.    The greater the number of muscle fibers responding to a stimulus, the greater the strength of the contraction
b.   the fewer the number of muscle fibers responding to a stimulus, the greater the strength of the contraction
c.   the actual number of muscle fibers responding to a stimulus has no effect on the strength of the contraction

4.     An oscilloscope:
a.    Provides stimulus to a tested muscle
b.   Adds weight (load) to a tested muscle
c.   Measures a twitch response of a tested muscle
d.   A and C
e.   All of the above

5.   At the point of muscle overload:
a.    Skeletal muscle contracts steadily (tetany)
b.   Skeletal muscle contracts and relaxes repeatedly
c.   Skeletal muscle does not contract at all
 
6.   A skeletal muscle’s “threshold of stimulation”:
a.    Is determined by the lowest voltage stimulus needed to elicit a muscle twitch
b.   Varies with muscle type
c.   Is not altered by the application of muscle load
d.   A and B

7.    In response to a stimulus, skeletal muscle fibers:
a.    Always contract to 25% of their potential ability
b.   Always contract to 50% of their potential ability
c.   Always contract 100% of their potential ability
d.   None of the above

8.   Based upon your experimental data, which muscle type exhibited the lowest threshold of stimulation in all conditions tested?
a.    Lower forelimb muscle
b.   Upper forelimb muscle
c.   Calf muscle
d.   Thigh muscle

9.    Based upon your experimental data, which muscle type(s) did not reach the point of muscle overload?
a.     Lower forelimb muscle
b.   Upper forelimb muscle
c.   Calf muscle
d.   Thigh muscle

10.    Based upon your experimental data, which muscle tested appears most capable to provide the contraction strength needed for a frog to jump?
a.    Lower forelimb muscle
b.   Upper forelimb muscle
c.   Calf muscle
d.   Thigh muscle

11.   Based on the results of your investigation, what conclusions can you draw about the relationship between a muscle's workload and its threshold of stimulation?

12.   Why would a muscle's threshold of stimulation change as its workload changes?

13.   Which muscles were able to contract under the greatest loads? What does this suggest about the role these muscles play in frog movement?

14.   Describe an experiment you might perform to determine which leg muscles of a frog are important for jumping long distances.

An experiment to determine which leg muscles of a frog are important for jumping long distances is to fill out worksheet about different muscle types and decide which affects locomotion the most, learn names, classifications of skeletal muscles, color a coded diagram of frog muscles with the different muscle types, learn about the different types of skeletal muscles.

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