AP Biology: Unit 8: Anatomy & Physiology: Virtual Lab #17: Muscle Stimulation
Procedure:
1. Open the Virtual Lab entitled “Muscle Stimulation”.
http://www.glencoe.com/sites/common_assets/advanced_placement/mader10e/virtual_labs_2K8/
labs/BL_13/index.html
2. The left side of the page contains background information and instructions in the “Question”
area. Read the background information found under the “Question” area first, and then continue
on to reading the procedure information posted there as well.
3. Complete the exercise as directed, recording any data or information needed in your Data Table
in your lab notebook.
a. 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 “0V”, 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 in
Table I in your lab notebook. 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.
b. 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 2 above. When you are through
testing the 5g weight, repeat these steps using each of the four remaining loads.
c. 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 your Table I in your notebook.
Table I: Threshold Stimulus (V)
Load
Lower
Forelimb
Muscle
0g
5g
10g
20g
40g
80g
Upper Forelimb
Muscle
Calf Muscle
4. When you are finished, please answer all of the questions below.
Thigh Muscle
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. B and C
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.