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PhysioEx 8.0 - Answers Ex 2
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aangell
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Single Stimulus
Activity 1:  Identifying the Latent Period

1.How long is the latent period? 2.22      msec
2.Does the latent period change with different stimulus voltages? No

Activity 2:  Identifying the Threshold Voltage

1.What do you see in the Active Force display? 0
2.What is the threshold voltage?    .8       V
3.How does the graph generated at the threshold voltage differ from the graphs generated at voltages below the threshold? There is a small rise in the graph indicating activity

Activity 3:  Effect of Increases in Stimulus Intensity

1.How did the increases in voltage affect the peaks in the tracings? At first there was a noticeable difference in the peaks increasing, but as the voltage increased the peaks began to look the same.
2.How did the increases in voltage affect the amount of active force generated by the muscle? The Active Force increased then leveled off at 1.82
3.What is the voltage beyond which there were no further increases in active force? Maximal voltage:   8.5        V
4.Why is there a maximal voltage?  What has happened to the muscle at this voltage? 
 At the maximal voltage, all muscle fibers are responding (contracting) to the stimulus applied. Below this voltage, some fibers remain that will not be stimulated by the applied stimulus.
5.An individual muscle fiber follows the all-or-none principle—it will either contract 100% or not at all.  Does the muscle we are working with exhibit the all-or-none principle? 
Think about this, the muscle we are working with consists of many, many fibers—not one individual fiber. And because the all or none only applies to individual fibers and motor units (all fiber in a motor unit contract when the nerve is stimulated). As whole muscle force increases more motor units are recruited. If the all-or-none principle applied to the whole muscle what would you have observed?



Multiple Stimulus
Activity 4:  Treppe

1.What do you observe? Each time the single stimulus button was hit the force in gms gets higher. The rises in the graph are also slightly different.

Activity 5:  Summation

1.What is the active force of the contraction?  1.82     gms
2.What is the active force now?  2.76     gms
3.Was there any change in the force generated by the muscle? yes
4.Was there any change in the force generated by the muscle? yes
5.Why has the force changed? The force changed because the fibers that responded to the first stimulus were still recovering & not able to respond to the second stimuli
6.Do you see the same pattern of changes in the force generated? yes
7.Does the force generated change with each additional stimulus?  If so, why? Yes, the force increases with each stimuli

Activity 6:  Tetanus

1.What begins to happen at around 80 msec? The rises begin to level off and the active force begins to decrease
2.What is this condition called? Tetanus
3.How does the trace at 130 stimuli/sec compare with the trace at 50 stimuli/sec?
4.What is this condition called?
Fused tetanus
5.At what stimulus frequency is there no further increase in force? 146
6.What is this stimulus frequency called? Maximal Titanic Tension

Activity 7:  Fatigue

1.In fatigue, what happens to force production over time? The Active Force decreases.

Isometric and Isotonic Contractions
Activity 8:  Isometric Contractions

1.Looking at your graph, what muscle lengths generated the most active force? (provide a range)     70           to       80          mm
2.At what muscle length does passive force begin to play less of a role in the total force generated by the muscle?    50           mm
3.Looking at your graph, at what muscle length does passive force begin to play a role in the total force generated by the muscle?  80             mm
4.The graph shows a dip at muscle length = 90 mm.  Why is this?
5.What is the key variable in an isometric contraction? Total Force

Activity 9:  Isotonic Contractions

1.How much time does it take for the muscle to generate 0.5 grams of force?          3.77 msec
2.At what point in the trace does the muscle shorten? At the very beginning
3.You can observe from the trace that the muscle is rising in force before it reaches the plateau phase.  Why doesn’t the muscle shorten prior to the plateau phase?
4.Did it take any longer for the muscle to reach the force it needed to move the weight? No
5.How does this trace differ from the trace you generated with the 0.5 gram weight attached?      The tracing is flat, it stays the same.
6.Examine the plot data and your numerical data.  At what weight was the velocity of contraction the fastest?  2.0      grams

7.What happened when you attached the 2.0 gram weight to the muscle and stimulated the muscle?  How did this trace differ from the other traces?  What kind of contraction did you observe? Isometric? 
8.What kind of trace did you get? A flat line
9.What was the force of the contraction?   .5      grams -passive
10.With the 1.0 gram weight, what kind of trace did you get?  What was the force of the contraction?  1.0     grams – passive / Flat line
11.With the 1.5 gram weight, what kind of trace did you get?  What was the force of the contraction?  1.51     Grams – passive / Flat line
12.With the 2.0 gram weight, what kind of trace did you get?  What was the force of the contraction?  ?  1.86     grams ?  Small rise in the beginning then leveled off
13.Describe your four tracings and explain what has happened in each of them. ?  The lines for the 90 and 60 length were both similar creating a rise in the line. Lines for the 80 and the 70 were the same, leveling off the active force for a few seconds before decreasing
14.What muscle length(s) generated the fastest contraction velocity? 90 and 60

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Reply# 1
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4 years ago

Thanks!!!!!! I need this Smile you're my angel!



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Reply# 2
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4 years ago

AAHHH Thank you so much you are my Angel as well  Grin



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Reply# 3
gobuckeyes
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3 years ago

In Activity 4, you looked at the effect of stimulating the muscle multiple times in a short period with complete relaxation between the stimuli.
Describe the force of contraction with each subsequent stimulus.



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Reply# 4
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3 years ago

In Activity 4, you looked at the effect of stimulating the muscle multiple times in a short period with complete relaxation between the stimuli.
Describe the force of contraction with each subsequent stimulus.

The force .



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