PhysioEx 2

 

EXERCISE 2: MUSCLE PHYSIOLOGY

 

Activity 2: Identifying the Latent Period

 

How long is the latent period?  ____________ msec

 

Stimulus Voltage: ______________ V              Latent period: ______________ msec

 

Stimulus Voltage: ______________ V              Latent period: ______________ msec

 

Stimulus Voltage: ______________ V              Latent period: ______________ msec

 

Does the latent period change with different stimulus voltages?

 

 

 

 

 

Activity 3: Investigate graded muscle response to increase stimulus intensity

 

What is the minimal, or threshold stimulus?

 

What is the maximal stimulus?

 

How can you explain the increase in force that you observe?

 

 

What type of summation is tshis?

 

 

 

 

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?  Why or why not?

 

 

 

 

 

Activity 4: Treppe

What do you observe?

 

What happens to force production with each subsequent stimulus?

 

 

 

 

 

 

Activity 5: Summation

What is the active force of the contraction? _____ gms

 

 

What is the active force now?  ______ gms

 

Was there any change in the force generated by the muscle?

 

 

Was there any change in the force generated by the muscle?

 

 

Why has the force changed?

 

 

Do you see the same pattern of changes in the force generated?

 

 

Does the force generated change with each additional stimulus?  If so, how?

 

 

 

 

 

Activity 6:  Fuse frequency- Tetanus

What begins to happen at around 80 msec?

 

 

What is this condition called?

 

 

How does the trace at 130 stimuli/sec compare with the trace at 50 stimuli/sec?

 

 

What is this condition called?

 

 

At what stimulus frequency is there no further increase in force?

 

 

 

What is this stimulus frequency called?

 

 

Activity 7: Fatigue

In fatigue, what happens to force production over time?

 

 

Activity 8: Isometric Contractions

Looking at this graph, what muscle lengths generated the most active force?  (provide a range)

 

________ to ______ mm

 

At what muscle length does passive force begin to play less of a role in the total force generated by the muscle?  ______ mm

 

Looking at this graph, at what muscle length does Passive Force begin to play a role in the total force generated by the muscle?  _______  mm

 

The graph shows a dip at muscle length = 90 mm.  Why is this?

 

 

 

 

What is the key variable in an isometric contraction?

 

 

 

Activity 8, 9: Isometric and Isotonic Contractions

How much time does it take for the muscle to generate 0.5 grams of force?  ______ msec

 

At what point in the trace does the muscle shorten?

 

 

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?

 

 

 

Did it take any longer for the muscle to reach the force it needed to move the weight?

 

 

How does this trace differ from the trace you generated with the 0.5 g weight attached?

 

 

At what weight was the velocity of contraction the fastest?  ______ g

 

What happened when you attached the 2.0 g weight to the muscle and stimulated the muscle?  How did this trace differ from the other traces?  What kind of contraction did you observe?

 

 

 

 

What kind of a trace did you get?

 

What was the force of the contraction?  ________ g

 

Describe your four tracings and explain what has happened in each of them.

 

 

 

 

 

What muscle length(s) generate the fastest contraction velocity?