SKELETAL MUSCLE PHYSIOLOGY PHYSIOEX 8.0 act. 8&9

Investigating Isometric Contraction

8-1: What happens to the passive and active forces as the muscle length is increased from 50 mm to 100 mm? Specifically, discuss what the force looks like at particular lengths - at what lengths did the force show large increases or decreases.
Passive force: Passive force starts to increase when the length reaches 80mm and never decreases after that.
Active force: Active force increases until the length reaches 74 and it decreases when the length reaches 78mm.
Total force: Total force increases until the length reaches 74mm and starts to decrease when the length reaches 78.

8-2: Explain the dip in the total force curve. (Hint: Keep in mind you are measuring the sum of active and passive forces).The total force is when you ass the active and passive forces together. If the active force decreases so will the total force. The total force would have stayed the same numbers as the active force but the passive force started to increase at the end.


Investigating the Effect of Load on Skeletal Muscle

9-1: What do you see happening to the muscle during the flat part of the tracing? Click "Stimulate" to repeat if you wish to see the muscle action again. What I see happen to the muscle during the flat part is that the muscle is resting.

9-2: Does the force the muscle produces change during the flat part of the tracing. The force stays the same during the flat part of the tracing.

9-3: Which of the two weights used so far results in the highest initial velocity of shortening?
Weight 0.5g is the weight with the highest velocity of 3.77mm/sec.

9-4: Repeat step 6 for the remaining two weights:
Weight 1.00g
Velocity 1.34 mm/sec

Weight 2.00g
Velocity 0.00mm/sec

9-5: What does the plot reveal about the relationship between resistance and the initial velocity of shortening? Increased resistance causes shorter initial velocity of shortening.

9-6: Describe the relationship between starting length and initial velocity of shortening. The velocity of shortening increases at first until 75mm, then it starts to decrease until it reaches 0.00 velocity at 90mm.