1. Describe and explain the following responses of the biceps AND triceps during
ID: 79708 • Letter: 1
Question
1. Describe and explain the following responses of the biceps AND triceps during slow elbow flexion and extension against a load.
a. What are the changes in level of excitation from the starting point to the completion point of the range of motion in the sagittal plane about a transverse axis?
b. What are the differences in the level of excitation between elbow flexion and elbow extension in the sagittal plane about a transverse axis?
c. What would be the differences in the level of excitation between elbow flexion and elbow extension in the transverse plane about a vertical axis?
Explanation / Answer
1)
a)
The movement of biceps and triceps in the sagittal place on transverse axis means that the stretched arm is moved from the front to the rear side to the extent that it can go. As the arm movement started as an extended arm, already the triceps and biceps are in extended state. As these muscles are not in resting state of excitation with the potential difference of -75mV, the excitation state must be in depolarized state. When the muscles are moved horizontally from front to the rear end as much as it can move, the excitation stages of the two muscles remain depolarized equally. In resting potential, more potassium ions and less sodium ions are inside the muscle cells. In depolarization, sodium channels open up and more sodium moves in during flexion and calcium is released from sarcoplasmic reticulum. In extension of the muscle, calcium is sent into the sarcoplasmic reticulum.
b)
As the elbow flexion can be done totally in the front side while it cannot be done totally in the rear side of the body, the excitation levels of the elbow flexion will lead to total depolarization when it is bent to the front. When it is extended towards the rear end, it cannot be flexed to the back and hence the excitatory levels of the muscle cells will remain repolarized. But, to the extent of elbow extension to the maximum, repolarization takes place and continues to exist in that state till the arm is brought back to the resting state.
c)
There will not be much differences between the elbow flexion and extension during their movement in the transverse plane of vertical axis as there is not total flexion or total extension involved in this movement. Eg. Hitting the ball around from the bottom and rotating the arms.
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