Question

Short/ Long answer type questions.
If a small load is attached to a muscle that is then tetanically stimulated, the muscle will lift the load in an isotonic contraction over a certain distance and then stop shortening and enter a state of isometric contraction, if a heavier load is used, the distance shortened before entering an isometric contraction is shorter. Explain these shortening limits in terms of the sliding filament model of contraction and the length-tension relation.

Answer 1

The muscle fibres during contraction may lengthen, shorten, or remain the same thereby generating tension with the help of motor neurons. Isotonic contractions maintain constant tension in the muscle as the muscle changes length. This can occur only when a muscle’s maximal force of contraction exceeds the total load on the muscle. However, isometric contractions generate force without changing the length of the muscle which is commonly observed in muscles of hands and forearm as the muscles do not change length, and joints do not move, thus, the force for grip is sufficient and the object does not fall off.