How does a muscle shorten during its contraction and return to its original form during relaxation?
The muscle shortens during its contraction and returns to its original form during relaxation by the following steps:
i) The neurotransmitter acetylcholine is released when a neural signal reaches the neuromuscular junction and acetylcholine creates an action potential in the sarcolemma.
ii) A release of calcium ions occurs due to the action potential, which is spread through the muscle fibres.
iii) The increase in the calcium ion concentration causes the binding of the calcium ion to a sub-unit of troponin on the actin filaments. This causes the removal of active sites in myosin.
iv) The myosin head binds with the exposed active sites of actin and forms a cross-bridge.
v) This causes the attached actin filaments to move towards the centre of A-band.
vi) The Z-line also moves inwards, and a contraction of the sarcomere occurs in the muscles.
vii) During the muscle contraction, the I-band gets reduced while the A-band retains its original length.
viii) Breaking of cross-bridge occurs when the ADP and Pi releasing myosin goes back to its relaxed state and another new ATP binds which breaks the cross-bridge.
ix) Further sliding occurs when the ATP is hydrolysed again by myosin head, and repetition of cross-bridge formation and breakage occurs.
x) This process continues as the calcium ion concentration causes the formation of an action potential.
The above diagram represents the various stages involved in the cross bridge formation, sliding of filaments and breaking of the cross bridge. These processes occur during muscle shortening during its contraction and returning to its original state during relaxation.
Rate this question :
How does a muscle shorten during its contraction and return to its original form during relaxation?Biology - Exemplar
Rahul exercises regularly by visiting a gymnasium. Of late he is gaining weight. What could be the reason? Choose the correct answer and elaborate.
a. Rahul has gained weight due to accumulation of fats in body.
b. Rahul has gained weight due to increased muscle and less of fat.
c. Rahul has gained weight because his muscle shape has improved.
d. Rahul has gained weight because he is accumulating water in the body.
Biology - Exemplar
Calcium ion concentration in blood affects muscle contraction. Does it lead to tetany in certain cases? How will you correlate fluctuation in blood calcium with tetany?Biology - Exemplar
Sarcolemma, sarcoplasm and sarcoplasmic reticulum refer to a particular type of cell in our body. Which is this cell and to what parts of that cell do these names refer to?Biology - Exemplar
Which one of the following statement is incorrect?Biology - Exemplar
Muscles with characteristic striations and involuntary areBiology - Exemplar
Discuss the role of Ca2+ ions in muscle contraction. Draw neat sketches to illustrate your answer.Biology - Exemplar
Match the following and mark the correct option
Biology - Exemplar