Question

Describe the important steps in muscle contraction.

Answer 1

Hint: During muscle contraction, the thick filament slides over the fine filament with the aid of using repeated binding and releases myosin alongside the filament. This entire process happens in a sequential manner.

Complete Answer:
Muscle contraction does not always mean muscle shortening because muscle tension can be generated without modifications in length of muscle like when lifting a large book or a dumbbell at the same posture.

The important steps in muscle contraction are given below-
- Muscle contraction is begun with the aid of using alerts that travel along the axon and get to the neuromuscular junction or motor end plate. As a result, acetylcholine is secreted into the synaptic cleft by producing an action potential within the sarcolemma.
- The formation of this action potential releases calcium ions from the sarcoplasmic reticulum within the sarcoplasm.
- The increased calcium ions inside the sarcoplasm cause the activation of actin sites. Calcium ions stick to the troponin on actin filaments and eliminate the tropomyosin, wrapped all over actin filaments. Therefore, active action sites are uncovered and this enables myosin heads to link to this site.
- In this step, the myosin head connects to the uncovered site of actin and developed cross bridges by using energy from ATP hydrolysis. The actin filaments are pulled in so the H-zone reduces. At this phase the contraction of the muscle happens.
- After muscle contraction the myosin head pulls in the actin filament and frees ADP along with inorganic phosphate. ATP molecules bind and separate myosin and the cross bridges are damaged.
- This process of generation and damage of cross bridges continues until there is a drop in the stimulus, which leads to an increase in calcium.

Note: After muscle contraction the myosin head pulls in the actin filament and releases out ADP along with inorganic phosphate. ATP molecules bind and segregate myosin and the cross bridges are damaged and reduce the calcium ions contraction. As a result, covering these filaments causes muscle relaxation.