Muscle Contraction

I think I am having a muscle contraction because I am outside exercising. But what are the steps of a muscle contraction? I am here to tell you.

First: Depolarisation and Calcium Ion Release: The muscle is relaxed and when it contracts here is what happens. An action potential from a motor neuron triggers the release of acetylcholine into the motor end plate which initiates depolarisation within the sarcolemma. Depolarisation causes the sarcoplasmic reticulum to release the stored calcium ions (Ca2+).

Sliding Mechanism and Shortening: When ATP binds to the myosin head the cross-bridge between actin and myosin breaks. The myosin heads change position and swivel, which helps them move to the next binding site. At the new actin site, they return to their original conformation, where it drags the actin along the myosin by a sliding mechanism.

This repeats as the myosin heads drags the actin filaments along the length of the myosin. As actin filaments are anchored to Z lines, and the dragging of actin pulls the Z disc closer together which shortens the sarcomere. Since the sarcomere shortens, the muscle fibres as a whole makes the muscle contract.

Second: Actin and Myosin Cross-Bridge Formation: The binding sites for the myosin heads are covered by a blocking complex (troponin and tropomyosin) on actin. Then the calcium ions bind to troponin, exposing the binding sites for the myosin heads when it is reconfigured. After, the myosin heads then form a cross-bridge with the actin filaments.

I think I am having a muscle contraction because I am outside exercising. But what are the steps of a muscle contraction? I am here to tell you.

First: Depolarisation and Calcium Ion Release: The muscle is relaxed and when it contracts here is what happens. An action potential from a motor neuron triggers the release of acetylcholine into the motor end plate which initiates depolarisation within the sarcolemma. Depolarisation causes the sarcoplasmic reticulum to release the stored calcium ions (Ca2+).

Sliding Mechanism and Shortening: When ATP binds to the myosin head the cross-bridge between actin and myosin breaks. The myosin heads change position and swivel, which helps them move to the next binding site. At the new actin site, they return to their original conformation, where it drags the actin along the myosin by a sliding mechanism.

This repeats as the myosin heads drags the actin filaments along the length of the myosin. As actin filaments are anchored to Z lines, and the dragging of actin pulls the Z disc closer together which shortens the sarcomere. Since the sarcomere shortens, the muscle fibres as a whole makes the muscle contract.

Second: Actin and Myosin Cross-Bridge Formation: The binding sites for the myosin heads are covered by a blocking complex (troponin and tropomyosin) on actin. Then the calcium ions bind to troponin, exposing the binding sites for the myosin heads when it is reconfigured. After, the myosin heads then form a cross-bridge with the actin filaments.

I think I am having a muscle contraction because I am outside exercising. But what are the steps of a muscle contraction? I am here to tell you.

First: Depolarisation and Calcium Ion Release: The muscle is relaxed and when it contracts here is what happens. An action potential from a motor neuron triggers the release of acetylcholine into the motor end plate which initiates depolarisation within the sarcolemma. Depolarisation causes the sarcoplasmic reticulum to release the stored calcium ions (Ca2+).

Sliding Mechanism and Shortening: When ATP binds to the myosin head the cross-bridge between actin and myosin breaks. The myosin heads change position and swivel, which helps them move to the next binding site. At the new actin site, they return to their original conformation, where it drags the actin along the myosin by a sliding mechanism.

This repeats as the myosin heads drags the actin filaments along the length of the myosin. As actin filaments are anchored to Z lines, and the dragging of actin pulls the Z disc closer together which shortens the sarcomere. Since the sarcomere shortens, the muscle fibres as a whole makes the muscle contract.

Second: Actin and Myosin Cross-Bridge Formation: The binding sites for the myosin heads are covered by a blocking complex (troponin and tropomyosin) on actin. Then the calcium ions bind to troponin, exposing the binding sites for the myosin heads when it is reconfigured. After, the myosin heads then form a cross-bridge with the actin filaments.