What is the sliding filament model of contraction?

Answer 1

The sliding filament theory is the basic summary of the process of skeletal muscle contraction. Myosin moves along the filament by repeating a binding and releasing sequence that causes the thick filament to move over the thinner filament. This progresses in sequential stages. By progressing through this sequence the filaments slide and the skeletal muscles contract and release.

First Stage:
The first stage is when the impulse gets to the unit. The impulse travels along the axon and enters the muscle through the neuromuscular junction. This causes full two to regulate and calcium channels in the axon membrane to then open. Calcium ions come from extra cellular fluid and move into the axon terminal causing synaptic vessels to fuse with pre synaptic membranes. This causes the release of acetylcholine (a substance that works as a transmitter) within the synaptic cleft. As acetylcholine is released it defuses across the gap and attaches itself to the receptors along the sarcolemma and spreads along the muscle fiber.

Second Stage:
The second stage is for the impulse spreads along the sarcolemma. The action potential spreads quickly along the sarcolemma once it has been generated. This action continues to move deep inside the muscle fiber down to the T tubules and the action potential triggers the release of calcium ions from the sarcoplasmic reticulum.

Third Stage:
During the third stage calcium is released from the sarcoplasmic reticulum and actin sites are activated. Calcium ions once released begin binding to Troponin. Tropomyosin blocking the binding of actin is what causes the chain of events that lead to muscle contraction. As calcium ions bind to the Troponin it changes shape which removes the blocking action of Tropomyosin (thin strands of protein that are wrapped around the actin filaments). Actin active sites are then exposed and allow myosin heads to attach to the site.

Fourth Stage:
The fourth stage then begins in which myosin heads attach to actin and form cross bridges, ATP is also broken down during this stage. Myosin binds at this point to the exposed binding sites and through the sliding filament mechanism the muscles contract.

Fifth Stage:
During the fifth stage the myosin head pulls the Actin filament and ADP and inorganic Phosphate are released. ATP binding allows the myosin to detach and ATP hydrolysis occurs during this time. This recharges the myosin head and then the series starts over again.

Stage Six:
Cross bridges detach while new ATP molecules are attaching to the myosin head while the myosin head is in the low-energy configuration. Cross bridge detachment occurs while new ATP attaches itself to the myosin head. New ATP attaches itself to the myosin head during this process.

Stage Seven:
During stage seven the ATP is broken down and used as energy for the other areas including new cross bridge formation. Then the final stage (stage 8) begins and a drop in stimulus causes the calcium concentrate and this decreases the muscle relaxation.

Answer 2

The sliding filament theory applies to understanding how muscles contract. The theory was developed independently by Andrew F. Huxley and Rolf Niedergerke and by Hugh Huxley and Jean Hanson in 1954.

Answer 3

The sliding filament model of contraction involves actin and myosin filaments sliding past each other to create muscle contraction. It occurs in a process of four steps:

1. ATP hydrolyzes, energizing the myosin "heads."

2. The myosin heads attach to the binding sites on the actin filaments.

3. A "power stroke" occurs, in which the filaments slide past each other, thus shortening the sarcomere and contracting the muscle.

4. Another ATP binds to the mysin head and it detaches from actin.

This process can repeat granted Ca+2 and ATP are available.

Answer 4

A theory that explains how muscles contract. Each sarcomere(the functional unit of the muscle) contains overlapping thin (see actin) and thick (see myosin) filaments that can be interconnected by cross bridges. According to the theory, a shortening of sarcomere length is brought about by the two types of filaments sliding past each other by means of a ratchet-like mechanism of the cross bridges. Strong intermolecular forces occurring between the myosin head and cross bridge, cause the head to tilt. By means of this so-called power stroke, the thin filaments are pulled into the space between the thick filaments in each sarcomere. Contraction is triggered by a stimulatory nerve-impulsethat causes an action-potentialto spread across the sarcomere. The action potential causes calcium ions to be released around the filaments, enabling the cross bridges from myosin to attach onto the actin (in the absence of calcium, the attachment sites are blocked by tropomyosin. adenosine-triphosphateprovides the energy used by the ratchet mechanism. See also rigor-complex.

Sliding-filament theory