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The popular model of muscle contraction is "Sliding filament hypothesis" which is proposed by A.F.Huxely and H.E. Huxely.
According to this hypothesis filaments of myofibrils (actin and myosin) slide over each other for the contraction. Muscle cells are not compressed or stretched.
Calcium ions are released from sarcoplasmic reticulum causing re-orientation in actin filament. This enables it to bind to the myosin extensions (known as globular heads or cross bridges).
The myosin filament binds and splits an ATP molecule. As the result the myosin head binds to the actin filament further ahead.
The globular head moves (bends) and the actin filament attached to it also moves and overlaps the myosin filament.
Because of this the actin and myosin filament occupy less space when their overlap is maximum. At this stage the sarcomere (containing unit of myofibrils) is contracted thus the muscle contraction occurs.
As long as the sarcoplasmic reticulum provides the ATP and calsium ions, the myosin can crawl along the actin and muscle contractions continue.
The enzyme ATPase breaks down ATP into ADP to provide energy for muscle contraction. The energy is stored in form of glycogen in muscles which is converted into glucose and then into ATP when muscles contract.
During intensive muscle activity phosphocreatin is broken down into creatin and phosphate group. This phosphate group then combines with ADP to form ATP.
animation will help you in understanding muscle contraction. see the related link below
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∙ 12y ago
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What does a muscle become when it contracts?
A muscle becomes shorter when it contracts.
When a muscle contracts how does its form change?
A muscle that contracts shortens whereas a muscle that relaxes lengthens.
When one muscle contracts what happens to the opposing muscle?
When one muscle in a pair contracts the other expands.
When muscle contracts it is?
Flexion
When the muscle contracts it is?
Flexion
When a muscle contracts it?
shortens
When a muscle contracts?
shortens
Which muscles contracts when the leg is extended at the knee?
The muscle that contracts when the leg is extended at the knee is call the gastrocnemius muscle
What happens when the biceps muscle contracts?
When the bicep contracts the triceps relax
When one muscle contracts what dose the other muscle do?
Relaxes
When a muscle contracts how does actin and myosin get shorter?
When the muscle contracts, it gets shorter. When it relaxes, it gets longer.
What is the intersection of the muscle?
The site that undergoes most of the movement when a muscle contracts.
