Name: Bone Disorder
Uploaded: 2019-07-19
Duration: 4 min 55 s
Description: Our bones constantly go through wear and tear and also repair. Thus, there is a balance. But with age, this balance sort of deteriorates, resulting in a cond...

Question

Explain the mechanism of muscle contraction.

Accepted Answer

Muscle tissue contains some fibers called muscle fibers, which consist of a single muscle cell. They are made up of actin and myosin. They help to control the physical forces within the body. There are three types of muscle tissues that are divided on the basis of their function.

Skeletal muscle: Attached to the skeleton by tendons and control the voluntary movements of the body.

Smooth muscle: Smooth muscles are involuntary, meaning that you can’t control them. They’re found in your internal organs and eyes.

Cardiac muscle: These are the muscles that are found in the heart.

The most widely accepted theory explaining how muscle fibers contract is called the sliding filament theory. According to this theory, myosin filaments use energy from ATP to “walk” along the actin filaments with their cross bridges. This pulls the actin filaments closer together. The movement of the actin filaments also pulls the Z lines closer together, thus shortening the sarcomere.

There are four types of muscle contraction:

Isometric: A muscular contraction in which the length of the muscle does not change.

Isotonic: A muscular contraction in which the length of the muscle changes.

Eccentric: An isotonic contraction where the muscle lengthens.

Concentric: An isotonic contraction where the muscle shortens.

The following are the biochemical events in the mechanism of muscle contraction :

The active site on actin is exposed as Ca++ binds troponin.

The myosin head forms a cross-bridge with actin.

During the power stroke, the myosin head bends and ADP and phosphate are released.

A new molecule of ATP attaches to the myosin head, causing the cross-bridge to detach.

ATP hydrolyzes to ADP and phosphate which returns the myosin to the cocked position.

FACTORS INFLUENCING MUSCLE CONTRACTION

If it is to stimulate a single motor unit with progressively higher frequencies of action potentials you would observe a gradual increase in the force generated by that muscle. This phenomenon is called ''wave summation''. Eventually, the frequency of action potentials would be so high that there would be no time for the muscle to relax between the successive stimuli, and it would remain totally contracted, a condition called ''tetanus''.

ENERGY SOURCE FOR MUSCLE CONTRACTION

The ultimate source of energy for muscle contraction is ATP, Cytosolic ATP.

Creatine Phosphate.

Glycolysis.

Aerobic or Oxidative Respiration.

Explain the mechanism of muscle contraction.

Important Questions on Musculo-Skeletal System

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