A contraction is defined simply as the generation of tension within a muscle fiber.
Muscle fibers generate tension through actin and myosin cross-bridge cycling.
Under tension, a muscle belly can either lengthen, shorten, or remain the same length..
Muscle contraction occurs when the thin actin and thick myosin filaments slide past each other.
It is generally assumed that this process is driven by cross-bridges which extend from the myosin filaments and cyclically interact with the actin filaments as ATP is hydrolysed..
Muscle contraction is the tightening, shortening, or lengthening of muscles when you do some activity.
It can happen when you hold or pick up something, or when you stretch or exercise with weights..
Muscle contraction occurs when the thin actin and thick myosin filaments slide past each other.
It is generally assumed that this process is driven by cross-bridges which extend from the myosin filaments and cyclically interact with the actin filaments as ATP is hydrolysed..
Muscle contraction takes place by the cyclic interaction of two-stranded helical actin filaments with protuberances from the myosin filaments known as cross-bridges.
The nature of the contractile process demands that the myosin cross-bridge be highly polymorphic..
As organs that contain cells that can contract, muscles can generate force and movement.
Skeletal muscle works in conjunction with the bones of the skeleton to create body movements..
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..
Muscle contraction begins when the nervous system generates a signal.
The signal, an impulse called an action potential, travels through a type of nerve cell called a motor neuron.
The neuromuscular junction is the name of the place where the motor neuron reaches a muscle cell..
To sustain muscle contraction, ATP needs to be regenerated at a rate complementary to ATP demand.
Three energy systems function to replenish ATP in muscle: (.
1) Phosphagen, (.
2) Glycolytic, and (.
3) Mitochondrial Respiration..
Skeletal muscle is attached to bone through tendons and it contracts or relaxes in order to move the bone that it is connected to.
Muscles can work in antagonistic pairs so that when one muscle contracts, the other relaxes..
The termination of muscle contraction is followed by muscle relaxation, which is a return of the muscle fibers to their low tension-generating state. For the contractions to happen, the muscle cells must rely on the interaction of two types of filaments:
The contractile activity of smooth muscle cells can be tonic (sustained) or phasic (transient) and is influenced by multiple inputs such as:
According to this theory, muscle contraction is a cycle of molecular events in which thick myosin filaments repeatedly attach to and pull on thin actin filaments, so they slide over one another.
The actin filaments are attached to Z discs, each of which marks the end of a sarcomere.
In other words, the “excitation” step in skeletal muscles is always triggered by signaling from the nervous system.
Once the muscle fiber is stimulated by the motor neuron, actin, and myosin protein filaments within the skeletal muscle fiber slide past each other to produce a contraction.
Muscles without one-to-one relationship between electrical stimulation and mechanical contraction
