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Muscle fiber contraction is a complex process involving a number of cell parts and chemical substances that result in the sliding movement of the actin and myosin filaments and causes a contraction. A myosin filament is composed of protein strands with globular ends called cross-bridges that extend outward along the length of the filament. The actin filaments have ADP molecules attached to its surface that serve as active sites for linking the cross-bridges of the myosin filaments.
Although the process is not completely understood, the sliding filament theory suggests that the myosin cross-bridge attaches to an actin active site and bends slightly, pulling the actin with it. It releases its attachment, straightens, and combines with another active site further down the actin filament, causing the sarcomere to shorten.
When the nerve impulse reaches the distal end of its branch, acetylcholine is released into the gap. The acetylcholine diffuses rapidly across the motor end plate and combines with protein receptors in the sarcolemma. This causes a muscle impulse to be generated and pass in all directions over the entire sarcolemma, and through the T-tubules deep into the fiber. The S.R., which contains a high concentration of calcium ions, becomes more permeable and allows the ions to diffuse into the sarcoplasm. When a high enough concentration is present in the sarcoplasm, the linkages between the actin and myosin filaments occur and contraction takes place. The calcium ions are moved quickly back into the S.R. by an active transport system (calcium pump). When enough calcium ions have been removed from the sarcoplasm, the muscle relaxes. At the same time, the acetylcholine is rapidly decomposed by the enzyme cholinesterase. This prevents a single nerve impulse from causing a sustained contraction.
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What are the units of contraction within a muscle fiber called?
The units of contraction within a muscle fiber are called sarcomeres. Sarcomeres are the basic functional and structural units of striated muscle tissue, composed of actin and myosin filaments. They are organized in a repeating pattern along the length of the muscle fiber, allowing for coordinated contraction and relaxation during muscle activity.
What is a twitch contraction?
A twitch contraction is a single, brief contraction of a muscle fiber in response to a stimulus. It is the smallest unit of muscle contraction and is not strong enough to produce movement of a limb.
What are the structures within the muscle fiber that shorten to cause skeletal muscle fiber contraction?
The structures within the muscle fiber that shorten to cause skeletal muscle contraction are called myofibrils. Myofibrils are composed of repeating units called sarcomeres, which contain thick and thin filaments made of proteins (actin and myosin). When the muscle fiber is stimulated by a nerve impulse, the myosin heads interact with the actin filaments to generate the force required for muscle contraction.
Chemical released to stimulate muscle contraction?
Acetylcholine is the primary neurotransmitter released by motor neurons at the neuromuscular junction to stimulate muscle contraction. It binds to receptors on the muscle cell membrane, initiating a series of events that ultimately lead to muscle contraction.
The narrow space between the synaptic terminal and the muscle fiber is the?
synaptic cleft, where neurotransmitters are released by the synaptic terminal and bind to receptors on the muscle fiber to trigger a muscle contraction.
What best describes the events of excitation in excitation-contraction coupling?
cross bridge formation "Excitation-contraction coupling" connects muscle fiber excitation to the muscle fiber contraction (cross bridge formation). During contraction, myosin heads form cross bridges many times-with each cross bridge generating a small amount of tension in the muscle fiber.
What do you call a shortening of muscle fiber?
contraction
What are the units of contraction within a muscle fiber called?
The units of contraction within a muscle fiber are called sarcomeres. Sarcomeres are the basic functional and structural units of striated muscle tissue, composed of actin and myosin filaments. They are organized in a repeating pattern along the length of the muscle fiber, allowing for coordinated contraction and relaxation during muscle activity.
What is shortening of a muscle fiber called?
a contraction human avatommy
What describes the events of contraction in excitation-contraction coupling?
cross bridge formation "Excitation-contraction coupling" connects muscle fiber excitation to the muscle fiber contraction (cross bridge formation). During contraction, myosin heads form cross bridges many times-with each cross bridge generating a small amount of tension in the muscle fiber.
What is a twitch contraction?
A twitch contraction is a single, brief contraction of a muscle fiber in response to a stimulus. It is the smallest unit of muscle contraction and is not strong enough to produce movement of a limb.
What are the structures within the muscle fiber that shorten to cause skeletal muscle fiber contraction?
The structures within the muscle fiber that shorten to cause skeletal muscle contraction are called myofibrils. Myofibrils are composed of repeating units called sarcomeres, which contain thick and thin filaments made of proteins (actin and myosin). When the muscle fiber is stimulated by a nerve impulse, the myosin heads interact with the actin filaments to generate the force required for muscle contraction.
What does contraction mean in medical terms?
contract or "contraction" is when a muscle fiber lengthens or shortens
The energy source that is directly responsible for muscle fiber contraction is?
ATP
What allows recoil of the muscle fiber when contraction ends?
Elastic filaments
What is the function of cytoplasmic reticulum in the muscle fiber?
increases calcium influx in the muscle fibre, causing contraction.
The contractility of heart muscle is its?
contraction strength at any given fiber length
