How Does Muscle Contraction Occur?
Muscle contraction is a physiological process where muscle fibers generate tension and exert a force, resulting in movement or the stabilization of body parts.
- Muscle contraction begins with a signal from the central nervous system through a motor neuron.
- The neuromuscular junction connects the motor neuron to the sarcolemma.
- Acetylcholine is released at the neuromuscular junction. It results in the action potential in the sarcolemma.
- An action potential triggers the release of calcium ions from the sarcoplasmic reticulum into the sarcoplasm.
- Calcium ions bind to troponin on actin filaments. It exposes the myosin-binding sites.
- Myosin binds to the exposed active sites on actin and forms the cross bridges.
- The hydrolysis of ATP at the myosin head causes sliding of thin filaments over thick filaments.
- As thin filaments slide, the Z lines are pulled closer together. It leads to muscle contraction.
- The cycle of cross-bridge formation, contraction, and sliding repeats until calcium ions are actively pumped back into the sarcoplasmic reticulum.
- With decreasing calcium levels, troponin covers the myosin-binding sites on actin, allowing for muscle relaxation.
- Recurrent muscle activation may lead to the accumulation of lactic acid, contributing to muscular fatigue.
- Myoglobin, a pigment in muscles, contributes to their red color. Muscles rich in myoglobin are adapted for sustained, aerobic activities.
- Red fibers with myoglobin-rich content also have a large number of mitochondria, supporting energy production during prolonged activities.
- Muscles lacking myoglobin appear white and are associated with anaerobic, short cycle of activity.
- As calcium is pumped back, the Z lines return to their initial positions, and the muscle returns to a relaxed state.
Sliding Filament Theory
The sliding filament theory explains how muscle fibres contract. The sliding filament theory can be best explained as how muscles contract by the interaction of actin and myosin filaments sliding past each other within muscle cells. The process requires ATP for energy.
The sliding filament theory was proposed in 1954 by Andrew Huxley and Rolf Niedergerke. In this article, we will study the sliding filament theory of muscle contraction notes in detail.
Table of Content
- What is Sliding Filament Theory?
- What is Sarcomere in Muscle?
- Sliding Filament Theory of Muscle Contraction
- Sliding Filament Theory Diagram
- Summary of the Sliding Filament Theory Steps
- How Does Muscle Contraction Occur?
- Importance of Sliding Filament Theory
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