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Sliding Filament Theory

“The sliding filament theory is the mechanism by which muscles are thought to contract at the cellular level.”

sliding filament theory of muscle contraction

What is Sliding Filament Theory?

Muscles are fibers that cause movement in our body. They also support the functioning of our internal organs. Experts say there are 650 muscles in the human body, skeletal muscles to be exact.

Muscles are specialized tissues with elastic properties, with countless muscle fibers per muscle. Muscle fibers are also made up of thin and short strands called myofibrils. Walking requires muscle contraction. It contracts when tension points within the muscles are activated. This process is described by the sliding filament theory.

The sliding filament theory is a proposed mechanism of muscle contraction with precise strips, actin and myosin fibers that interact resulting in a decrease in muscle fiber length Actin (thin) filaments fused with myosin (thick). filaments) drive cell movement.

Myosin is a protein that transforms ATP (chemical energy) into mechanical energy, thus creating traction and movement. This movement causes muscle contractions and non-muscle cell movements, such as mitosis and meiosis (cell division).

In addition, actin polymerization and actin-myosin interaction are responsible for cell surface movement. Actin bundles contain myosin binding sites that are exposed when troponin binds to calcium ions in the filaments, facilitating the formation of a bridge between actin and myosin.

This process is initiated by ATP to act as an energy source. ATP-myosin molecules are hydrolyzed in the head causing changes in head shape and binding to actin filaments.


The series of basic structural units that form a striated pattern in muscle cells are called sarcomeres are arranged like pillars throughout the muscle tissue. Single muscle cells express thousands of sarcomeres, which are replicated throughout the cell. Changes in the length of internal proteins can change the length of the muscle, resulting in general changes.

The sarcomere contains many myofibrils – bundles of actin and myosin filaments. Skeletal muscles cause voluntary movement. Sarcomeres in skeletal muscle initiate this movement by contraction that triggers its structure.

Key Points For Sliding Filament Theory

  1. Slip fiber contraction occurs in the sarcomere region.
  2. Myosin fibers scrape against actin filaments when they contact sarcomeres.
  3. Within the sarcomere, bands I and H contract and expand to facilitate movement.
  4. Muscles do not expand or contract on their own.


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