Sliding Filament Theory
Explains muscle contraction as the sliding of thin (actin) filaments over thick (myosin) filaments.
What is Sliding Filament Theory?
The basic contractile unit of striated muscle, extending from one Z-line to the next.
Key points
- Explain the mechanism of muscle contraction based on the Sliding Filament Theory.
- Identify the roles of actin, myosin, ATP, and calcium ions in muscle contraction.
- Describe the changes in the sarcomere during contraction.
- Understand the cross-bridge cycle and its energy requirements.
Common exam trap
Believing that filaments shorten during contraction.
Definitions
- Term
Sarcomere
- Meaning
The basic contractile unit of striated muscle, extending from one Z-line to the next.
- Term
Actin Filament
- Meaning
The thin filament of muscle, composed primarily of actin protein, along with troponin and tropomyosin.
- Term
Myosin Filament
- Meaning
The thick filament of muscle, composed primarily of myosin protein, which has cross-bridges (heads) capable of interacting with actin.
- Term
Cross-bridge Cycle
- Meaning
The cyclical series of events involving the binding of myosin heads to actin, the power stroke, detachment, and reactivation of the myosin head, which drives muscle contraction.
Learning objectives
Explain the mechanism of muscle contraction based on the Sliding Filament Theory.
Identify the roles of actin, myosin, ATP, and calcium ions in muscle contraction.
Describe the changes in the sarcomere during contraction.
Understand the cross-bridge cycle and its energy requirements.
Prerequisites
Structure of a sarcomere (Z-lines, A-band, I-band, H-zone)
Proteins involved in muscle contraction (actin, myosin, troponin, tropomyosin)
Role of ATP and calcium ions in cellular processes
Common mistakes
Believing that filaments shorten during contraction.
Confusing the roles of actin and myosin.
Forgetting the role of calcium ions and troponin-tropomyosin complex.
Not understanding the cyclical nature of the cross-bridge interaction.
Misinterpreting changes in the A-band, I-band, and H-zone.
Keywords
Sliding Filament Theory
Muscle Contraction
Sarcomere
Actin
Myosin
ATP
Calcium Ions
Troponin
Tropomyosin
Cross-bridge Cycle
Z-lines
A-band
I-band
H-zone
Practice preview
Which of the following bands or zones shorten during muscle contraction according to the Sliding Filament Theory?…
easy
In a relaxed muscle, the Z-lines are farthest apart. During contraction, the Z-lines move:…
easy
The cross-bridge cycle, essential for muscle contraction as described by the Sliding Filament Theory, involves the interaction between:…
medium