Describe in great detail the molecular characteristics of the contractile filaments in the skeletal muscle fiber; explain their interactions during skeletal muscle contractions.
Understand the Problem
The question is asking for a detailed explanation of the molecular structure of contractile filaments (actin and myosin) in skeletal muscle fibers and how these filaments interact during the process of muscle contraction. This involves discussing aspects such as the sliding filament theory, cross-bridge cycling, and the role of ATP in muscle contractions.
Answer
Contractile filaments are thick filaments (myosin) and thin filaments (actin). They interact by sliding past each other during muscle contraction.
The contractile filaments in skeletal muscle fibers are composed of thick filaments mainly made of myosin, and thin filaments mainly made of actin. During muscle contraction, these filaments slide past each other through cross-bridge cycling, where myosin heads bind to actin, pulling the filaments over each other and shortening the sarcomere.
Answer for screen readers
The contractile filaments in skeletal muscle fibers are composed of thick filaments mainly made of myosin, and thin filaments mainly made of actin. During muscle contraction, these filaments slide past each other through cross-bridge cycling, where myosin heads bind to actin, pulling the filaments over each other and shortening the sarcomere.
More Information
Skeletal muscle contraction is regulated by calcium ions, which interact with proteins like troponin and tropomyosin on the thin filament, allowing myosin to bind actin. The energy for cross-bridge cycling comes from ATP, which myosin hydrolyzes to ADP and inorganic phosphate.
Tips
A common mistake is confusing the sliding filament theory with the shortening of the filaments themselves. The filaments do not shorten but slide past each other.
Sources
- Muscle Fiber Contraction and Relaxation | Anatomy and Physiology I - courses.lumenlearning.com
- 15.4: Muscle Contraction - Biology LibreTexts - bio.libretexts.org
- 10.2 Skeletal Muscle – Anatomy & Physiology - open.oregonstate.education
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