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Lecture Eight : Muscle I - Skeletal muscle structure and function

Q: Explain the cellular structure of an individual muscle fibre

Each muscle fibre has hundreds to thousands of nuclei's. A muscle fibre is comprised of bundles of myofibrils. Myofibrils are made of repeating units called sarcomeres. Sarcomeres are made of contractile proteins/myofilaments called Actin (thin) and Myosin (thick) filaments. The organization of these myofilaments give muscle its striated (striped) appearance.

3 important questions on Lecture Eight : Muscle I - Skeletal muscle structure and function

Describe the characteristics of the Skeletal muscle and Explain its functions ?

The skeletal muscle are huge multinucleate fibre cells that contains large amount of proteins.
Consist of connective tissue (tendons) which covers the muscle fibres and connect muscles to bone.
Richly supplied with blood vessels and nerve fibres
Voluntary control, meaning we can control them.

FUNCTIONS :

Primary : Develop tension or force, in one direction.
Secondary : Support and protect soft internal organs.

Explain the cellular structure of an individual muscle fibre

Each muscle fibre has hundreds to thousands of nuclei's.
A muscle fibre is comprised of bundles of myofibrils.
Myofibrils are made of repeating units called sarcomeres.
Sarcomeres are made of contractile proteins/myofilaments called Actin (thin) and Myosin (thick) filaments.
The organization of these myofilaments give muscle its striated (striped) appearance.

Explain the Sliding Filament Theory in Muscle Contraction

The actin and myosin filaments develop force by triggered molecular interaction that allows association of the myosin head with the nearby thin actin filaments followed by the flexing of the myosin head to allow it to "walk" along the thin filament.
During contraction, actin is drawn closer towards each other overlapping the myosin filaments - bringing the z-lines closer together. This causes the sarcomeres to shorten but myofilaments are not.