Muscle Fibers and Their Functions

These flashcards cover the basic characteristics of muscle fibers, their components, and functions relevant for understanding muscular anatomy and physiology.

What is the difference between elasticity and extensibility in skeletal muscle?

Elasticity refers to the ability to return to the original shape after being stretched, while extensibility is the ability to be stretched or extended.

How does skeletal muscle compare to ligaments in terms of elasticity and extensibility?

Skeletal muscle is both elastic and extensible, whereas ligaments are not designed to be extensible.

What are the roles of muscle and ligaments?

Muscle allows for contraction and relaxation, while ligaments hold structures in place and develop tension when pulled.

What do the terms sarco- and myo- signify?

They denote components that are unique to muscle, such as myofilaments and sarcoplasm.

How are muscle cells related to myofibrils?

Muscle cells contain myofibrils that make up the majority of the cell's volume and contribute to muscle contraction.

What is the 'cylinders within cylinders' organization in muscle cells?

Muscle cells have a cylindrical shape, with myofibrils arranged in bundles of cylinders.

What is the role of the epimysium, perimysium, and endomysium?

The epimysium wraps around the entire muscle, the perimysium surrounds fascicles, and the endomysium surrounds individual muscle fibers.

What are T-tubules and what is their function?

T-tubules conduct action potentials and affect terminal cisterns in the sarcoplasmic reticulum during muscle contraction.

What ions are released from terminal cisterns and what is their effect?

Calcium ions are released from terminal cisterns, which bind to proteins in thin filaments to initiate muscle contraction.

What is a triad in muscle cells?

A triad consists of two terminal cisterns adjacent to a T-tubule.

What is the basic structure of thin filaments?

Thin filaments are primarily made of actin and have binding sites for myosin heads.

What triggers contraction in muscle fibers?

The sudden rise in calcium concentration links electrical excitation to the initiation of contraction.

What proteins are involved in the thick filaments?

Thick filaments consist mainly of myosin, which has a globular head and tail.

What structural role does titin play in muscle contraction?

Titin centers thick filaments in the sarcomere, maintaining alignment and providing elasticity.

How does calcium interact with troponin during muscle contraction?

Calcium binds to troponin, causing a conformational change that shifts tropomyosin and exposes binding sites on actin.