Muscle Fiber and Sarcomere

Front

What is a fascicle?

Back

A fascicle is a bundle of muscle fibers (cells) surrounded by a connective tissue sheath.

Front

What is a muscle fiber?

Back

A muscle fiber is a single muscle cell that is capable of contraction.

Front

What is a myofibril?

Back

A myofibril is a long, thread-like structure within a muscle fiber that contains the contractile proteins.

Front

What is a sarcomere?

Back

A sarcomere is the basic functional unit of a muscle fiber, defined as the segment between two Z lines.

Front

What are myofilaments?

Back

Myofilaments are the filaments of myofibrils, composed mainly of actin and myosin, responsible for muscle contraction.

Front

What is actin?

Back

Actin is a thin filament protein that plays a key role in muscle contraction.

Front

What is myosin?

Back

Myosin is a thick filament protein that interacts with actin to produce muscle contraction.

Front

What is the role of troponin in muscle contraction?

Back

Troponin is a protein that binds to calcium ions and helps regulate muscle contraction by moving tropomyosin away from actin binding sites.

Front

What is the role of tropomyosin in muscle contraction?

Back

Tropomyosin is a protein that blocks the binding sites on actin filaments, preventing contraction until calcium ions bind to troponin.

Front

What is the sarcolemma?

Back

The sarcolemma is the cell membrane surrounding a muscle fiber.