Muscle Physiology 3 - Sarcomere Histology

Front

What are myosin heads?

Back

Myosin heads are the projections on the thick filament (myosin) that interact with actin during muscle contraction.

Front

What is the composition of the thick myofilament?

Back

The thick myofilament is primarily composed of myosin.

Front

What does the H-Zone represent in a sarcomere?

Back

The H-Zone is the region in the center of the sarcomere where only thick filaments (myosin) are present, and it appears lighter under a microscope.

Front

What is tropomyosin?

Back

Tropomyosin is a protein that wraps around actin filaments and helps regulate muscle contraction by blocking the binding sites for myosin heads.

Front

What is troponin?

Back

Troponin is a protein complex that binds to tropomyosin and actin, and it plays a crucial role in muscle contraction by regulating the interaction between actin and myosin.

Front

Define a sarcomere.

Back

A sarcomere is the basic contractile unit of muscle tissue, defined as the segment between two Z lines.

Front

What is the Z line?

Back

The Z line is a structure that defines the boundaries of a sarcomere and anchors the thin filaments (actin).

Front

What is the A band in a sarcomere?

Back

The A band is the dark band in a sarcomere that contains the entire length of the thick filaments (myosin) and overlaps with thin filaments (actin).

Front

What is the I band in a sarcomere?

Back

The I band is the light band in a sarcomere that contains only thin filaments (actin) and is located on either side of the A band.

Front

What is the role of calcium ions in muscle contraction?

Back

Calcium ions bind to troponin, causing a conformational change that moves tropomyosin away from the binding sites on actin, allowing myosin heads to attach and initiate contraction.