Match the following terms with the correct definition.      


____Z-disc     
____Sarcomere     
____A band     
____H zone     
____I band     
____M line


a. The dark band containing the entire length of the thick filament
b. The band of proteins in the middle of the H zone
c. The boundary between sarcomeres
d. The functional unit of contraction
e. The middle region of the A band containing only thick filaments
f. The light band containing only thin filaments

Verified step by step guidance

1. Step 1: Understand the terms and their roles in muscle anatomy. These terms are related to the structure of a sarcomere, which is the functional unit of a muscle fiber. A sarcomere is composed of repeating units of thick and thin filaments, and the arrangement of these filaments creates distinct bands and zones.
2. Step 2: Match the term 'Z-disc' with its definition. The Z-disc (or Z-line) is the boundary between sarcomeres, where thin filaments are anchored. This corresponds to definition (c).
3. Step 3: Match the term 'Sarcomere' with its definition. The sarcomere is the functional unit of contraction in a muscle fiber, as it is the smallest unit capable of contracting. This corresponds to definition (d).
4. Step 4: Match the term 'A band' with its definition. The A band is the dark band that contains the entire length of the thick filament, including regions where thick and thin filaments overlap. This corresponds to definition (a).
5. Step 5: Continue matching the remaining terms: 'H zone' is the middle region of the A band containing only thick filaments (e), 'I band' is the light band containing only thin filaments (f), and 'M line' is the band of proteins in the middle of the H zone (b).

Key Concepts

Z-disc

The Z-disc, or Z-line, is a structural component of a sarcomere, which serves as the boundary between adjacent sarcomeres in a muscle fiber. It anchors the thin filaments (actin) and plays a crucial role in the contraction process by maintaining the alignment of the sarcomere during muscle contraction and relaxation.

Sarcomere

The sarcomere is the fundamental unit of muscle contraction, defined as the segment between two Z-discs. It contains overlapping thick (myosin) and thin (actin) filaments, and its contraction is responsible for the shortening of muscle fibers, enabling movement. Understanding the structure of the sarcomere is essential for grasping how muscles function.

A band

The A band is the dark region of the sarcomere that contains the entire length of the thick filaments (myosin) and overlaps with the thin filaments (actin). This band is crucial for muscle contraction, as it represents the area where the force is generated during the sliding filament mechanism. The A band remains constant in length during contraction, while the I band and H zone change.