Question

multiple choice question

which structures coordinate contraction in cardiac muscle cells?

gap junctions
dense bodies
z lines
striations

Explanation:

Identify the function of gap junctions

Using the Cardiac Muscle Characteristics knowledge point

• Gap junctions are specialized intercellular connections found within the intercalated discs of cardiac muscle tissue.
• They form channels that allow ions to pass directly from the sarcoplasm of one cardiac muscle cell to the next.
• This direct electrical coupling enables rapid propagation of action potentials across the myocardium, coordinating synchronous contraction.

Evaluate alternative options

• Dense bodies: These are anchoring sites for thin filaments in smooth muscle cells, not cardiac muscle cells.
• Z lines: These define the boundaries of sarcomeres in striated muscle (skeletal and cardiac) and anchor thin filaments, but they do not coordinate contraction between cells.
• Striations: These are the alternating light and dark bands visible under a microscope due to the organized arrangement of sarcomeres, representing structural organization rather than a coordinating mechanism.

Answer:

• Gap junctions (Correct answer)
• Dense bodies
• Z lines
• Striations