Question

multiple choice question

which is true of the light bands in skeletal muscle?

they are called i bands and are bisected by a z disc.
they are called m lines and represent the interaction of the myosin filaments and z discs.
they are called a bands and represent the overlap of actin and myosin filaments.
they are called a bands and represent the interaction of the actin filaments and z discs.

Explanation:

Identify the light bands in skeletal muscle

Using the Sarcomere Bands knowledge point, skeletal muscle striations consist of alternating dark and light bands. The light bands are isotropic to polarized light, giving them the name I bands.

Analyze the structure of the I band

Using the Sarcomere Bands and A Band Anatomy knowledge points, the I bands consist primarily of thin actin filaments. Each light I band is bisected in the middle by a dense protein structure known as the Z disc (or Z line), which anchors the thin filaments.

Evaluate the given multiple-choice options

• Option 1 states they are called I bands and are bisected by a Z disc. This is anatomically correct.
• Option 2 is incorrect because M lines are in the center of the dark A bands.
• Options 3 and 4 are incorrect because the dark bands are called A bands, not the light bands.

Answer:

• (A) They are called I bands and are bisected by a Z disc. (Correct answer)
• (B) They are called M lines and represent the interaction of the myosin filaments and Z discs.
• (C) They are called A bands and represent the overlap of actin and myosin filaments.
• (D) They are called A bands and represent the interaction of the actin filaments and Z discs.