Question

question 3
a sarcomere extends from:
a the m line to the next m line
b one z disk to an adjacent z disk
c one t tubule to the next t tubule
d the h zone to the i band
e the middle of the i band to the middle of the a band

Explanation:

A sarcomere is the basic unit of striated muscle tissue. It is defined as the region between two adjacent Z - disks. The Z - disk (also known as the Z - line) serves as an anchor point for the thin filaments (actin). When a muscle contracts or relaxes, the sarcomere changes length.

• Option A: The M - line is in the middle of the sarcomere (in the H - zone) and is not the boundary of a sarcomere.
• Option C: T - tubules are invaginations of the cell membrane and are not related to the definition of a sarcomere's boundaries.
• Option D: The H - zone and I - band are regions within the sarcomere, not its boundaries.
• Option E: These are regions within the sarcomere, not the boundaries that define a sarcomere.

Answer:

B. one Z disk to an adjacent Z disk