In cardiac muscles, T-tubules are present
at?
a) Z lines
b) A lines
c) I lines
d) A-I junction
Correct Answer - A
Ans. A. “Z” lines.
[Ref Principles of medical physiology p.794]
The cardiac muscle cell contains actin, myosin the sarcotubular
system and other organelles seen in skeletal muscles.
However, the T system of cardiac muscle is located at Z lines rather
than at A-I junction, where it is located in skeletal muscles.