In mammalian skeletal muscle, the transverse tubules invaginate from the sarcolemma at a characteristic position within each sarcomere. Where are they located?

• A At the level of the Z line
• B Along the M line
• C Within the H zone
• D At the junction of the A and I bands ✓

Explanation

In skeletal muscle each T tubule lies at the A-I junction, flanked on both sides by terminal cisternae of the sarcoplasmic reticulum to form a triad, placing the voltage sensors close to the calcium release channels. In cardiac muscle the T tubules sit at the Z line and form dyads with only one cisterna. This anatomical difference is a standard comparison point between the two muscle types.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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