Questions: What is a function of transverse tubules? Multiple Choice To transmit action potentials (impulses) into the cell interior To store calcium ions needed for activating tropomyosin To store sodium ions needed to initiate an action potential at the cell surface To connect actin to the myosin filaments

The answer is the first one: To transmit action potentials (impulses) into the cell interior.

Explanation for each option:

• To transmit action potentials (impulses) into the cell interior: This is the correct function of transverse tubules (T-tubules). T-tubules are invaginations of the cell membrane in muscle cells that help propagate action potentials from the surface of the muscle fiber deep into its interior. This ensures that the electrical signal reaches all parts of the muscle fiber simultaneously, leading to a coordinated contraction.

• To store calcium ions needed for activating tropomyosin: This is incorrect. Calcium ions are stored in the sarcoplasmic reticulum, not in the transverse tubules. The release of calcium from the sarcoplasmic reticulum is what activates the muscle contraction process by binding to troponin, which in turn moves tropomyosin away from the actin binding sites.

• To store sodium ions needed to initiate an action potential at the cell surface: This is incorrect. Sodium ions are not stored in the transverse tubules. Instead, they play a role in generating action potentials by flowing into the cell through voltage-gated sodium channels on the cell membrane.

• To connect actin to the myosin filaments: This is incorrect. The connection between actin and myosin filaments is part of the contractile mechanism within the muscle fibers, but it is not a function of the transverse tubules. The T-tubules are involved in transmitting electrical signals, not in the mechanical connection of actin and myosin.

In summary, the primary function of transverse tubules is to transmit action potentials into the cell interior, facilitating the rapid and uniform contraction of muscle fibers.