In eukaryotic muscle cells, the transverse tubules (T-tubules) are located between which structures called cisternae?

• A. Nuclear envelope
• B. Mitochondrial cristae
• C. Golgi cisternae
• D. Terminal cisternae of the sarcoplasmic reticulum

Answer: (D)

Verified step by step guidance

1. Understand the anatomy of a muscle cell: Muscle cells, also known as muscle fibers, are specialized eukaryotic cells that contain structures like the sarcoplasmic reticulum, transverse tubules (T-tubules), and terminal cisternae. These structures work together to facilitate muscle contraction.
2. Learn the role of T-tubules: T-tubules are invaginations of the sarcolemma (the cell membrane of muscle cells) that penetrate into the cell's interior. They help propagate action potentials deep into the muscle fiber, ensuring uniform contraction.
3. Understand the sarcoplasmic reticulum: The sarcoplasmic reticulum is a specialized form of endoplasmic reticulum in muscle cells. It stores calcium ions, which are essential for muscle contraction. The terminal cisternae are enlarged areas of the sarcoplasmic reticulum that are located near the T-tubules.
4. Recognize the relationship between T-tubules and terminal cisternae: T-tubules are situated between two terminal cisternae, forming a structure known as a triad. This triad is critical for the excitation-contraction coupling process, where electrical signals trigger calcium release for muscle contraction.
5. Conclude the correct answer: Based on the anatomy and function of muscle cells, the transverse tubules (T-tubules) are located between the terminal cisternae of the sarcoplasmic reticulum, not the nuclear envelope, mitochondrial cristae, or Golgi cisternae.