What term describes the swollen chambers of organelles adjacent to T tubules?

The term that describes the swollen chambers of organelles adjacent to T tubules is "cistern." In the context of muscle physiology, particularly skeletal muscle, the cisternae are expansions of the sarcoplasmic reticulum that store calcium ions. These structures are crucial for muscle contraction because the release of calcium from the cisternae into the cytoplasm triggers the contraction process by facilitating the interaction between actin and myosin filaments within the myofibrils.

These swollen chambers are strategically located next to the T tubules, which are invaginations of the muscle fiber's membrane that help transmit the action potential deep into the muscle fiber and facilitate rapid communication between the cell surface and the interior structures, including the cisternae. This proximity allows for an efficient release of calcium in response to electrical signals, essential for muscle contraction.

Other terms listed, such as myofibril, tubule, and sarcoplasm, relate to different components of muscle structure and function. The myofibril refers to the contractile threads within a muscle fiber, the tubule typically refers to structures like the T tubule itself, and sarcoplasm is the cytoplasm of a muscle cell. However, none of these accurately describe the