MUSCLE PHYSIOLOGY

Detailed explanation-1: -21.4 Sarcoplasmic Reticulum and its Couplings to the Plasma Membrane. Each myofibril within the cell is surrounded by a network of interconnecting membranous tubules and cisternae, the SR (Figs.

Detailed explanation-2: -Each segment of the sarcoplasmic reticulum forms a cufflike structure surrounding a myofibril, the fine contractile fibres that extend the length of striated muscle cells.

Detailed explanation-3: -In heart muscle cells, most of the calcium is stored inside a chamber named the sarcoplasmic reticulum. The calcium in the sarcoplasmic reticulum is released during heart muscle contraction and transported back inside the sarcoplasmic reticulum during relaxation.

Detailed explanation-4: -The sarcoplasmic reticulum releases calcium ions during muscle contraction and absorb them during relaxation.