ANATOMY

Detailed explanation-1: -Each myofibril is surrounded by the sarcoplasmic reticulum, which is closely associated with the transverse tubules. The sarcoplasmic reticulum acts as a sink of Ca+ ions, which are released upon signalling from the transverse tubules.

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: -Myofibrils are composed of 2 types of myofilaments: thick and thin. In skeletal muscle, these myofilaments are arranged in a very regular, precise pattern: thick myofilaments are typically surrounded by 6 thin myofilaments (end view).

Detailed explanation-4: -The sarcoplasmic reticulum is a complex network of specialized smooth endoplasmic reticulum that is important in transmitting the electrical impulse as well as in the storage of calcium ions. These longitudinal tubules form a membrane-bound system of tubules and cisterns that surround the myocytes.

Detailed explanation-5: -The sarcoplasmic reticulum of the muscle fibers stores calcium ions. Myofilaments or myofibrils are parallelly arranged filaments present in the sarcoplasm having alternate dark and light bands. Myofibrils have striated appearance due to the distribution of two important proteins – Actin and Myosin.