sarcoplasm

Examples of sarcoplasm in the following topics:

• Regulatory Proteins

  • Troponin, which regulates the tropomyosin, is activated by calcium, which is kept at extremely low concentrations in the sarcoplasm.
  • The concentration of calcium within muscle cells is controlled by the sarcoplasmic reticulum, a unique form of endoplasmic reticulum in the sarcoplasm.
  • Muscle contraction ends when calcium ions are pumped back into the sarcoplasmic reticulum, allowing the muscle cell to relax.
  • The inward flow of calcium from the L-type calcium channels activates ryanodine receptors to release calcium ions from the sarcoplasmic reticulum.
  • Calcium remains in the sarcoplasmic reticulum until released by a stimulus.

• Skeletal Muscle Fibers

  • The sarcoplasm is rich with glycogen and myoglobin, which store the glucose and oxygen required for energy generation, and is almost completely filled with myofibrils, the long fibers composed of myofilaments that facilitate muscle contraction.
  • 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.
  • A skeletal muscle cell is surrounded by a plasma membrane called the sarcolemma with a cytoplasm called the sarcoplasm.

• Excitation–Contraction Coupling

  • A neural signal is the electrical trigger for calcium release from the sarcoplasmic reticulum into the sarcoplasm.
  • The action potential triggers the sarcoplasmic reticulum to release of Ca2+, which activate troponin and stimulate muscle contraction.
  • The sarcoplasmic reticulum is a specialized endoplasmic reticulum found in muscle cells.

• The Endoplasmic Reticulum

  • In muscle cells, a specialized SER called the sarcoplasmic reticulum is responsible for storage of the calcium ions that are needed to trigger the coordinated contractions of the muscle cells.