sarcoplasmic reticulum

Examples of sarcoplasmic reticulum 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.

• 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.

• 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.

• The Endoplasmic Reticulum

  • The endoplasmic reticulum is an organelle that is responsible for the synthesis of lipids and the modification of proteins.
  • The smooth endoplasmic reticulum (SER) is continuous with the RER but has few or no ribosomes on its cytoplasmic surface.
  • 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.
  • This transmission electron micrograph shows the rough endoplasmic reticulum and other organelles in a pancreatic cell.
  • Describe the structure of the endoplasmic reticulum and its role in synthesis and metabolism

• Vertebrate Digestive Systems

  • The four compartments of the stomach are called the rumen, reticulum, omasum, and abomasum.
  • These animals do not have a rumen, but do have an omasum, abomasum, and reticulum.
  • The first two stomachs, the rumen and the reticulum, contain prokaryotes and protists that are able to digest cellulose fiber.
  • The ruminant regurgitates cud from the reticulum, chews it, and swallows it into a third stomach, the omasum, which removes water.

• Characteristics of Eukaryotic Cells

  • numerous membrane-bound organelles (including the endoplasmic reticulum, Golgi apparatus, chloroplasts, and mitochondria)
  • The endoplasmic reticulum modifies proteins and synthesizes lipids, while the golgi apparatus is where the sorting, tagging, packaging, and distribution of lipids and proteins takes place.
  • The nucleus stores chromatin (DNA plus proteins) in a gel-like substance called the nucleoplasm.The nucleolus is a condensed region of chromatin where ribosome synthesis occurs.The boundary of the nucleus is called the nuclear envelope.It consists of two phospholipid bilayers: an outer membrane and an inner membrane.The nuclear membrane is continuous with the endoplasmic reticulum.Nuclear pores allow substances to enter and exit the nucleus.

• The Nucleus and Ribosomes

  • The nuclear membrane is continuous with the endoplasmic reticulum, while nuclear pores allow substances to enter and exit the nucleus.

• Plant Responses to Gravity

  • When amyloplasts settle to the bottom of the gravity-sensing cells in the root or shoot, they physically contact the endoplasmic reticulum (ER).

• Neurons

  • Each neuron has a cell body (or soma) that contains a nucleus, smooth and rough endoplasmic reticulum, Golgi apparatus, mitochondria, and other cellular components.

• Methods of Intracellular Signaling

  • For signaling purposes, Ca2+ is stored in cytoplasmic vesicles, such as the endoplasmic reticulum, or accessed from outside the cell.