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21 Cards in this Set

  • Front
  • Back
• What is a muscle fiber?
o Muscle fiber is synonymous with muscle cell. A muscle fiber therefore is a single muscle cell.
• What is the name of the plasma membrane of a muscle fiber?
o Sarcolemma
• What is the sarcolemma?
o The plasma membrane of a muscle fiber
• Muscle fibers contain thousands of tiny invaginations of their sarcolemma. What is the name and purpose of these invaginations?
o The invaginations of the sarcolemma are called T tubules.

o They are open to the outside of the fiber and thus are filled with interstitial fluid.

o T tubules expand the surface area of the sarcolemma and allow for an action potential to excite all parts of the muscle fiber at essentially the same instant.
• What are T tubules?
o T tubules are invagination of the sarcolemma that allow for an action potential to excite all parts of the muscle fiber at essentially the same instant.
• What is the cytoplasm of a muscle fiber called?
o Sarcoplasm
• What is the sarcoplasm?
o The cytoplasm of a muscle fiber.
• What is cytoplasm?
o Everything within the plasma membrane of a cell, including the cytosol, dissolved elements, and organelles.
• What is myoglobin?
o Myoglobin is a red-coloured protein found in sarcoplasm of muscle fibers.

o Myoglobin is similar to hemoglobin in that it binds oxygen and releases it when needed by the cell.
• What is the name of the contractile organelles of a muscle fiber?
o Myofibril
• What are myofibrils?
o Myofibrils are the thread-like contractile organelles of muscle fibers.

o They are long chains of sarcomeres. The sarcomere is the contractile unit of a muscle fiber.
• What is the sarcoplasmic reticulum?
o The sarcoplasmic reticulum, or SR, is an organelle within the muscle fiber.

The SR is a fluid-filled system of sacs that encircles each myofibril.
• What are the names of the dilated end sacs of the sarcoplasmic reticulum?
Terminal cisterns
• What are the terminal cisterns? What is their purpose?
The terminal cisterns are dilated end sacs of the sarcoplasmic reticulum that butt against the T tubule from both sides.

They contain stores of Ca2+ ions that are released into the cytosol
• What is the ratio of thin filaments to thick filaments in the sarcomere?
o 2 thin filaments for every thick filament
• What protein are thin filaments made of?
Actin
What protein are thick filaments made of?
Myosin
How are cardiac fibers connected to one another?
Cardiac fibers connect to neighbouring fibers via intercalated discs.

Intercalated discs contain desmosomes, which hold the fibers together, and gap junctions, which allow muscle action potentials to conduct from one muscle fiber to its neighbour.
What are the two broad categories of cardiac fibers?
Autorhythmic fibers and contractile fibers

The distinction is useful but somewhat artificial because all cardiac myocytes possess the capacity for autorhythmicity and contractility.
What is autorhythmicity?
...
Which are the autorhythmic fibers?
1) The pacemaker cells of the SA and AV nodes

2) The cells of the conductions system, including the bundle of His, the right and left bundle branches, and the Purkinje fibers.