Part Two: The Skeletal Muscle Cell Flashcards Preview

A&P I Muscular System Review > Part Two: The Skeletal Muscle Cell > Flashcards

Flashcards in Part Two: The Skeletal Muscle Cell Deck (8)
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Each muscle cell is made up of around 1000 “strings” (cylinders) shown

at "5". What are these called?

Myofibrils Myo=muscle Fibril=thread-like


What is the repeating pattern of lines, shown at "6," called?

The sarcomere is the repeating pattern of lines (made of

proteins) found inside the myofibrils of the muscle cell.


What is the name of a muscle fiber's cell membrane, shown at "7"?



What is the name of the tubes shown at "8"?

Transverse Tubules or T-tubules


What is the purpose of these tubes (8) in helping the muscle to


T-tubules carry the electrical current (called an action

potential) produced by nerves from the surface of the muscle cell

into its interior. This makes sure that all of the myofibrils

inside the cell (all 1000 of them) take part in the contraction.

The myofibrils are “strings” filled with sarcomeres, which are

where the proteins responsible for contraction of the cell are



What structure is shown at “10” in the diagram?

Sarcoplasmic reticulum (SR)


Structure “10” stores a substance needed to start the muscle

contraction. What is this substance and what causes its release?

The SR stores calcium. The release of the SR’s calcium inside

skeletal muscle cells is caused by the electrical currents that

nerves create. These electrical currents enter the muscle cell

(by flowing down T-tubules) and cause the sarcoplasmic reticulum

to release its calcium.


How is structure “10” also important in ending/stopping a muscle


To end a contraction, the calcium in the muscle must be

returned/pumped back into the sarcoplasmic reticulum. If calcium

remains in the muscle, it cannot relax (stays contracted). (This

is because the myosin heads stay attached to actin and cannot

separate). See questions #33 and #34 for more information about

the SR and calcium.