Microscopic Muscle Quick Check

Front

When a skeletal muscle fiber contracts, what happens to the light band (I band) within a sarcomere?

Back

Its width decreases noticeably

Front

What are the two molecules required in the sarcomere for contraction to occur? (the two "ingredients" for contraction)

Back

ATP and calcium ions

Front

A motor neuron stops firing. Which molecular sequence best explains how the muscle fiber relaxes?

Back

Calcium leaves troponin and is pumped into the SR; tropomyosin covers up the binding sites; ATP allows myosin to detach

Front

Which immediate cellular change after death most directly causes ATP production to stop in muscle cells?

Back

Loss of oxygen supply to cells

Front

What is the organelle where calcium ions are normally stored in living muscle cells before they are released to trigger contraction?

Back

Sarcoplasmic reticulum (SR)

Front

During the first 12 hours after death, which pattern best describes cytoplasmic ATP and calcium levels in muscle cells?

Back

ATP decreases as calcium increases

Front

Which change helps explain why rigor mortis eventually disappears after about a day?

Back

Enzymatic decomposition breaks down proteins

Front

After death, why do muscle cross-bridges remain attached during rigor mortis?

Back

ATP is absent to detach myosin heads

Front

Which process that normally supplies ATP stops soon after death?

Back

Aerobic cellular respiration in mitochondria

Front

What is the name of structure #2?

Back

Tropomyosin