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Practice Quiz Questions Ch. 11 - Muscle Contraction

Yasmin Alexander avatar Yasmin Alexander
4 September 2022
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question
An action potential enters the depths of a muscle fiber by way of __________. (11)
answer
T tubules
question
Which structure do the calcium ions bind to when muscle contraction is initiated? (11)
answer
The troponin molecule
question
Cross-bridges form between the __________ and the __________. (11)
answer
actin filaments; myosin head
question
An action potential introduced at the neuromuscular junction is propagated along the sarcoplasmic reticulum. (11)
answer
False
question
In response to an action potential entering the neuron, calcium ions diffuse from the sarcolemma into the sarcoplasm. (11)
answer
False
question
An action potential causes calcium ions to diffuse from the ________ into the ________.
answer
sarcoplasmic reticulum; sarcoplasm
question
Which of the following best describes the role of Ca2+ in muscle contraction?
answer
It binds to troponin, moving tropomyosin, so that myosin heads can bind to actin.
question
Which of the following is not a filamentous protein?
answer
Actin Myosin Troponin Tropomyosin Toponi
question
An action potential causes depolarization of the T tubule membrane.
answer
True
question
T tubules are invaginations of the sarcolemma of a muscle cell.
answer
True
question
Correct sequence of smooth muscle contraction
answer
An increase in cytosolic calcium binds to calmodulin in the cytosol. This complex binds with myosin light-chain kinase, which uses ATP to phosphorylate myosin cross-bridges, which bind to the actin filaments' active sites, resulting in contraction.
question
Correct sequence for skeletal muscle contraction
answer
An increase in cytosolic calcium binds to troponin, which moves tropomyosin from blocking the active sites on the actin filament, which binds with myosin, forming cross-bridges, resulting in contraction.
question
Smooth muscle and skeletal muscle fibers both have their contractions triggered by calcium ions.
answer
True
question
Both smooth muscle contractions and skeletal muscle contractions involve thin (actin) filaments sliding over the thick (myosin) filaments.
answer
True
question
During contraction of a muscle, calcium ions bind to the __________.
answer
Troponin
question
The bond between the active site on actin and the myosin head is broken when an __________.
answer
ATP molecule binds to the myosin head
question
The sequence of cross-bridge formation and myofilament movement will be repeated as long as calcium ions and ATP are present.
answer
True
question
When cross-bridges form, and the muscle fibers contract, the actin myofilament slides past the myosin myofilament.
answer
True
question
Muscle contractions are initiated by the binding of __________ to __________.
answer
calcium ions, troponin
question
During muscle contractions, cross-bridges form between the _________ and the __________.
answer
myosin heads; actin filaments
question
Which of the following is the site of ATP binding and hydrolysis?
answer
myosin
question
The binding of ATP immeditely initiates the sliding of muscle filaments past one another.
answer
false
question
After cross-bridges form, phosphate is released, followed by ADP.
answer
true
question
The __________ is described as two strands of actin molecules wrapped together.
answer
thin filaments
question
Which of the following happens as actin and myosin filaments slide past each other during muscle contraction?
answer
neither action or myosin shorten
question
Which of the following statements about the "heads" of the myosin molecules is true?
answer
they can attach to different actin sites
question
Each myosin protein has a globular head that extends outward from the myosin filament.
answer
true
question
Unflexing of the myosin head requires ATP.
answer
true