26 Questions
What is the name of the plasma membrane of a muscle cell?
Sarcolemma
Which element of a muscle cell contains the contractile components?
Myofibrils
What is the name of the dark region in the center of the A band of a sarcomere?
H zone
Which structure anchors the thin filaments at the borders of a sarcomere?
Z lines
What provides the attachment between actin (thin) and myosin (thick) filaments in a muscle cell?
Cross bridges
Which protein uncovers binding sites on actin subunits when bound to calcium?
Troponin
What is the role of titin in muscle contraction?
Anchors the thick filaments in the proper position
What occurs during the power stroke in the cross bridge cycle?
The myosin head pivots toward the middle of the sarcomere and pulls the attached actin filament
What is the role of excitation-contraction coupling in muscle contraction?
Linking the action potential to contraction
What is the main function of tropomyosin in muscle contraction?
Uncovers binding sites on actin subunits
What is the name of the smooth endoplasmic reticulum surrounding the myofibrils in a muscle cell?
Sarcoplasmic reticulum
What is the main function of the Z lines in a sarcomere?
Anchoring of the thin filaments
Which region of the sarcomere appears dark and contains the thick filaments?
A band
What is the role of titin in muscle cells?
Stabilizes the position of myosin filaments within the sarcomere
What provides the attachment between actin (thin) and myosin (thick) filaments in a muscle cell?
Cross bridges
What occurs during the power stroke in the cross bridge cycle?
Release of ADP and inorganic phosphate from myosin
What is the role of the myosin molecule in muscle contraction?
To hydrolyze ATP and detach from actin
Which sequence of events accurately describes the cross bridge cycle in muscle contraction?
Binding of myosin to actin, release of ADP and Pi, attachment of myosin to ATP, hydrolysis of ATP, detachment of myosin from actin
What is the function of the regulatory protein tropomyosin in muscle contraction?
To extend over and cover binding sites on actin subunits
What is the primary role of troponin in muscle contraction?
To release calcium and uncover binding sites on actin
What is the function of the elastic protein titin in muscle contraction?
To provide elasticity and anchor the thick filaments in position
During which phase of the cross bridge cycle does the myosin head detach from actin?
Unbinding of myosin and actin
What occurs when troponin binds to calcium during muscle contraction?
Tropomyosin uncovers binding sites on actin
What is the significance of the sliding-filament model in explaining muscle contraction?
It describes the sliding of thick and thin filaments over one another during muscle contraction
What is involved in excitation-contraction coupling in muscle cells?
The sequence of events linking the action potential generated in a muscle cell to contraction
What is the primary function of neuromuscular junction in muscle contraction?
To link the action potential generated in a muscle cell by the motor neuron to contraction
Test your knowledge on the structure of skeletal muscles, including the connection to bones, muscle fibers, sarcolemma, and myofibrils.
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