Sliding Filament Theory and the Sacromere quiz #1 Flashcards
Sliding Filament Theory and the Sacromere quiz #1
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Which of the following marks the boundaries of a sarcomere? A) M-line B) Z-discs C) A-band D) I-band
B) Z-discs What causes the myosin head to disconnect from actin?
The binding of ATP to the myosin head causes it to release from actin. What happens when calcium ions bind to troponin?
When calcium ions bind to troponin, it causes a conformational change that moves tropomyosin away from the myosin binding sites on actin, allowing muscle contraction to occur. What happens to the actin and myosin during a muscle contraction?
During muscle contraction, actin and myosin filaments slide past each other, increasing their overlap and shortening the sarcomere. What forms a cross-bridge?
A cross-bridge is formed when a myosin head binds to an actin filament. Within a sarcomere, what is the role of the M-line?
The M-line anchors the myosin filaments in the center of the sarcomere. Which statements correctly describe changes in a skeletal muscle cell during muscle contraction?
During muscle contraction, the sarcomere shortens, the H-zone decreases, and the overlap between actin and myosin increases. When calcium ions bind to troponin, what is the result?
The binding of calcium ions to troponin results in the movement of tropomyosin, exposing the myosin binding sites on actin. Regarding skeletal muscle contraction, what is the role of ATP?
ATP is required for the detachment of myosin heads from actin and for the re-cocking of the myosin heads for another cycle of contraction. What happens when troponin and tropomyosin block the active sites of actin?
When troponin and tropomyosin block the active sites of actin, myosin cannot bind to actin, preventing muscle contraction. What is the letter associated with the dark bands in a sarcomere?
The letter associated with the dark bands in a sarcomere is A, referring to the A-band. What is explained by the sliding filament theory?
The sliding filament theory explains how muscle contraction occurs through the sliding of actin and myosin filaments past each other, shortening the sarcomere. What is released when myosin heads attach to actin filaments?
When myosin heads attach to actin filaments, ADP and inorganic phosphate are released. What generates the force that shortens the sarcomeres to bring about muscle contraction?
The force that shortens the sarcomeres is generated by the power stroke of the myosin heads pulling on the actin filaments. What does the sliding filament theory describe?
The sliding filament theory describes the process by which actin and myosin filaments slide past each other to produce muscle contraction. What is the role of calcium in the cross bridge cycle?
Calcium binds to troponin, causing a conformational change that moves tropomyosin away from the myosin binding sites on actin, allowing cross-bridge formation. What is a power stroke during muscle contraction?
A power stroke is the action of the myosin head pulling the actin filament towards the center of the sarcomere, resulting in muscle contraction. What is the part of a sarcomere that contains only thin filaments?
The part of a sarcomere that contains only thin filaments is the I-band. Which specific region of the sarcomere contains only thin filaments?
The I-band is the specific region of the sarcomere that contains only thin filaments. Which of the following statements about H zones and I bands is true? A) H zones contain only actin B) I bands contain only myosin C) H zones contain only myosin D) I bands contain both actin and myosin
C) H zones contain only myosin What happens when a myosin head releases from actin?
When a myosin head releases from actin, it is re-cocked by the hydrolysis of ATP, preparing it for another cycle of contraction. What causes the release of calcium ions into the sarcoplasm from the terminal cisterns?
The release of calcium ions into the sarcoplasm is triggered by an action potential traveling along the sarcolemma and down the T-tubules. What are the two components of a sarcomere?
The two main components of a sarcomere are the thick filaments (myosin) and the thin filaments (actin). Thin filaments are composed of how many strands of fibrous actin?
Thin filaments are composed of two strands of fibrous actin twisted together. What is the area in the center of the A band where there are no actin myofilaments?
The area in the center of the A band where there are no actin myofilaments is called the H-zone. What's the consequence if the myosin heads cannot bind to the actin?
If the myosin heads cannot bind to actin, muscle contraction cannot occur. What is the main component of thin filaments?
The main component of thin filaments is actin. Which statement describes a sarcomere?
A sarcomere is the smallest functional unit of muscle contraction, defined by the area between two Z-discs. What substance causes the actin to change shape?
Calcium ions cause the actin to change shape by binding to troponin, which moves tropomyosin away from the myosin binding sites. What happens to the thick and thin filaments during muscle contraction?
During muscle contraction, the thick and thin filaments slide past each other, increasing their overlap and shortening the sarcomere. What part of the myosin filaments bind to actin?
The myosin heads bind to actin. Which filament is thicker, actin or myosin?
Myosin is the thicker filament. Remind me again...what is the sliding filament model of muscle contraction?
The sliding filament model of muscle contraction describes how myosin heads pull actin filaments towards the center of the sarcomere, causing it to shorten. What does the sliding filament model describe during muscle contraction?
The sliding filament model describes the process by which actin and myosin filaments slide past each other to produce muscle contraction. During contraction of a sarcomere, what happens to the H-zone?
During contraction of a sarcomere, the H-zone becomes smaller as the overlap between actin and myosin increases. How does myosin and actin interact with each other?
Myosin heads bind to actin filaments, forming cross-bridges, and pull the actin towards the center of the sarcomere during contraction. Which of the following contains overlapping thick and thin filaments? A) I-band B) A-band C) H-zone D) Z-disc
B) A-band What releases calcium into the sarcoplasm?
The sarcoplasmic reticulum releases calcium into the sarcoplasm. The binding of calcium to which molecule causes the myosin binding sites to be exposed?
The binding of calcium to troponin causes the myosin binding sites on actin to be exposed. Which of the following best describes the term sarcomere? A) The area between two M-lines B) The area between two Z-discs C) The area between two A-bands D) The area between two I-bands
B) The area between two Z-discs
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