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The individual unit of muscle contraction in a muscle fibril is referred to as the __________.
The individual contractile unit of a muscle fibril is referred to as the sarcomere. These units are made of actin and myosin filaments and joined by Z-lines. The sliding filament theory refers to the idea that muscle contraction is the result of myosin strands within the fibril pulling themselves along actin strands similar to pulling on a rope, which shortens the whole sarcomere. The sarcolemma is the specialized cell membrane around the muscle fibril, and the sarcoplasmic reticulum is the smooth endoplasmic reticulum found within the muscle cell.
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Which of the following is the name of the modified endoplasmic reticulum found in muscle cells?
Muscle cells have a specialized endoplasmic reticulum called the sarcoplasmic reticulum. The sarcoplasmic reticulum regulates the calcium ion concentration in the cytoplasm of striated muscle cells, and so plays a significant role in muscle contraction and relaxation. The T-tubule is a specialized invagination of the sarcoplasmic reticulum, and the sarcomere is the single contractile unit of a muscle fibril. There is no muscle structure called the mycoplasmic reticulum.
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Which of the following is the correct order of structures in a skeletal muscle, from largest to smallest?
The largest unit of muscle tissue is the fascicle. Each fascicle is made up of a bundle of muscle fibers, and every muscle fiber is made up of many fibrils (called myofibrils).
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The muscle body is encased in which of the following?
The muscle body is encased in a fibrous elastic sheath called the epimysium (epi meaning on or above and mys meaning muscle). It is composed of dense irregular connective tissue and is continuous with tendon fibers. The perimysium surrounds muscle fascicles, while the endomysium surrounds muscle fibers.
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Which of the following correctly describes an isometric muscle contraction?
Isometric muscle contraction are those in which the tension in the muscle increases, but the muscle does not change length, nor does the angle of the joint change. An example would be attempting to push or lift an object that is too heavy to move. This is in contrast to isotonic contraction, in which muscle tension remains constant, but the muscle length and joint angle both change.
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Which of the following is the smallest unit of contractile tissue in cardiac and skeletal muscle cells?
The smallest contractile unit in muscle tissue is the sarcomere. Myofibrils are made up of many sarcomeres attached end-to-end at a series of dark lines (hence the term "striated") called Z lines. Each sarcomere contains actin and myosin filaments, which pull together during contraction to shorten the sarcomere.
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The sliding filament theory of muscle contraction involves the __________ attaching to __________ and then pulling during the power stroke.
The sliding filament theory of muscle contraction involves the myosin head attaching to actin and then pulling during the power stroke. Troponin is a protein attached to tropomyosin, a thin strand wrapping around the actin filament. When calcium enters the cell, troponin moves toward it, pulling the tropomyosin strand away from actin binding sites and allowing the myosin head to bind.
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During contraction, the A band of the sarcomere does which of the following?
The A band in the sarcomere is created by the bipolar myosin filaments, joined at the M band. During contraction, the heads of the myosin filaments bind with the actin filament and pull it toward the M band at the center of the sarcomere. The myosin filaments do not themselves change length, and because of that the width of the A band does not change during contraction.
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In the sliding filament theory of muscle contraction, all but which of the following are functions of ATP?
According to the sliding filament theory of muscle contraction, ATP binds to the myosin head and is hydrolyzed to ADP and inorganic phosphate. The energy released during this change draws the myosin head back into a high energy state, from which it is able to bind with actin and execute its "power stroke," leading to muscle contraction. ADP and inorganic phosphate then are released from the myosin head and replaced by a new molecule of ATP, which allows the myosin head to detach from the actin binding site.
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Which of the following molecules binds to troponin during muscle contraction, triggering tropomyosin to move away from the actin binding sites and allowing the myosin head to form a cross bridge?
During a muscle cell action potential, calcium enters the cell via t-tubules, which are specialized invaginations of the sarcoplasmic reticulum. Calcium binds with troponin, which pulls the tropomyosin strand away from actin binding sites and allows myosin heads to bind. Neither sodium nor potassium bind to troponin, and ATP and ADP both bind to myosin, rather than troponin.
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All of the following features are unique to cardiac muscle cells except:
Cardiac muscle cells are striated, branching cells that are linked by structures called intercalated discs. These discs are composed of gap junctions, which allow the free passage of electrical signaling between heart cells, and very strong attachment points called desmosomes.
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A nurse is examining a patient who has muscle pain and fatigue after working out. He determines that the patient has muscle strain. This is generally caused by which of the following?
Muscle strain is often caused by over stretching, during which actin and myosin heads are pulled to the extent that they are no longer overlapping, possibly to the point of causing tears in muscle tissue. Tears in ligaments are sprains, rather than strains.
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Which is the only muscle type that is non-striated?
The only type of muscle that is not striated is smooth muscle. Smooth muscle does not use sarcomeres for contraction - rather, each muscle cell is a spindle that is covered in a mesh of contractile fibrils. These fibrils contract in unison when calcium enters the cell.
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The individual unit of muscle contraction in a muscle fibril is referred to as the __________.
The individual contractile unit of a muscle fibril is referred to as the sarcomere. These units are made of actin and myosin filaments and joined by Z-lines. The sliding filament theory refers to the idea that muscle contraction is the result of myosin strands within the fibril pulling themselves along actin strands similar to pulling on a rope, which shortens the whole sarcomere. The sarcolemma is the specialized cell membrane around the muscle fibril, and the sarcoplasmic reticulum is the smooth endoplasmic reticulum found within the muscle cell.
Compare your answer with the correct one above
Which of the following is the name of the modified endoplasmic reticulum found in muscle cells?
Muscle cells have a specialized endoplasmic reticulum called the sarcoplasmic reticulum. The sarcoplasmic reticulum regulates the calcium ion concentration in the cytoplasm of striated muscle cells, and so plays a significant role in muscle contraction and relaxation. The T-tubule is a specialized invagination of the sarcoplasmic reticulum, and the sarcomere is the single contractile unit of a muscle fibril. There is no muscle structure called the mycoplasmic reticulum.
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Which of the following is the correct order of structures in a skeletal muscle, from largest to smallest?
The largest unit of muscle tissue is the fascicle. Each fascicle is made up of a bundle of muscle fibers, and every muscle fiber is made up of many fibrils (called myofibrils).
Compare your answer with the correct one above
The muscle body is encased in which of the following?
The muscle body is encased in a fibrous elastic sheath called the epimysium (epi meaning on or above and mys meaning muscle). It is composed of dense irregular connective tissue and is continuous with tendon fibers. The perimysium surrounds muscle fascicles, while the endomysium surrounds muscle fibers.
Compare your answer with the correct one above
Which of the following correctly describes an isometric muscle contraction?
Isometric muscle contraction are those in which the tension in the muscle increases, but the muscle does not change length, nor does the angle of the joint change. An example would be attempting to push or lift an object that is too heavy to move. This is in contrast to isotonic contraction, in which muscle tension remains constant, but the muscle length and joint angle both change.
Compare your answer with the correct one above
Which of the following is the smallest unit of contractile tissue in cardiac and skeletal muscle cells?
The smallest contractile unit in muscle tissue is the sarcomere. Myofibrils are made up of many sarcomeres attached end-to-end at a series of dark lines (hence the term "striated") called Z lines. Each sarcomere contains actin and myosin filaments, which pull together during contraction to shorten the sarcomere.
Compare your answer with the correct one above
The sliding filament theory of muscle contraction involves the __________ attaching to __________ and then pulling during the power stroke.
The sliding filament theory of muscle contraction involves the myosin head attaching to actin and then pulling during the power stroke. Troponin is a protein attached to tropomyosin, a thin strand wrapping around the actin filament. When calcium enters the cell, troponin moves toward it, pulling the tropomyosin strand away from actin binding sites and allowing the myosin head to bind.
Compare your answer with the correct one above