Nursing practice questions with comprehensive rationales
NurseDive Free Nursing Practice Question
What is the functional role of the T tubules?
A. Hold cross bridges in place in a resting muscle
Cross bridges are formed between actin and myosin during contraction. T tubules do not hold them in place; their role is electrical, not structural.
B. Support the muscle fiber
While T tubules are embedded in the muscle fiber, their function is not to provide structural support. That role is fulfilled by connective tissues like endomysium and cytoskeletal proteins.
C. Stabilize the G and F actin
G and F actin are stabilized by proteins like tropomyosin and nebulin, not T tubules. T tubules are involved in electrical signaling.
D. Enhance spread of muscle action potential throughout muscle fiber
This is the correct answer. T tubules are invaginations of the sarcolemma that conduct action potentials deep into the muscle fiber. This ensures that the signal for contraction reaches all parts of the muscle simultaneously, triggering calcium release from the sarcoplasmic reticulum.
E. Synthesize glucose to provide energy for muscle contraction
Glucose synthesis occurs in the liver and other tissues via gluconeogenesis. Muscle cells use glucose for energy but do not synthesize it through T tubules.
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Full Explanation
Choice A reason: Cross bridges are formed between actin and myosin during contraction. T tubules do not hold them in place; their role is electrical, not structural.
Choice B reason: While T tubules are embedded in the muscle fiber, their function is not to provide structural support. That role is fulfilled by connective tissues like endomysium and cytoskeletal proteins.
Choice C reason: G and F actin are stabilized by proteins like tropomyosin and nebulin, not T tubules. T tubules are involved in electrical signaling.
Choice D reason: This is the correct answer. T tubules are invaginations of the sarcolemma that conduct action potentials deep into the muscle fiber. This ensures that the signal for contraction reaches all parts of the muscle simultaneously, triggering calcium release from the sarcoplasmic reticulum.
Choice E reason: Glucose synthesis occurs in the liver and other tissues via gluconeogenesis. Muscle cells use glucose for energy but do not synthesize it through T tubules.
Similar Questions
What motion is being used when you stand on your tiptoes to grab something off of the top shelf?
A. Inversion
Inversion refers to turning the sole of the foot inward, toward the midline. It is a side-to-side movement at the ankle and does not elevate the heel or involve tiptoe posture.
B. Plantar flexion
Plantar flexion is the correct answer. It involves pointing the toes downward and lifting the heel off the ground, which is exactly the motion used when standing on tiptoes. This movement occurs at the ankle joint and is essential for actions like walking, jumping, and reaching upward.
C. Eversion
Eversion is the opposite of inversion and involves turning the sole of the foot outward. Like inversion, it is a lateral movement and unrelated to tiptoe posture.
D. Dorsiflexion
Dorsiflexion is the opposite of plantar flexion. It involves lifting the toes upward toward the shin, such as when walking on heels. It does not help in reaching upward.
E. Supination
Supination refers to rotating the forearm so the palm faces upward or forward. It is unrelated to foot movement or standing on tiptoes.
Full Explanation
Choice A reason: Inversion refers to turning the sole of the foot inward, toward the midline. It is a side-to-side movement at the ankle and does not elevate the heel or involve tiptoe posture.
Choice B reason: Plantar flexion is the correct answer. It involves pointing the toes downward and lifting the heel off the ground, which is exactly the motion used when standing on tiptoes. This movement occurs at the ankle joint and is essential for actions like walking, jumping, and reaching upward.
Choice C reason: Eversion is the opposite of inversion and involves turning the sole of the foot outward. Like inversion, it is a lateral movement and unrelated to tiptoe posture.
Choice D reason: Dorsiflexion is the opposite of plantar flexion. It involves lifting the toes upward toward the shin, such as when walking on heels. It does not help in reaching upward.
Choice E reason: Supination refers to rotating the forearm so the palm faces upward or forward. It is unrelated to foot movement or standing on tiptoes.
The protein that acts as a calcium receptor in skeletal muscle is:
A. Actin
Actin is a structural protein that forms the thin filaments in muscle fibers. While it interacts with myosin during contraction, it does not bind calcium directly.
B. Tropomyosin
Tropomyosin is a regulatory protein that blocks the myosin-binding sites on actin in a resting muscle. It shifts position when calcium binds to troponin but does not itself bind calcium.
C. Titin
Titin is a large elastic protein that helps maintain the structural integrity of the sarcomere and contributes to passive elasticity. It does not function as a calcium receptor.
D. Troponin
Troponin is the correct answer. It is a regulatory protein complex associated with the thin filament. When calcium ions bind to troponin, it induces a conformational change that moves tropomyosin away from actin’s binding sites, allowing muscle contraction to occur.
E. Dystrophin
Dystrophin is a structural protein that connects the cytoskeleton of muscle fibers to the extracellular matrix. It is important for muscle integrity but does not bind calcium.
Full Explanation
Choice A reason: Actin is a structural protein that forms the thin filaments in muscle fibers. While it interacts with myosin during contraction, it does not bind calcium directly.
Choice B reason: Tropomyosin is a regulatory protein that blocks the myosin-binding sites on actin in a resting muscle. It shifts position when calcium binds to troponin but does not itself bind calcium.
Choice C reason: Titin is a large elastic protein that helps maintain the structural integrity of the sarcomere and contributes to passive elasticity. It does not function as a calcium receptor.
Choice D reason: Troponin is the correct answer. It is a regulatory protein complex associated with the thin filament. When calcium ions bind to troponin, it induces a conformational change that moves tropomyosin away from actin’s binding sites, allowing muscle contraction to occur.
Choice E reason: Dystrophin is a structural protein that connects the cytoskeleton of muscle fibers to the extracellular matrix. It is important for muscle integrity but does not bind calcium.
Opposition is the movement of any bone in the body that opposes another bone in the body.
A. True
Opposition is a specific movement that occurs primarily in the thumb. It refers to the ability of the thumb to touch the tips of the other fingers, allowing grasping and manipulation. This movement involves the thumb opposing the fingers, hence the term.
B. False
False is incorrect because opposition is a well-defined movement in anatomy, particularly in the hand.
C. Only in the lower limbs
D. Only in the spine
Full Explanation
Choice A reason: Opposition is a specific movement that occurs primarily in the thumb. It refers to the ability of the thumb to touch the tips of the other fingers, allowing grasping and manipulation. This movement involves the thumb opposing the fingers, hence the term.
Choice B reason: False is incorrect because opposition is a well-defined movement in anatomy, particularly in the hand.