What is the energy source for muscle contraction?
Deoxyribose
Acetylcholine
nucleic acids
Adenosine triphosphate
The Correct Answer is D
Rationale:
A. This is a sugar component of DNA, not an energy source for muscle contraction.
B. This is a neurotransmitter that stimulates muscle fibers at the neuromuscular junction, initiating contraction. However, it is a signaling molecule, not the direct energy source.
C. These (DNA and RNA) store and transmit genetic information but do not supply energy for muscle contraction.
D. ATP is the immediate and primary energy source for muscle contraction. It provides energy for the cross-bridge cycle between actin and myosin filaments, as well as for pumping calcium back into the sarcoplasmic reticulum during relaxation. Without ATP, muscle contraction and relaxation cannot occur (as seen in rigor mortis).
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Rationale:
A. This is the visible part of the hair above the skin’s surface. It is made of keratinized cells and does not have the ability to contract or move.
B. This is the portion of the hair located below the surface of the skin within the follicle. Like the shaft, it does not control hair movement.
C. The follicle is the structure in the dermis that surrounds and nourishes the hair root, providing the base for hair growth. While important for hair formation, it does not cause the hair to stand erect.
D. The arrector pili are small bands of smooth muscle fibers attached to hair follicles. When these muscles contract (in response to cold, fear, or emotional stimuli), they pull the hair follicle upright, causing the hair to "stand on end" (a phenomenon known as piloerection or "goosebumps").
Correct Answer is B
Explanation
Rationale:
A. Secretes the lubricating fluid for a synovial joint describes the synovial membrane, not a bursa.
B. Prevents friction between skin and bone, or a muscle tendon and bone; A bursa is a small, fluid-filled sac that cushions and reduces friction between moving structures, such as tendons, muscles, and bones. This helps facilitate smooth movement and prevents tissue damage.
C. Surrounds a tendon at the point where the tendon crosses a joint describes a tendon sheath, which is distinct from a bursa.
D. Is the strong band of connective tissue that holds bones together at a synovial joint refers to a ligament, not a bursa.
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