The first event to occur in muscle relaxation is that:
tropomyosin returns to its original position.
myosin cross-bridges are prevented from binding to actin.
the sarcoplasmic reticulum begins actively pumping calcium back into its sacs.
acetylcholine is released.
The Correct Answer is C
A. tropomyosin returns to its original position: This happens later in the process; it is a result of calcium removal, not the first event.
B. myosin cross-bridges are prevented from binding to actin: This is the final stage of relaxation where the physical contraction stops.
C. the sarcoplasmic reticulum begins actively pumping calcium back into its sacs: Relaxation officially begins when nerve stimulation stops and the sarcoplasmic reticulum uses active transport to remove Ca 2+ from the sarcoplasm.
D. acetylcholine is released: This is the first step of muscle contraction, not relaxation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Sternocleidomastoid and abdominal muscles: The sternocleidomastoid is an accessory muscle for forced inspiration, not expiration.
B. Sternocleidomastoid and intercostals: Again, the sternocleidomastoid helps lift the ribcage for inhalation.
C. External intercostals and pectoralis muscles: Both of these are used to expand the chest cavity during inspiration.
D. Abdominal muscles and internal intercostals: Forced expiration is an active process where abdominal muscles push the diaphragm up and internal intercostals pull the ribs down to force air out.
Correct Answer is A
Explanation
A. osteoblasts: These are the bone-forming cells that actively produce and secrete the organic bone matrix.
B. osteocytes: These are mature bone cells that maintain the matrix but are no longer responsible for producing it.
C. osteoclasts: These cells break down or "resorb" bone tissue.
D. chondrocytes: These cells produce the matrix for cartilage, not bone.
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