ATI RN
Questions for Muscular System Questions
Question 1 of 5
Which of the following steps in muscle contraction would occur first?
Correct Answer: A
Rationale: Muscle contraction begins when a nerve impulse triggers the sarcolemma, the muscle fiber's membrane, to depolarize, generating an action potential. This electrical event, initiated by acetylcholine at the neuromuscular junction, spreads across the fiber's surface, reaching T-tubules invaginations that relay the signal inward. Only then does calcium release from the sarcoplasmic reticulum occur, binding to troponin, which shifts tropomyosin to expose actin's myosin-binding sites. Filament sliding follows as myosin heads engage actin, powered by ATP. The sarcolemma's depolarization, measurable via electromyography, precedes all intracellular steps, occurring within milliseconds. Calcium release and T-tubule transmission follow sequentially, not simultaneously, as the signal propagates. Binding site exposure and sliding depend on calcium's presence, placing them later. Physiology texts sequence this: action potential (1-2 ms), T-tubule spread, calcium surge (10-20 ms), then contraction. This initial electrical trigger is foundational, distinguishing it from subsequent chemical and mechanical events in the excitation-contraction coupling cascade.
Question 2 of 5
When preparing a patient for electromyography (EMG), the nurse will instruct the patient to:
Correct Answer: B
Rationale: EMG assesses muscle and nerve function by recording electrical activity, requiring clear signals. Caffeine, a stimulant, can increase muscle tension or jitteriness, potentially skewing results, so avoiding it for 3 hours prior is standard. Smoking cessation for 12 hours isn't typically required, as its effect on EMG is less direct. Muscle relaxants would dampen activity, defeating the test's purpose of measuring natural responses. While EMG can take time, 2 hours isn't standard for all cases, and preparation focuses more on accuracy than duration. Refraining from caffeine ensures the test reflects true neuromuscular status, making it the key instruction for reliable outcomes.
Question 3 of 5
The nurse explains that the major advantage of the external fixation device is that the patient:
Correct Answer: C
Rationale: External fixation stabilizes fractures with pins and a frame outside the skin, allowing precise alignment. Its major advantage is greater freedom of movement, as the limb isn't encased like in a cast, permitting easier access for wound care and some mobility, depending on the injury. Healing speed depends on the fracture, not the device alone. Weight-bearing varies by case and isn't immediate. Pain levels aren't inherently lower than other methods. Movement freedom stands out, enhancing patient comfort and care flexibility, distinguishing external fixation from more restrictive options like casts or traction.
Question 4 of 5
While the nurse is giving morning care to a patient who sustained a fractured pelvis and bilateral fractures of the femur in a motorcycle accident yesterday, the patient complains of shortness of breath and is audibly wheezing. An assessment of the oxygen saturation reveals 76%. The initial intervention by the nurse should be to:
Correct Answer: C
Rationale: Sudden shortness of breath, wheezing, and 76% oxygen saturation post-fracture suggest a fat embolism, a life-threatening complication from long bone trauma. Administering oxygen at 4-5 L/min via nasal cannula is the initial step to boost oxygenation, stabilizing the patient while further help is sought. Alerting the code team is premature without first aiding breathing. Informing the charge nurse follows oxygen delivery, as does raising to high Fowler's to ease breathing but oxygen comes first. This rapid response addresses hypoxia directly, critical in trauma where respiratory decline can escalate fast, buying time for diagnosis and treatment.
Question 5 of 5
The pelvic floor; the space between the anus and the scrotum in the male and between the anus and the vulva in the female.
Correct Answer: C
Rationale: The perineum is the region of the pelvic floor between the anus and scrotum in males or vulva in females, encompassing both the anal and urogenital triangles. It serves as the external base of the pelvic cavity and contains muscles, nerves, and other structures. Compartment refers to muscle groups, not this region. The urogenital triangle is only part of the perineum, not the whole area. Fixators are stabilizing muscles, unrelated to this anatomical space. The perineum's definition matches the question perfectly, making it the correct answer, as it broadly describes the pelvic floor area between these landmarks, critical for understanding pelvic anatomy and clinical conditions like perineal tears.