ATI RN
Questions for Muscular System Questions
Question 1 of 5
Stimulation of the heat-loss center causes
Correct Answer: C
Rationale: The heat-loss center (hypothalamus) activates sweat glands to increase output, cooling via evaporation when overheated. Blood vessels dilate (not constrict, a) to release heat. Breathing may adjust but isn't slow/shallow primarily. Not all only 'c' fits. Sweating's cooling role, per thermoregulation, makes 'c' correct.
Question 2 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 3 of 5
The nurse uses a visual aid to show the pathologic muscle tone changes that result in footdrop. Those changes are:
Correct Answer: B
Rationale: Footdrop occurs when the ankle dorsiflexors, responsible for lifting the foot, weaken or become overstretched, often due to immobility or nerve damage. This allows the plantar flexors (calf muscles) to dominate, pulling the foot downward. The flexor muscles, including dorsiflexors like the tibialis anterior, stretch and lose tone, leading to the characteristic drooping posture. Calf muscles stretching would imply the opposite, raising the foot, which doesn't fit footdrop. Toes curling downward suggests a different condition, like claw toes, not the flaccid drop of this issue. Thigh muscle contraction is unrelated, as footdrop stems from lower leg dynamics. The visual aid highlights this imbalance, showing how flexor overstretching results in the inability to lift the foot, a key feature of the condition.
Question 4 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 5 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.