Which part of an astronaut's body gets weaker in space?

Appeared in: ISRO 2024

Explanation

In the microgravity of space, muscles do not have to work against the force of gravity to support the body.
This lack of use leads to a condition called disuse atrophy, where muscle fibers shrink and overall muscle mass and strength decrease.
This effect is systemic, affecting not just the legs but also postural muscles of the back and the heart muscle.
Therefore, 'Muscles' is the most comprehensive and accurate answer, as the weakening is a whole-body phenomenon.

Option A: This is too specific. While leg muscles weaken significantly, muscle atrophy affects the entire body.
Option B: The brain does not physically weaken or lose mass in space. Functional changes related to balance and orientation may occur, but this is not structural weakness.
Option D: Hand muscles are continuously used for tasks and operating equipment in space, so they experience significantly less atrophy compared to large, weight-bearing muscles.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiological effects of microgravity on the human body as background academic context rather than a clinical decision trigger.
The deconditioning experienced by astronauts is a powerful model for understanding the effects of prolonged bed rest in patients.
Nursing interventions for bedridden patients, such as passive/active range-of-motion exercises, early ambulation, and monitoring for orthostatic hypotension, are based on the same principles used to keep astronauts healthy.
What if? If an astronaut did not perform their daily exercise regimen, their muscle loss could reach up to 20% over a 6-month mission, severely impairing their ability to function upon returning to Earth's gravity.

How to Approach the Question

First, identify the core concept of the question, which is the effect of the space environment (microgravity) on the human body.
Analyze the options provided: Legs, Brain, Muscles, Hands.
Evaluate each option based on physiological principles. Recognize that 'weakness' in this context refers to loss of mass and strength (atrophy).
Consider the scope of each option. 'Legs' are muscles, but 'Muscles' is a broader category.
Determine which option is the most comprehensive and accurate. While leg muscles do weaken, the effect is systemic. Therefore, 'Muscles' is the best answer.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 2A p. 123-125

E6 Physiology Essentials Sembulingam 10e Part 3 p. 16-18

Practise the full ISRO 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.