Prolonged stay in space will lead to all of the following changes in the body except?

SJH Nursing Officer - 2019

Applied Physiology

Easy

Appeared in: SJH Nursing Officer - 2019

Explanation

'Increase cardiac output' because this statement is false.
In a microgravity environment, the heart does not have to pump blood against gravity, leading to cardiac deconditioning.
This deconditioning involves atrophy (weakening and shrinking) of the heart muscle.
As a result, the heart's maximum pumping capacity, or cardiac output, decreases over time.
All other options represent true physiological changes that occur during prolonged spaceflight.

Option A: This is a true effect of prolonged spaceflight. In microgravity, fluid shifts from the lower body to the upper body, which the body interprets as fluid overload, triggering increased urination (diuresis) and a subsequent decrease in total blood volume.
Option B: This is a true effect. Prolonged spaceflight leads to a reduction in red blood cell mass, a condition known as 'space anemia'. This directly causes a decrease in hematocrit (the proportion of blood volume occupied by red blood cells).
Option D: This is a well-documented effect of microgravity. Without the need to support the body against gravity, muscles, particularly the anti-gravity muscles of the legs and spine, undergo significant atrophy (wasting), leading to a substantial decrease in muscle mass and strength.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiological adaptations to microgravity during spaceflight as background academic context rather than a clinical decision trigger.
Understanding these changes is critical for astronaut health and safety during and after long-duration missions.
Countermeasures are essential. Astronauts on the International Space Station (ISS) perform about two hours of rigorous exercise daily using treadmills, stationary bikes, and resistance devices to mitigate muscle and bone loss and maintain cardiovascular health.
What if? - If an astronaut did not follow a strict exercise regimen in space, their return to Earth's gravity would be far more dangerous. They would face a high risk of fainting (orthostatic intolerance) due to poor cardiovascular adaptation, bone fractures from minor falls, and extreme muscle weakness, making even simple movements difficult.

How to Approach the Question

First, identify the keyword 'except' in the question. This signals that you are looking for the one option that is a false statement.
Recall or deduce the major physiological effects of microgravity on the human body. Think about what happens when the body no longer has to work against gravity.
Evaluate each option:
Does blood volume change? Yes, fluid shifts cause it to decrease.
Does hematocrit change? Yes, 'space anemia' causes it to decrease.
Does muscle strength change? Yes, disuse atrophy causes it to decrease.

Concept Tested & Keywords

Concept Tested: Physiological adaptations to microgravity during spaceflight.
Stem keywords: Prolonged stay in space, changes in the body
Lead-in keywords: except
Negative lead-in flag: The question asks for the EXCEPTION, meaning you must find the one option that is NOT a true effect of prolonged space travel.

Q5TccCDtsQWWRdi6ALo2qU

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

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