Description

Copyright infringement not intended

Picture Courtesy: THE HINDU

Context:

Indian Institute of Space Science and Technology (IIST) develops a 3D model revealing how microgravity raises astronauts' core body temperature.

Background

Unlike Earth, where gravity pulls fluids downward, space has almost no gravity, causing significant changes in the body. These changes affect bones, muscles, the heart, metabolism, and even temperature control.

The IIST study finds that microgravity increases the body’s core temperature, mainly due to fluid shifts, and this can impact astronauts’ health during long space missions, like those to Mars or beyond.

The model tracks how heat moves through the body in three dimensions. It considers factors like sweating, shivering, clothing, and heat produced by organs. By simulating these, the researchers predict how astronauts’ bodies respond to space conditions.

They also test their model against real data from astronauts on the International Space Station (ISS) and the former Soviet/Russian Mir space station, confirming its accuracy.

Thermoregulation

Thermoregulation is the body’s way of keeping its internal temperature stable, usually around 36.5–37°C.

On Earth, gravity helps distribute blood and fluids, aiding temperature control. In microgravity, fluids shift upward toward the head and chest, causing a “puffy face” and thinner legs, often called “stork legs.”

This redistribution affects how the body manages heat, leading to a warmer core (head, abdomen, chest) and cooler extremities (hands, feet).

The study reveals that in microgravity:

Core body temperature rises. After 2.5 months in space, with 30% less sweating and 36% higher metabolism, the core temperature can jump from 36.3°C to 37.8°C. During exercise, it may hit 40°C, which is dangerously high.
Exercise heats the body faster. Astronauts exercise daily to counter muscle and bone loss, but in space, their bodies warm up more quickly than on Earth, increasing risks like heat stress.
Fluid shifts play a big role. Blood and fluids move upward, reducing blood volume and altering heat distribution, which makes thermoregulation less efficient.

Why Is Microgravity So Challenging for the Body?

Blood redistribution. Without gravity, blood moves from the legs to the upper body, increasing fluid in the head and chest. This raises core temperature and reduces blood flow to the extremities, making hands and feet cooler.
Reduced blood volume. The body adapts to microgravity by decreasing blood volume, which affects circulation and heat distribution.
Muscle and bone loss. Muscles weaken and bones lose density (about 1% per month in weight-bearing bones) because they don’t work against gravity. This reduces the body’s ability to generate and manage heat.
Metabolic changes. Metabolism increases in space, producing more heat, while sweating decreases, limiting cooling.
Cardiovascular strain. The heart changes shape and pumps less blood, reducing circulation efficiency, which impacts thermoregulation.
Immune system effects. Microgravity weakens the immune system, increasing infection risks, which can complicate temperature regulation if the body fights illness.

Source:

THE HINDU

PRACTICE QUESTION

Q.In the question given below, there are two statements marked as Assertion (A) and Reason (R). Mark your answer as per the codes provided:

Assertion (A): In microgravity, astronauts experience muscle atrophy and bone density loss.

Reason (R): Skeletal muscles and bones adapt by reducing mass when mechanical loading decreases.

Which of the options given below is correct?

A) Both A and R are true, and R is the correct explanation for A.

B) Both A and R are true, but R is not the correct explanation for A.

C) A is true, but R is false.

D) A is false, but R is true.

Answer: A

Explanation:

Assertion (A) is True: In the absence of Earth's gravity, astronauts don't use their muscles and bones in the same way they do on Earth, leading to weakening and loss of mass.

Reason (R) is True: Muscles and bones are living tissues that adapt to the demands placed upon them. When those demands, particularly the force of gravity, are reduced, the body conserves energy and resources by reducing the mass of these tissues.

The lack of mechanical loading due to microgravity (as stated in Reason R) is the direct cause of the muscle atrophy and bone density loss observed in astronauts (as stated in Assertion A).