Gravity and the human body - Jay Buckey

Summary

This transcript explores the physiological challenges humans face during long-term space travel, focusing on the effects of microgravity on bone and muscle mass, cardiovascular health, and the balance system. It highlights how the body adapts to weightlessness, leading to muscle atrophy, bone loss, and altered cardiovascular function. The speaker raises thought-provoking questions about the long-term effects of growing up in space, drawing parallels to a study on sensory deprivation in kittens to suggest that without gravity, key systems might develop differently. These changes could have lasting impacts on human physiology, posing intriguing possibilities for future space exploration and colonization.

Takeaways

• 😀 People in space for long periods experience muscle and bone loss due to the absence of gravity, similar to how muscles shrink when a cast is removed.
• 😀 The body adapts to physical stress, meaning bones and muscles are constantly changing, not static.
• 😀 In weightlessness, bone density decreases, and muscles that counteract gravity (postural muscles) lose strength.
• 😀 The cardiovascular system, including the heart and blood vessels, also adapts to weightlessness, potentially affecting blood circulation.
• 😀 On Earth, gravity helps pump blood to the head when standing; this process can be disrupted in space, which may affect circulation.
• 😀 The balance system, essential for preventing falls, is highly influenced by gravity, and changes in space affect this system.
• 😀 While in space, the brain adjusts to weightlessness, which isn't immediately noticeable but affects balance upon returning to Earth.
• 😀 All life on Earth has evolved in the presence of gravity, shaping how humans develop skills like walking and balancing.
• 😀 If a human grew up without gravity, the development of muscles, balance, and cardiovascular systems might differ from Earth-born individuals.
• 😀 A study with a kitten, where a patch was placed over one eye, showed that sensory input during development shapes brain connections. This suggests that without gravity, humans' physiological systems could develop differently.

Q & A

What happens to muscles and bones in space due to the lack of gravity?

In space, without gravity, bones lose density and muscles that are responsible for supporting the body against gravity shrink and weaken. This happens because the body no longer needs to support its own weight, leading to a reduction in muscle and bone mass over time.

How does the body adapt to the absence of gravity in space?

The body adapts to weightlessness by reducing the demand on systems that are dependent on gravity. For example, muscles and bones become weaker, cardiovascular systems change to accommodate the lack of gravity, and the balance system also re-adjusts to function in a weightless environment.

Why do astronauts experience changes in their cardiovascular system while in space?

In space, astronauts do not need to work against gravity to pump blood to their heads, as they would on Earth. As a result, their cardiovascular system undergoes changes, potentially affecting blood circulation and heart function during long-term weightlessness.

What is the significance of the Hubel and Wiesel experiment with kittens?

The Hubel and Wiesel experiment demonstrated that sensory input is crucial for brain development. By covering one eye of a kitten, they found that the brain adapted and did not form the necessary connections to that eye. This suggests that sensory experiences play a key role in shaping brain functions.

How does the balance system change in space, and when do astronauts notice it?

In space, the balance system adapts to the weightless environment, which alters how the body perceives and reacts to balance. Astronauts don’t notice this change while in space, but they often experience difficulty maintaining their balance when they return to Earth because their balance system has been adapted to weightlessness.

What are the potential long-term effects of living in space on a human’s ability to function on Earth?

Long-term exposure to space and weightlessness may lead to permanent changes in muscle strength, bone density, cardiovascular function, and balance. If a person were raised in space without gravity, these systems might develop in ways that could make it difficult for them to function normally on Earth.

What role does gravity play in the development of human physiology?

Gravity plays a crucial role in the development of various human physiological systems. It influences muscle and bone strength, cardiovascular health, and the balance system. These systems have evolved specifically to function in a gravitational environment, and the absence of gravity could lead to significant developmental differences.

How does the absence of gravity affect bone density in astronauts?

In weightlessness, astronauts experience a reduction in bone density because the bones no longer need to support the body’s weight. Over time, this can lead to weakened bones, increasing the risk of fractures and other bone-related issues.

Why might a person who grew up in space have difficulty adjusting to life on Earth?

A person who grew up in space would have developed different physiological systems, particularly in relation to muscle, bone, and balance functions. These adaptations to weightlessness could make it challenging for them to function in Earth's gravity, as their body systems would not be accustomed to the forces of gravity.

What questions remain unanswered regarding the effects of space on human development?

Key unanswered questions include how exactly growing up in space would affect human development in the long term, particularly with regard to the balance system, cardiovascular health, and muscle function. More research is needed to understand whether these changes are reversible and how they might affect a person’s ability to adapt to Earth’s environment.