E155 What have we learned about humans in space?

What aspect of space travel will likely be the most problematic during long-term space travel (e.g. going to Mars) and why?

Ionizing radiation because it damages DNA, proteins and lipids.

Were there any benefits to running on a treadmill for long periods (>200min/week) while in space?

• Yes, those who ran on the treadmill for long periods of time experienced less atrophy in space 

• Maintains gastrocnemius muscle enzymes 

• Increased fatigue with weightlessness cannot be directly caused by a decline in muscle enzyme capacity

Which fiber types atrophy the most in space? Type I (slow oxidative) or type II (fast glycolytic)?

Type i fibers atrophy the most

What are the effects of microgravity on the heart and blood vessels?

• Blood and fluids are pushed upward from legs to core - decrease in blood and fluid in the heat and blood vessels 

• Swelling in the face and head -> increase brain pressure, hearing loss, brain edema, and eye deformations 

• Heart becomes the shape of a round ball

What organ systems are affected by microgravity?

• Cardiovascular - heart weakens and shrinks 

• Muscular 

• Skeletal - bone weakening/ osteoporosis

What were some of the greatest psychological challenges?

Fear and not knowing how your body will react

doing microgravity research on earth

• bed rest, head down

• psych = comparable to Antartica in winter; simulations

• rodents for muscle studies = hindlimb suspension with no ground force (atrophy)

why does microgravity lead to a loss of muscle mass?

No weight bearing activity, reduces mechanical stress on muscles, muscles atrophy in space

• less work = disuse = atrophy

• mechanical stress → Ca2+ → different pathways → difference in muscle fibers

how do muscle fiber types change in microgravity? does abundance of fast glycolytic fibers increase or decrease?

shift toward type IIA glycolytic fibers from type I fibers (increase in type IIA FG fibers)

• there is a decrease in slow oxidative fibers; those that still exist decrease in cross sectional area and diameter

what are astronauts doing on the ISS to minimize muscle loss

exercising (treadmill exercises)

• lots of exercise (at least 2 hours/day)

how does the distribution of bodily fluids change in space? why?

Blood flows upward, so fluid accumulates at the head and leaves the legs

• fluid to heart and head with no gravity to pull it down

• puffy face and chicken legs

what happens to the heart in space? why?

Shrinks and atrophy because the muscles are not used as much

• Decrease in arterial pressure

• Decrease in blood volume

more round shape, less work load and fluid (decrease CO)

increase blood flow affects hearing, eyes, and edema

what happens to blood vessels in space? why?

May lose some elasticity and responsiveness as they adapt to the lack of gravitational stress; atrophy

• walls become thicker (especially in head and neck because of increased blood flow) → less elasticity, atrophy (smooth muscles)

what happens to balance and inner ears in space? why?

Shifts in inner ear fluid and fluid accumulation/pressure causes disrupted balance and sometimes hearing loss

• Causes space motion sickness, includes nausea

what happens to skin? why?

Thinning of epidermis and losing elasticity because of degradation of collagen, dehydration, impaired healing

• More susceptible to irritation and rashes

• drier and ages faster because of radiation and less collagen

what happens to eyes in space?

Edema at the optic nerve can cause visual impairment and change in eye shape (flattening the back of the eye)

• swelled optic nerve

• space flight neurocular syndrome

• optic nerve squished → blind

what happens to bone structure in space? why?

Decrease in bone density -> osteoporosis because of decrease in mech stress

Disrupted balance between osteoclast and osteoblast (osteoclast activity stays the same, but osteoblast decreases)

• osteoclast = destroys boen

• osteoblast = builds bone

what is a kidney stone? why are astronauts more prone to them while in space?

Kidney stones: salts and minerals that bind together in concentrated urine

Calcium stone, because of the osteoclast activity that releases Ca2+ into the urine

• Increased formation in astronauts due to lower amounts of urine volume and higher Ca2+ excretion rate

• There is an increase in Ca2+ in the urine due to bone reabsorption -> leads to a negative calcium balance in the body

how are astronauts trying to minimize bone loss? how long does it take to recover bone density after prolonged space travel?

Exercise to minimize bone loss; takes up to 3 years if ever

• especially resistance training

• Ca2+, VfD supplements, and meds

what are some examples of psych stresses that astronauts endure?

depression, isolation syndrome, home sickness, no privacy

what are some examples of cognitive tests that astronauts have to perform regularly while in space?

winscat = general psych eval

cognition tests = 10 tests

what are some examples of interventions that people are trying to address cognitive and psychological issues?

VR simulation, anti psychotic, flight history has an impact

twins in space - body mass

significant loss of fluid and muscle mass

• initial spike because of return to fluid

twins in space - carotid diameter

space heart recovered back to normal levels

• carotid artery = delivering blood to brain

twins in space - bone AP

in space, trying to build bone then drops from injury to system (being in space)

• increased AP = more bone building

• spike upon return to earth

• relatively similar values to norm

telomeres in space

telomeres get longer in space

• reason unknown