Flashcards in Assignment - Part B Deck (20):
How is studying the
effects of weightlessness on
astronauts helping us to understand
the aging process?
As the effects of weightlessness on astronauts is very similar to the aging process.
can help elderly lead healthier more active lives
Why does microgravity affect bone strength?
As there is no load bearing on bones they begin to deteriorate. productivity of oestoblasts decreases, demineralisation occurs
With respect to muscles, what is "disuse atrophy"?
This occurs when muscles are not used frequently, causing them to weaken.
At what time within the 24hr period, does melatonin secretion peak in humans?
Between 2am and 4am, and is low at 12pm
Cortisol is a specific hormone secreted by the adrenal cortex. It is also known as one of the "stress hormones".
What is the diurnal pattern of cortisol secretion in humans?
peaks at 6am - 8am and is lowest at 12am
What are the four
signs/symptoms of space
One of the more serious adverse effects of weightlessness is fluid redistribution. Why does fluid redistribution lead to dehydration?
As central baroreceptors, sense increase in upper body fluid. Thus, brain instructs body to excrete fluids.
Upon returning to Earth, astronauts are often overwhelmed by dizziness and vertigo and are unable to maintain their balance. Why?
As mechanoreceptors in the inner ear do not recieve the same stimulus as in space. Thus, have issues when returning to earth.
What happens to the size of the right and left ventricles of the heart during the first day of space flight?
Right --> decreases by 35%
Left --> increased by 20%
Why would facial oedema occur in humans during periods of weightlessness?
Due to fluid re-distribution.
What are the
physiological causes G-LOC?
increased G force pushes blood away from head, brain and eyes exhaust their supply of glucose and oxygen and can function
What are the initial physiological symptoms/signs a person will experience just before G-LOC?
Greyout, loss of vision (tunneling) then blackout. In which you are conscious but have a loss of vision, this if followed by passing-out.
At what range of positive G-force can G-LOC occur?
+2G to +6.5G
What causes grey-out?
Lack of vital nutrients to eyes (glucose and oxygen).
How does positive pressure breathing assist in prevention of G-LOC?
Increases pressure in your thoracic cavity, and pushes oxygenated blood to head.
What are the symptoms of red-out?
Loss of vision and only see red.
What causes red-out?
Excessive negative G-force, blood rushes to the head.
lower eyelid coming up and covering eyes
What is the Valsalva L1 Manoeuvre?
exhaling violently while keeping mouth and nose closed
Redouts are potentially dangerous and can cause ....................in the eyes and..................................within brain tissue.
1. Retinal Damage
2. Hemorrhagic stroke