About Circadian rhytm and spaceflight adaptation

1. Keeping the rhythm in space
Spaceflight adaptation and zeitgebers
Presenter:
Sumit K. Singh
ID- P0053153

2. Circadian rhythm
• ‘Circa’ + ‘Diem/Dies’ = approximately
one day
• Body Clock: Physical, Mental and
Behavioral changes following a 24hrs
cycle
• Ultradian (eating, sleep-wake) and
Infradian (menstrual cycle, hibernation)
• Is endogenous but adjusted to local
environment by external cues
“Zeitgebers” most common of which is
daylight
Franz Halberg

3. Zeitgebers
• “time giver” or synchroniser
• An environment agent or event (as
light-dark cycle) that provides the
stimulus for setting or resetting a
biological clock of an organism
• Common zeitgebers:
• Light-dark ;Temperature; Earth’s gravity;
Eating- drinking patterns; Social interactions;
Exercise, etc.
Zurgen Aschoff

4. Disturbances in circadian rhythms, sleep and
performance in space

5. Physiological deconditioning in the space
• Three different physiological systems: cardiovascular,
vestibular/sensory-motor, and musculo-skeletal
• First two represent immediate responses that develop within minutes
or hours after exposure to microgravity
• The effects on the musculo-skeletal system is slow ( 𝛼 duration of
stay)
• Interfere with a healthy return to Earth if no countermeasures are
applied

6. Pre-adaptation to shiftwork in space
• Different zeitgebers ensemble
• Adjustment to substantially different work-rest conditions
• Sleep-wake cycle will possibly be shifted prior to launch towards the
schedule of the inflight duty-rest cycle
• Adjustment speed for several body functions may be slower than for
the sleep-wake cycle, causing a desynchronization between internal
and external time systems
Acta Astronautica Vol. 29, No. 8, pp. 593-599, 1993

7. Physiological effects of circadian disruption
in space
* Source of Images used here is Google Images

8. Disruption conti.….
*Advances in Physiology Education Published 1 September 2013 Vol. 37 no. 3, 220-226

9. What happens when the astronaut returns to
Earth?
Astronauts Lisa Nowak, Michael Fossum,
and Piers Sellers from STS-121 mission
 The heart is smaller and weaker
 The vestibular, or balance, system has become used to a
new set of signals
 Body fluids are diminished
 Muscles have atrophied
 Bones have weakened
“Experiences that make a space journey more
memorable”
o Space Sickness
o Disorientation
o Chipmunk faces
o Growing a couple inches taller
o What’s sleep?
o Nothing tastes good up here!

10. Countermeasures and treatmentsToimproveastronauts’
circadianrhythmsandsleep
Light therapy:
1. Bright light and dark goggles are used to
enhance or minimize
2. Short wavelength light (~460 nm to 512
nm) effective
Work-rest schedule optimization
Drug therapy:
Sleep medications (Hypnotics eg. Zolpidem),
Fludrocortisone to raise plasma vol., ….
Exercises:
Use of treadmill exercise with LBNP, cycle
ergometer, strength training devices,
electrical stimulation etc.
Postural muscle loading suit , LBNP suits,
water/salt supplements

11. Some other facts ….
• Light is the strongest zeitgebers of all. Role of gravity couldn’t be
established.
• Back and abdominal pain are commonly experienced with no clear
cause
• Crew Altitude Protection Suit (CAPS) prevents ebullism at pressures
as low as 2 kPa (15 Torr)
• Exposure to long-term reduced gravity causes reduction in muscle
mass and strength, especially in the lower extremities (legs

12. Inference & Future prospects
• Little data on the manifold effects of living in space
• Environment of space is still largely unknown
• Very limited in-flight studies have been conducted to evaluate circadian
and sleep impacts
• Very little research on crew selection process in relation to the interpersonal
influences
• Off –world colonization (eg. MARS Mission): need to have more subjects
like children, younger ones & elderly; at present only rigorously tested
humans
• Future technologies such as artificial gravity and more complex
bioregenerative life support systems

13. References:
• Google images
• NASA- HRP (Human Research Program)
• Scientific articles:
• Acta Astronautica Vol. 29, No. 8, pp. 593-599, 1993. Pre-adaptation to
shiftwork in space
• Advances in Physiology Education Published 1 September
2013 Vol. 37 no. 3, 220-226 DOI: 10.1152/advan.00035.2013. Space
physiology within an exercise physiology curriculum

14. That’s All Folks!
Buzz Aldrin on the Moon (July 1969)