1. Humans AND THE DISRUPTION OF CIRCADIAN RHYTHM.
WHAT HAPPENS TO THE BODY, THE MIND AND THE BEHAVOUR OF HUMANS.

2. First things first: what is the circadian rhythm?
(oops! here comes some medical science, just a little)

3. Circadian rhythms are the changes that follow a 24-hour cycle, responding primarily to light and darkness in an organism’s environment.
They are found in animals, plants and many microbes

4. These rhythms can influence:
sleep-wake cycles
hormone release
body temperature
The study of circadian rhythms is called
CHRONOBIOLOGY

5. Circadian rhythms are important in determining human sleep patterns.
The body’s master clock, or the suprachiasmatic nucleus (SCN), controls the production of melatonin, a hormone that makes you sleepy.

6. The SCN is a small group of brain cells located in the hypothalamus that:
controls the circadian cycles
influences many physiological and behavioral patterns occurring over a 24-hour period.

7. THE EFFECT OF Light on circadian rhythms.
(now that we know what it looks like and why it is there, let’s see how it works with light)

8. Light exposure to the eyes is the strongest external factor for and individual to maintain its 24-hour circadian rhythm.

9. The SCN receives information about light through the eyes.
The retina of the eye contains photoreceptors:
rods for seeing at night
cones for distinguishing colors

10. But the retina also contains specialized ganglion cells:
they are photosensitive
they project directly to the SCN, where they help this master circadian clock

11. Circadian rhythm and sleep

12. The circadian rhythm falls and rises at different times of the day.

13. A typical adult will experience the strongest desire to sleep:
in the pre-dawn hours
(2 to 4 am)
in the early afternoon (1 to 3 pm)
It may be slightly different depending on whether you are a morning or a night person.

14. When we have been awake for a long time, sleep-wake homeostasis tells us that the need for sleep is gathering, and staying awake becomes more difficult.

15. The effects of the disruption of circadian rhythm

16. When the circadian system changes due to artificial light,
mood,
learning
memory
become impaired.

17. This can be seen in
jet lag
shift work
situations.

18. When melatonin secretion goes down, because of untimely light, alertness levels increase.

19. Disruption of circadian rhythm as a result of light also causes changes in metabolism.

20. Except for light, what other factors disrupt the circadian rhythm.

21. Although light is the strongest one, it is not the only factor acting on circadian rhythm.
Exercise
Feeding schedules
Social Interaction
Stress
Pharmacology
have shown similar effects.

22. treatment

23. Dark therapy before bedtime, where light is filtered out with eyewear, is considered an effective method to:
promote earlier production of melatonin
improve sleep

24. A NEW FIELD: SCOTOBIOLOGY
(You can’t tell what on earth it means? Of course it is Greek.)
Scotos=Darkness

25. Most biological systems on the planet depend on:
Day and night change.
Seasonal changes of light patterns.

26. Photobiology
(phos=light):
The study of the role of light for essential activities such as:
Sight
Photosynthesis

27. Scotobiology: the biology of darkness.
It studies the effects of darkness on the behavior and metabolism of animals, plants and microbes.

28. It lays the foundation for understanding the importance of dark night skies for all biological species.

29. It studies the positive responses of biological systems to darkness and not merely the negative effects caused by the absence of light.

30. The presence of uninterrupted periods of darkness and their alternation of light is just as important to biological behavior.

31. Thank you US National Library of Health (www.ncbi.gov)
National Institute of Health (