This document discusses sleep anatomy and jet lag. It describes how structures in the brain like the hypothalamus and brain stem control sleep and wake cycles. Jet lag occurs when these circadian rhythms are disrupted by traveling across time zones. The document also recounts the author's experience with jet lag upon moving from Vietnam to Europe, including feeling exhausted for several days as their body adjusted to the new time zone. Finally, it emphasizes that sleep plays an important role in physical and mental health.

1. Sleep and Jet lag
• Anatomy of Sleep
• How we fall asleep?
• What happens in this process?
• What causes jet lag?
• My experience with Jet lag.
• The importance of sleep.

2. Anatomy of Sleep
• Several structures within the brain are involved with sleep.
• Brain graphic showing the anatomy of sleep
Source: https://www.ninds.nih.gov/health-information/public-
education/brain-basics/brain-basics-understanding-sleep

3. The hypothalamus, a peanut-sized structure deep inside the brain, contains groups
of nerve cells that act as control centers affecting sleep and arousal. Within the
hypothalamus is the suprachiasmatic nucleus (SCN) – clusters of thousands of cells that
receive information about light exposure directly from the eyes and control your behavioral
rhythm. Some people with damage to the SCN sleep erratically throughout the day because
they are not able to match their circadian rhythms with the light-dark cycle. Most blind
people maintain some ability to sense light and are able to modify their sleep/wake cycle.
The brain stem, at the base of the brain, communicates with the hypothalamus to
control the transitions between wake and sleep. (The brain stem includes structures called
the pons, medulla, and midbrain.) Sleep-promoting cells within the hypothalamus and the
brain stem produce a brain chemical called GABA, which acts to reduce the activity of arousal
centers in the hypothalamus and the brain stem. The brain stem (especially the pons and
medulla) also plays a special role in REM sleep; it sends signals to relax muscles essential for
body posture and limb movements, so that we don’t act out our dreams.
The thalamus acts as a relay for information from the senses to the cerebral cortex
(the covering of the brain that interprets and processes information from short- to long-term
memory). During most stages of sleep, the thalamus becomes quiet, letting you tune out the
external world. But during REM sleep, the thalamus is active, sending the cortex images,
sounds, and other sensations that fill our dreams.

4. The pineal gland, located within the brain’s two hemispheres, receives
signals from the SCN and increases production of the hormone melatonin, which
helps put you to sleep once the lights go down. People who have lost their sight
and cannot coordinate their natural wake-sleep cycle using natural light can
stabilize their sleep patterns by taking small amounts of melatonin at the same
time each day. Scientists believe that peaks and valleys of melatonin over time are
important for matching the body’s circadian rhythm to the external cycle of light
and darkness.
The basal forebrain, near the front and bottom of the brain, also
promotes sleep and wakefulness, while part of the midbrain acts as an arousal
system. Release of adenosine (a chemical by-product of cellular energy
consumption) from cells in the basal forebrain and probably other regions supports
your sleep drive. Caffeine counteracts sleepiness by blocking the actions of
adenosine.
The amygdala, an almond-shaped structure involved in processing
emotions, becomes increasingly active during REM sleep.

5. The sleep are controlled by distinct parts in the hypothalamus,
following that, there is a circle of sleeping and awake state. This circle
is modified by two factors: sleep pressure and circadian rhythm.
https://nigms.nih.gov/education/fact-sheets/PublishingImages/circadian-
rhythms/circadian-hypothalamus.jpg
How we fall asleep?

6. Melatonin
circadian
rhythm
Adenosine
sleep
pressure
Circadian rhythm is processed by
the light – dark circle, in which
melatonin is produced when we
receive the darkness signal.
Chart: https://www.ch.ic.ac.uk/local/projects/s_thipayang/intro.html
Adenosine is produced from
when you wake up. An increase
in adenosine increases a person’s
need for sleep, also called the
sleep drive or sleep pressure
Chart: https://www.cdc.gov/niosh/work-hour-training-for-
nurses/longhours/mod2/12.html

7. https://www.physoc.org/magazine-articles/what-makes-a-good-nights-
sleep/
Sleeping and waking up depend on two parallel processes.
Falling asleep happens when sleep pressure increases until peaks at 22-23PM.
From that point, provoking awaking process, you will awake up when adenosine is
eliminated around 6-7AM.

8. Jet lag happens when sleep-wake rhythm is impacted by the change of time
zone.
In my case, it happened when i moved from Vietnam to Europe in October 2022
(6h later of time zone in Europe)

9. I arrived Paris at 4PM , but in Vietnam it was midnight. I usually sleep at
10PM. Normally, I sleep deeply at that time (maybe it is NREM sleep – non
rapid eye movement sleep), but I still stayed up late. In my experience, in one
week, I felt so tired. It looks like I was exhausted and I could not concentrate
on diurnal activities in first several days.
I will describe by chart to show you the change of the sleep pressure (the
drive to fall asleep) at the moment when I arrived in Paris.
My experience with Jet lag

10. 10PM
4PM
6 AM
10PM
4 AM
24PM
Vietnam
Paris
sleep pressure increases
continuously
As you see above, there is a change of sleep-awake rhythm since I had arrived Paris.
The yellow line shows that sleep pressure increases continuously and adenosine is
produced non-stop until I fall sleep at 10PM (time zone in Paris). But differently
with my habit, at that time, it is 4AM in Vietnam, I nearly close to time when I wake
up every day.
circadian rhythm

11. Sleep plays a important role in ours lives. During sleep,
your body is working to support healthy brain function and
maintain your physical health.
Sleep is essential to every process in the body, affecting
our physical and mental functioning the next day, our ability to
fight disease and develop immunity, and our metabolism and
chronic disease risk.
The importance of sleep