1. Melatonin and Sleep

3. The Pineal Gland
A tiny cone shaped gland located in the center of the brain, about the size of a grain of rice
It is present in almost all vertebrate species
Produces a hormone that regulates sleep patterns in both seasonal and circadian rhythms.

4. Circadian Rhythms
Humans are adapted to live in a 24- hour cycle and have rhythms in behaviour that fit this cycle, known as circadian rhythms
They can continue even if a person is placed experimentally in continuous light or darkness because of an internal system used to control the rhythm.

5. Circadian Rhythms
Circadian rhythms depend on two groups of cells in the hypothalamus called suprachiasmatic nuclei (SCN).
When light enters the eye (when you open your eyes in the morning ) and hits the retina, the information travels to the SCN via the optic nerve.
The SCN signals your internal clock that it is time to be awake
It also signals the hypothalamus to cause the release of hormones, such as cortisol, to increase blood sugar and get you ready for your day

7. Melatonin Melatonin is a hormone released by the pineal gland
(It is actually derived from the neurotransmitter serotonin)
Melatonin levels are high in the evening when it gets dark.
Melatonin levels decrease throughout the night and is low at dawn

8. Melatonin Sleep-Wake Cycle
High melatonin levels => feelings of drowsiness and promote sleep through the night.
Low melatonin levels => waking up at the end of a nights rest

10. Other effects of Melatonin
Linked to the drop in your body’s core temperature during sleep (though drop in temperature is also due to decreased movements which generate heat)
There are melatonin receptors in the kidney. This may be responsible to the decrease in urine production throughout the night.
Melatonin has a role in regulating the hypothalamus which ultimately effects other hormonal secretions.

12. Melatonin
The hormone is rapidly removed from the blood by the liver, and so its concentration in the blood rise and fall in response to changes in secretion.

14. Melatonin and teenagers
Melatonin levels in the blood of teenage rise naturally later at night than in most children and adults
This is why many teems may have difficulty going to bed early to get enough sleep.
It may help to dim the lights as bedtime approaches, and to get into bright light as soon as possible in the morning

15. Jet Lag Experienced when crossing time zones during air travel.
Symptoms: difficulty in remaining awake during daylight hours and sleeping during night in the new time zone
Also fatigue, irritability headaches, indigestion

16. Why?
The SCN and the pineal gland are continuing to promote a circadian rhythm to suit the timing of day and night according to your original time zone
Only last a few days. The SNC will receive the information of “light” and readjust to the new time zone.
Melatonin can be taken orally to reduce jet lag and promote sleep

17. The Importance of Sleep
Why is sleep important?
Not only is melatonin high during sleep, but also GH, testosterone and prolactin – this is an important time for growth
Sleep allows for repair and rejuvenation of body tissues.
Allows for the brain to process information from the day, replaying the days events and converting short term memory to long term.

18. Sleep Cycle