the Suprachiasmatic nucleus process

• 1.Light can penetrate the eyelids and special photoreceptors in the eye, this transfers light signals to the SCN this is our primary endogenous pacemaker and regulates our circadian rhymes such as our sleep wake cycle
• 2. In the hypothalamus - The SCN is a bundle of nerve fibres connect to the optic chiasm (eye cross area) The SCN lies just above the optic chiasm. This receives information directly about day length and light directly from this structure. Even if the eyes are closed
• 3. The SCN sends information about light to the pineal gland which contains light sensitive cells. This enables our body clock to adjust to changing patterns of day light even when we are asleep.
• 4. When light is sensed melatonin production is inhibited. Making us feel more awake.
• 5. When light level falls melatonin production increases. This induces sleep by inhibiting brain mechanisms that promote the awake state.
• Melatonin helps control your sleep cycle. The body produces melatonin just after it gets dark, peaking in the early hours of the morning and reducing during daylight hours.
• Melatonin acts on receptors in your body to encourage sleep.
• Serotonin is a melatonin pre-cursor; the pineal gland uses serotonin to synthesize melatonin.
• The healthier our levels of serotonin, the more likely it is that we'll have healthy levels of melatonin too.