Wrap-up: your badge, your glossary, what comes next
You will be able to: Review the module in five lines, check your badge and know what is coming in Module 3.
Module 2 in five lines
- Two switches decide when you sleep: the body clock (a cycle of about 24 hours) and sleep pressure (builds while you are awake).
- Light and dark have the biggest influence on the clock: light soon after waking tends to move it earlier, late-evening light later.
- Melatonin is a darkness signal; ordinary room light before bed delayed and shortened it in a lab study.
- Caffeine blocks adenosine, so you feel less sleepy, but it does not replace sleep; clearing half of it takes about 4 hours (2 to 8).
- Your chronotype shifts with age; use it to plan your day, and keep your anchor time anyway.
Your sleep score card
Your card now includes this week's nights so far. Save it as an image or copy it as text: it is made in your browser, and nothing is uploaded.
Your badges
Missing the Clock Keeper badge? Every required unit needs a tick, and the quiz needs 6 out of 8.
Glossary for this module
- Adenosine
- A chemical released by cells that helps make you feel sleepy; caffeine blocks its action.
- Body clock
- The timer in the brain, running on a cycle of about 24 hours, that sets daily rhythms of alertness, temperature and hormones.
- Caffeine cut-off
- The latest time of day you have caffeine; the NHS advises no tea or coffee for at least 6 hours before bed.
- Circadian rhythm
- A cycle in the body that repeats about every 24 hours, such as alertness or body temperature.
- Melatonin
- A hormone made in response to darkness that rises in the evening and helps time your daily rhythms.
- Receptor
- A landing site on a cell that a chemical fits into to have its effect.
- Second wind
- A burst of alertness in the evening, when the body clock is still pushing for wakefulness against sleep pressure.
- Sleep pressure
- The drive to sleep that gets stronger every hour you are awake and is released by sleep.
- The gap between your sleep timing on work days and on free days.
- Suprachiasmatic nucleus (SCN)
- The group of nerve cells in the hypothalamus, deep in the brain, that acts as the master body clock.
- Two-process model
- The idea that sleep timing comes from the body clock and sleep pressure working together.
One sentence for yourself
"The one light or caffeine habit I most want to test in week 2 is ______________________."
What is next
Module 3: A night, mapped. What actually happens between lights out and morning: the stages of sleep, why deep sleep comes early and more dreaming sleep comes later, and why brief wake-ups in the night are common. By the end of it your baseline week will be complete, and you will read it as a whole.