What are ciradian rhythms?

What are ciradian rhythms?

Chris Idzikowski (Director of the Edinburgh Sleep Centre) gives expert video advice on: Why do we need sleep?; How much sleep is recomended each night?; Does the amount of sleep differ between men and women? and more...

Circadian rhythms are defined as biological rhythms that run every 24 hours and that's opposed to ultradian rhythms that are faster than 24 hours or infradian rhythms that run longer than 24 hours. But basically its a 24 hour cycle and sleep and wakefulness is a 24 hour rhythm