Types of Biological Rhythm

Biopsychology – Biological Rhythms

In this course, Dr Halstead (University College London) explores biological rhythms. In the first lecture, we think about the three main types of biological rhythm: infradian, circadian and ultradian. In the second lecture, we think in more detail about circadian rhythms, specifically the sleep-wake cycle. In the third lecture, we think in more detail about infradian and ultradian rhythms, specifically the sleep cycle and the menstrual cycle. Next, we think about the impact of rotating shift work on circadian rhythms, reviewing Czeisler and colleagues’ 1982 study. In the fifth and final lecture, we think about some key ways of reducing the impact of jet lag on circadian rhythms.

Types of Biological Rhythm

In this lecture, we think about the three main types of biological rhythm, focusing in particular on: (i) infradian, circadian and ultradian rhythms; (ii) defining an endogenous pacemaker as an internal process or structure which regulates a biological rhythm; (iii) the suprachiasmatic nucleus, which is influential in maintaining the sleep-wake cycle; (iv) defining exogenous zeitgebers as external factors which impact internal processes, such as light; (v) the fact that infradian rhythms last longer than 24 hours, circadian rhythms last approximately 24 hours and ultradian rhythms last less than 24 hours; (vi) an example of an infradian rhythm being the female menstrual cycle, which is regulated by hormones and usually lasts approximately 23-36 days in humans; (vii) the sleep-wake cycle as an example of a circadian rhythm in humans; (viii) stages of the sleep-wake cycle, specifically looking at Rapid Eye Movement (REM) and non-REM sleep.