Circadian rhythms

Question 1

What is a circadian rhythm?

Answer 1

A pattern of behaviour that occurs or recurs approximately every 24 hours + is set and reset by environmental light levels

Question 2

What is an example of a circadian rhythm?

Answer 2

The sleep-wake cycle

Question 3

How do circadian rhythms work?

Answer 3

Driven by our body clocks found in all the cells of the body + synchronised by the master circadian pacemaker = the suprachiasmatic nuclei (SCN) - found in the hypothalamus

Question 4

What is the role of the suprachiasmatic nuclei?

Answer 4

The pacemaker constantly must constantly be reset so that out bodies are in synchrony with the outside world. Light provided the primary input into this system, setting the body clock to the correct time in a process termed photoentrainment

Question 5

How does light help coordinate the circadian rhythms?

Answer 5

Light sensitive cells within the eye act as brightness detectors, sending messages about environmental stimuli light levels to direct to the SCN
the circadian rhythm

Question 6

How does the sleep-wake cycle work?

Answer 6

Light and darkness are the external signals that determine when we need to sleep/wake up
The circadian rhythm dips and rises at different times in the day - our strongest sleep drive usually occurs on two ‘dips’ 2-4 am and 1-3pm (post lunch dip)
These dips are less intense is we have had sufficient sleep