Circadian Rhythms Flashcards
What are circadian rhythms?
Biological changes in the way our biological system behaves- sometimes referred to as our body clock. These rhythms last around 24 hours.
What is an example of a circadian rhythm?
The sleep-wake cycle.
What is the biological rhythm driven by?
Internal biological clocks (endogenous pacemakers) and external changes in the environment (exogenous zeitgeibers).
What is photoentrainment?
The fact that light provides the main input for the body clock.
Describe how light affects the body clock.
Light sensitive cells in the eyes detect brightness and send messages too the SCN which then uses that information to co-ordinate activity in the circadian system.
Describe the sleep-wake cycle.
Light and dark are external cues for sleep/wake.
There are dips and rises at key times: strongest sleep-drive in two dips 2-4am (lowest body temp) and 1-3pm (sleepy).
Cycle is under homeostatic control which tells us to sleep if we are awake too long.
Describe Micheal Siffre’s Cave Study
-Self-styled caveman who has spent several extended periods underground to study the effects on his own biological rhythms.
- Deprived of exposure to natural light and sound but access to adequate food and drink, re-surfaced in September 1962 after two months in the cave and believed it was August.
- A decade later he performed a similar feat but for 6 months.
- Both cases: ‘free running’ biological rhythm settled down to one that was just beyond 24 hours though he did continue to fall asleep and wake up on a regular schedule.
