Circadian Rhythms Flashcards
circadian rhythms
a pattern of behaviour that occurs or recurs approximately every 24 hours set and reset by environmental light levels
what are the circadian rhythms synchronised with
the suprachiasmatic nuclei which if found in the hypothalamus
The SCN uses information about light levels to
coordinate the activity of the entire circadian system e.g
hormones, body temperature
types of circadian rhythm
the sleep wake cycle
core body temperature
hormone production
The sleep wake cycle
- light and darkness detected by eye
- sends message to suprachiasmatic nucleus
- SCN uses this info to coordinate the circadian system
light
Light provides the primary input to this system, acting as the external cue for sleeping or waking
when awake for a long time what does the body tell you
homeostasis tells the body that there is a need for sleep because of energy consumption
when is your strongest sleep drive
2-4am
1-3pm
homeostatic drive- sleep wake cycle
more energy is used throughout the day so homeostatic drive increases to it maximum in late evening
core body temperature when is it at its lowest and highest
4: 30am lowest
6: 00pm highest
body temp linked to sleep
- sleep occurs when the core temperature begins to drop
- body temp begins to rise during last hours of sleep promoting feeling of alertness
hormone production- light
is set and reset by light levels
research support on effect of external cues
Siffre (1975) found that the absence of external cues significantly altered his circadian rhythm When he returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was
suggests his 24 hour sleep wake cycle was increased by lack of external cues
evaluation weakness
indvidual differences
Duffy 2001 found innate differences in circadian rhythms as ‘morning people’ prefer to rise and go to bed early whereas ‘evening people’ prefer to wake and go to bed later
