Circadian Rhythms Flashcards
Factors affecting the circadian rhythm
- endogenous pacemaker
- exogenous zeitgeber
endogenous pacemaker
SCN (superchiasmatic nucleus) in the hypothalamus
exogenous zeitgeber
external cues from the environment that influence biological rhythms
The SCN
- gets light/dark info from the eyes
- when its dark, the SCN tells the pineal gland to release melatonin, causing us to feel sleepy
melatonin peaks…
in the middle of the night and reduces towards daytime
aim of Siffre’s cave study
to investigate how a lack of light may interrupt his circadian rhythm
Siffre lived…
in a subterranian cave for two months without daylight or clocks
results of Siffre’s cave study
- his circadian rhythm remained
- his sleep/wake cycle was just over 24h
Siffre’s cave study showed…
- the brain is able to maintain an approximately 24 cycle with endogenous cues
- but it requires exogenous cues to maintain the cycle more precisely
adenosine builds up…
in neurons during the day, and is cleared during sleep
adenosine causes you to feel…
tired
caffeine blocks…
adenosine receptors in neurons, making the body less responsive to the build up of adenosine
caffeine reduces…
feelings of tiredness
artificial lighting can be bright enough to…
prevent the release of melatonin
