Biorhythms Flashcards
Infradian rhythms
• last over a period longer than 24 hours
• they occur less than once in 24 hours
• e.g. the menstrual cycle or seasonal affective disorder
Endogenous pacemakers
internal factors controlling bodily rhythms
exogenous zeitgebers
external factors involved in controlling bodily rhythms
Menstrual cycle
- pituitary gland secretes FSH
- ovaries secrete ostrogen which stops FSH and thickens lining
- pituitary gland secretes LH which triggers ovulation
- ovaries secrete progesterone which maintains the lining
INFRARADIAN RHYTHMS- Reinberg case study
examined a woman who spent 3 months in a cave with only a small lamp to provide light
•menstrual cycle shortened from 28 days to 25.7 days
• suggests that exogenous zeitgeber (light) had an impact on her menstrual cycle
• also shows that endogenous pacemakers also control the menstrual cycle as it didn’t differ that much
Ultradian rhythms
• last fewer than 24 hours
occur more than once within 24 hours
• e.g. sleep patterns
ULTRADIAN RHYTHMS- Tucker et al
found significant differences between participants in terms of the duration of each stage.
• shows that there may be innate individual differences in ultradian rhythms.
• low ecological validity
CIRCADIAN RHYTHMS
lasts around 24 hours
e.g. sleep wake cycle
CIRCADIAN RHYTHMS- sleep wake cycle
- low levels of light (retina) (exogenous zeitgeber)
- melanopsin carries signals to Suprachiasmatic nucleus (SCN) - endogenous pacemakers
- SCN sends signal to the pineal gland
- secretion of melatonin
- induced sleep
- reverses to wake up
• sunlight appears to be the primary exogenous zeitgeber and the SCN seems to be the main endogenous pacemaker
CIRCADIAN RHYTHMS- Siffre
found that the absence of external cues (light) significantly altered his circadian rhythms
• when he returned from underground with no clocks or light he thought it was one month earlier than it was
•suggests that the 24 hour sleep wake cycle was increased due to the lack of
external cues
