Biological Rhythms Flashcards
What are circadian rhythms
biological rhythm which occurs within 24 - hour cycle
Endogenous Pacemakers
. Internal mechanisms that govern bio rhythms
. Most important is SCN - closely linked to pineal gland (master clock)
^ E.g: receives info about light via optic nerve - sends signal to pineal gland = increased melatonin at night
Exogenous Zeitgebers
Environmental events that are responsible for resetting bio clock of an organism
Siffre study
Free - running circadian rhythm
. Spent 6 months in cave with no natural light or other potential EZ’s
. Body clock remained regular cycle around 25hrs
^ suggesting EP for sleep wake cycle is free running but needs EZ’s to keep 24 hour day night cycle
Evaluation of Siffre study
. Lacks ecological validity
. Study had artificial lighting
Evaluation of Circadian Rhythms
Research support - EZs
^ Siffre study findings
Individual Differences
. may be innate differences in circadian rhythms - differences between morning and evening ppl
Research support - EPs
. Morgan bred hamsters so had circadian rhythms of 20hrs. SCN neurons transplanted into normal hamsters - displayed some abnormal rhythms
. Proves EP important for bio
Infradian Rhythms
Biological rhythm that lasts longer than 24hrs. E.g: menstrual cycle
Menstrual Cycle
. Governed by EP, controls release of oestrogen and progesterone - leads to egg release
. Pheromones released from now sexually active women
. Attracts potential mates and synchronises menstrual cycles of others
^ synchronising infradian rhythms - example of role of pheromones as an EZ
Explaining synchronisation (IR)
. Women with synchronised menstrual cycles will give birth at same time
. Assist eachother in rearing and nursing kids - increases survival chances
. McClintock = male pheromones reset womens bio clock - have much shorter menstrual cycles
Evaluation of Infradian Rhythms
Research Support
. Swab taken from donor’s armpit daily
. Rubbed onto upper lip of other women who had different cycles to donor
Findings = 4/5 women in experiment had synchronised menstrual cycles within day of donor
Research support for McClintock
. Women who work with men have shorter menstrual cycles
Ultradian Rhythms
Bio rhythm that have more than one cycle throughout 24 hour day
REM (UR)
Rapid eye movement stage of sleep in approx 90-110 min cycles, repeated continuously throughout 7-8hr sleep cycle
Evaluation of Ultradian Rhythms
Research Support
. Further evidence 90-110 min cycle can also be seen in many other physiological functions
^ such as eating and drinking
Individual Differences
. Significant differences between participants in terms of duration of each stage
^ may be innate individual differences in ultradian rhythms
Ecological Validity
