Biorhythms Flashcards
(17 cards)
Biorhythms
any internal processes that run on a cycle
3 main types of biorhythms
Circadian (around a day)
Ultradian (more than one cycle a day)
Infradian (less that one a day )
Endogenous Pacemakers
any internal mechanism that regulates any biorhythms can be a part of the brain, a gland that secretes hormones etc
Exogenous Zeitgebers
any external mechanism that regulates our biorhythms, usually work by triggering the EPs e.g light, temp, socio-cultural aspects
The Suprachiasmatic Nucleus (SCN)
- tiny cluster of nerve cells in the hypothalamus
- responsible for circadian rhythms
- regulates other regions of the brain needed for sleep an arousal; controls other bio-clocks
- SCN neurons synchronise with each other, keeping target neurons around the body coordinated; only EP that does this therefore others rely on it for timekeeping
- regulates the melatonin in the Pineal Gland
How does the SCN link to EZs
light -> light enters eye -> travels along optic nerve to the SCN -> light readjusts the bodyclock -> puts us in synch with the outside world and ‘resetting’ the SCN each day
Pineal Gland
- produces and secretes melatonin (increased levels make you tired)
- kept informed by SCN - when light hits eye/travels to SCN, SCN then tells pineal gland to slow prodiction of melatonin so you wake up and vife versa
- because both are dependant on light, it means these EPs are dependent on EZs in order to synch with the outside world
Light
- SCN depends on light, resetting each day to stay on synch with the outside world
- Light detecting cell in retina detects brightness, and resets SCN/body clocks
- Vital protein = melanopsin; found in some retina cells, which carry signal to SCN
Social Cues
- e.g mealtimes, social activities e.g siesta
- evidence from jet lag = Kein and Wegman; jet lag time reduces the sooner and more often travellers adjust to social cues of their destination; eating times etc
- eating at correct times links to digestive system, which helps reset pacemakers too
Biorhythms AO3
EPs and Ezs
✔ Morgan’s Hamsters - support for EPs
- bred humans to have circadian rhythyms of 20hrs instead of 24 hours
- then transplanted their SCNs into non-mutant hamsters
- found the non-mutant hamsters immediately adopted the 20hr cycle
Therefore suggests the SCN is responsible for circadian rhthyms
Therefore supporting the role of EPs in biorhythms
✔ Kate Aldcroft - desynchronisation
- spent 25 days in a controlled lab with with no EZs
- she played the bagpipes twice a day, at what she believed was the same time each day
- after 25 days her temperature rhythym was 24hrs, but sleep-wake cycle was 30hrs free running
- this means she’d be wide awake but cold, then too warm to sleep. This desynchronisation is akin to jetlag
- her bagpipe playing times also got later and later each day
Therefore supports the importance of EPs - they maintain biorhthyms.
✔ Michael Siffre - support for importance of EZs
- French geoligist who spent prolonged periods in isolation in caves. Two months in a cave in the Alps; 6 months in a texan cave
- provides support for link between EP and EZ
- in the cave he had no EZs; no natural light, no clocks etc
- his biorhythyms desynchronised; sleep wake cylcle was generally consistent at 25 hours, but he had some fluctuations up to 48 hours
- his body temp cycle extended to 26-28 hrs causing massive desynchronisation
∴ EPs are capable of keeping the human body functioning, but cannot keep the body’s biorhythms in synch - they free run and de-synchronise
∴ EZs are vital not for survival, but for regulation - they keep the human body running at its most efficient
✔ Folkard
- 12 people lived in a cave for 3 weeks with no EZs except a clock
- they were told to rise and go to bed at set times
- after a few days, unbeknownst to the ppts, the clock was sped up meaning 24 hrs only took 22hrs
- only 1/12th went with the clock - the rest stuck to their own biorhythms suggesting EPs have more control than EZs
- but once it was over it only took a few days to resynchronise thanks to EZs, suggesting the importance of EZs
RWA - Jet Lag
- Herxheimer found in a meta-analysis that taking melatonin near to bedtime at your destination is effective in resetting biorhythms, but taking it at the wrong time can delay adaptation
∴ research into biorhythyms has helped; combat issues such as trans-continental travel
✘ Methadological issues
- Czeisler; found that he could alter ppts circadian rhythms up to 28hrs and down to 22 hrs just by using a dim artificial light
- this is an issue; all EZ deprivating studies have removed natural light, but made the assumption that natural, but made the assumption that artifical light cannot function as an EZ - this turns out to be incorrect
∴ may be that all EZ deprivation studies have returned invalid results due to a flawed methodology
Circadian Rhythyms AO3
✔ Hughes support importance of light
- tested circadian hormone release in 4 ppts stationed in Antartica
- at the end of ‘summer’ down there, cortisol levels were normal; highest as they awoke + lowest as they slept
- then followed 3 months of darkness
- cortisol levels now peaked at noon
- suggests not only the importance of light in keeping hormone rhythms stable, but also how extremes of light can effect huge changes
- (however similar study in Arctic but found no changes)
✘ Individual Differences - Czeisler
- early research (Siffre etc) utilised artificial light, assuming it wouldn’t have an effect on circadian rhythms
- however Czeisler was able to manipulate circadian rhythms
RWA - Chronotherapeutics
- timing of administration can affect drug impact
- if drugs are more effective at certain times, or if the body is more at risk at certain times, it can be vital to time the administration of the drugs properly
- e.g heart attacks are most common during morning hours after working but medication taken first thing in the morning it won’t take effect for a couple of hours
- new delivery systems have been invented where the drug is administered before a person goes to bed, but doesn’t release until 6am
∴ more effective
∴ research into biorhythms had led to more effective drug treatments
Endogenous Pacemaker functions in menstrual cycle
Infradian
- pituitary gland releases hormones which stimulates release of an egg and release of oestrogen
- once egg ripens, progesterone secretes which causes blood supply to the womb to increase
- 2 weeks after ovulation, if there is no pregnancy, progesterone levels reduce and womb lining break down
- Refinetti found women experience cycles as short as 23 days or as long as 36 days, with an average of 28 days
EZs in menstrual cycle
infradian
- calorie intake (extreme reduction)
- [menopause, pregnancy, medical contraceptives]
- anaemia
- stress
- extreme excercise
Infradian rhythms AO3
✔ Support for Menstrual Cycle and the role of EZs;
- Russell et al; noted the McClintock effect - that women of child bearing age living in proximity and not using oral contraceptives often find their cycles align
- took sweat from one group of women, applied it to the lips of a second seperate group of women
- their cycles aligned
∴ the EPs that cause the menstrual cycle appear to give pheromones that act as EZs to other women. it could not have been social cues, as the women never met.
✔ Support for the impact of menstrual cycle on mate choice;
- as the focus of the mentrsual cycle is to get pregnant, it makes sense that female preferences vary depending on where they are in their cycle
- Penton-Voak et al; women prefer slighlty feminised versions of male faces for long term relationships … but for short term sexual relationships during the high conception risk phase of theuir cycle, they prefer more masculinated faces
- these males are more likley to have higher testosterone levels, which suppresses the immune system. If a male is healthy depsite this, his immune system must be efficient, so good genes to have
∴ this suggests that mentrual cycle enables women to select differently depending on certain conditions. When conception is more likely, they opt for the best genes. When slightly less likely, they focus on ‘kind’ aces, which may help with parental care
Miller
- fertility is vital in a man finding a women attractive… yet there is no way of knowing how fertile a woman is at a particular time
- it is suggested that women at the most fertle point are somehow more attractive to men
- Miller et al tested this in a lap dancing club??? Women in the fertile stage received almost X2 as many tips as women who weren’t
- this may be due to phereomone release subconsciously picked up by males, or women feeling more attractive so dancing more attractively
∴ suggests that fertility is important to men, even on a level which cannot physcially be measured.
Stages of Sleep
Stage 1; Alpha waves
- light sleep, slowing of muscles, hr, breathing, occasional hypnagogic twitch
Stage 2; Theta waves
- hr, breathing slows etc slows further, temp drops
Stage 3; Core/Slow wave sleep begins
- delta waves begin
Stage 4; Deepest sleep, long slow delta waves
- hr,br very low, little body movement, growth hormone released
Then back to stage 2
REM Stage;
- brainwaves returns to B waves, rapid eye movement. HR, BP increase, all to near walking levels… but muscles are relaxed and connot move
- then back to stage 2, then through again
Ultradian Rhythms
✘ Tucker - Individual differences in sleep stages
- studied ppts over 11 consecutive days and nights in a controlled setting
- found large individual differences, especially for slow wave sleep (stg 3 and 4)
- because the environment was controlled, it suggests a dispositional factor, rather than an environmental one
∴ not everyone experiences the stages of sleep in the same way
✘ Ohayon - Experience of sleep stages change over time
- meta-analysis of 65 studies on lifespan changes in sleep
- ppts ages 5-102 yrs
- key findings
- total sleep decreased over lifespan, from 470 minutes at 5 yrs to 370 minutes at 70yrs
- deep NREM; 24% of sleep at 5 yrs -> decreased to 9% at 70yrs
- REM; 25% of total sleep at 5yrs -> decreased to 19% at 70yrs
∴ as the body changes and ages, the way we sleep changes. This has an impact on how we live out lives
