biological rhythms Flashcards
what is a biological rhymth?
- change in body processes or behaviour in response to cyclical changes within environment
what are the 3 biological rhythms?
- infradian
- circadian
- ultradian
what is an infradian rhythm?
- biological rhythm that lasts longer than 24 hours + can be weekly, monthly, annually
- eg hibernation, menstrual cycle
what is a circadian rhythm?
- biological rhymth subject to 24 hour cycle which regulate number of body processes
- eg sleep wake cycle
what is an ultradian rhythm?
- biological rhythm with duration of less than 24 hours
- eg sleep stages
what are biological rhythms influenced by?
- internal body clock (endogenous pacemakers)
- external cues in environment (exogenous zeitgebers)
what are endogenous pacemakers?
- what regulate many of our biologicla rhythms
- eg influence of SCN on sleep wake cycle
what are exogenous zeitgebers?
- affect and maintain our biological rhythms
- eg influence of light on the sleep- wake cycle
endogenous pacemaker
what is the most important pacemaker? and where is it?
SCN in a cluster of nerve cells in the hypothalamus
why is the SCN the most important pacemaker?
- generates bodys circadian rhythms
- ‘masterclock’ that links brain regions that control sleep + arousal
how is the SCN the most important pacemaker?
- it lies above optic chaism
- recieves info about light
- continues when eye closed
- enables biological clock to adjust changing patterns of day light when asleep
how do the pineal gland and SCN work together?
- SCN passes info on day length + light to pineal gland
- during night-> pineal gland increases production of hormones melatonin (induces sleep)
- in the morning-> melatonin levels decrease, feel awake
evaluation
what supporting research is there from animal studies?
- Decoursey: destroyed SCN connections in brains of 30 chipmunks. sleepwake cycle disappeared and at end of study lots killed by predators
evaluation
what does animal studies suggest about the role of the SCN?
- SCN clearly is important in sleep-wake cycle as if destroyed they were killed
evaluation
what are the issues with animal studies?
- unethical- no consent + were killed
- cannot extrapolate to humans as brains are structurally + functionally different. we’re more complex
what are the 2 exogenous zeitgebers?
- light
- social cues
how is light a EZ?
- time giver
- can reset the body’s main EP (the SCN)
- maintains the sleep wake cycle
- light resets the internal biological clock each day
- receptors in SCN are sensitive to changes of light and use this info to synchronise the activity of the body’s organs and glands
what research is there for light as a EZ?
- Campbell and Murphy
- woke 15 ps at various times + light pad shone on back of knees
- managed to produce deviation in sleep wake cycle upto 3 hours
what does the research support for light for EZ show? + counter
- not just the optic nerve can detect light and send it to the SCN
- light is important EZ
- counter-> not well controlled, unreliable
how are social cues an EZ?
- in infants, circadian rhythms (sleep wake) begin from 6 weeks + most babies entrained by 16 weeks
- routine imposed by parents are likely to be key influence eg meal times/ bed times
what is a counter of social cues?
rely more on food rather than sleep wake cycle
evaluation
do EZ’s have the same effect in all environments?
no
- eg in the Artic circle theres very little darkness in summer and very little light in winter yet inutis have similar sleep pattersn all year around
- suggests EZs like light have little influence in some cases as sleep/wake cycle remained same despite little light
counter-> extradorinary circumstances + cannot be generalised to everyone around the world, so tells us little about EZs influence/ effect on worldwide scale
what evidence challenges the role of EZs?
- Miles et al
- blind man from birth having abnormal circadian rhythm of 24.9 hours despite exposure to social cues sleep/wake couldnt be adjusted
- suggests role of EZs have minimal effect on resetting biological rhythms + EPs more dominant
counter-> use of case study evidence is highly unique so cannot be generalised to whole population as other situations wouldnt be same eg abnormal circadian rhythms/blind
what is the problem with researching EZs and EPs in isolation?
- total isolation studies are extremely rare + nearly impossible to conduct
- sleep/wake is interactionist system. in most real life situations EPs and EZs work together
- reductionist to study like this, have to study hollistically. its unrealistic and unbeneficial as they interact
