biopsychology - biological rhythms Flashcards
what is a circadian rhythm ?
a 24 hour cycle
an example of circadian rhythms?
sleep/wake cycle or temperature cycle
what are exogenous zeitgebers ?
external factors that influence biological clocks.
what are Endogenous pacemakers ?
internal mechanisms that govern biological cycles.
how do endogenous pacemakers effect the sleep cycle?
Superchiasmatic nucleus is a bundle of cells located in the hypothalamus, it is above the optic chiasm which is a cross section of nerve fibers. When light is detected by the eyes the optic chiasm alerts the SCN which alerts the pineal gland to reduce release of melatonin. If its dark melatonin will increase. (melatonin is a sleep-inducing hormone.)
what are the two main exogenous zeitgebers that effect the sleep cycle?
social cues and light
how do social cues effect sleep wake cycle ?
things such as other people being awake make us think we should be awake, Social cues entrain babies after around 6 weeks infants circadian rhythms begin e.g., by putting them in dark and quiet rooms.
how does light effect sleep wake cycle ?
Light can entrain the enodgenous pacemakers, even resetting the SCN which is considered the master clock of the circadian rhythm, the sleep wake cycle. This indirectly infleuences the secretion of sleep enducing hormones
what is an infradian rhythm?
Rhythms with a frequency of less than 1 in a 24-hour period
examples of infradian rhythm?
menstrual cycle and seasonal affective disorder
what is the process of the menstrual cycle ?
Menstrual cycle is governed by changes in hormones oestrogen and progesterone.
first day of period to day before next period.
28-35 days
egg is developed via an increase in oestrogen levels and ovary releases egg
pogestorone thickens womb lining prep body for pregnancy.
if pregnancy doesnt occure womb lining sheds, egg is absorbed and released, you get your period
what is seasonal affective disorder ?
Seasonal Affective Disorder is a depressive disorder and the main symptoms include persistent low mood and lack of interest in life. It is triggered when daylight hours become shorter.
what research did DeCoursey do into endo ?
what are its strengths + limitations ?
+DeCoursey destroyed SCN in 30 chipmunks and observed them for 80 days in their NATURAL habitat to find the sleep/wake cycle disappeared.
-cross specie validity
-unethical
what research did Cambell and murphy do into exo ?
what are its strengths + limitations ?
+light may be detected by light receptors on the skin light on back on knee woke people up
-hasn’t been replicated
-hard to control E.G. light shone on back of knee may have gone onto their eyes
what research did Ralph do into endo ?
what are its strengths + limitations ?
+Ralph bred hamsters with 20-hour sleep cycle the transplanted their SCN cells into different hamsters who sleep/wake cycle changed to 20 hours
-cross specie validity
evaluate circadian rhythms
+ practical applications - shift work - we can understand when is best for employees to work so that they produce the best work - for example reduced concentration at 6 - economical implications as optimises work productivity
+folkard
- small samples in research - cannot be generalised
- poor control in studies - siffre used a lamp in the day, this light could have acted as an exogenous zietgeber and thus we dont know if the validity is good
-> PA - DRUGS
how did siffre investigate circadian rhythms ?
Siffre - caveman - wanted to study the effects of his own biological rhythms - went into a cave without light and sound - resurfaced after 2 months thinking it was mid august but it was September
his free running biological rhythms = 25 hours
what are the biological rhythms we study?
circadian - 24 hours
infradian - less that one in 24 hours
ultradian - multiple within 24 hours
what are biological rhythms governed by?
exogenous zeitgebers
endogenous pacemakers
what was Folklards research?
- group of 12 in a cave for three weeks and went to bed at 11.45pm rising at 7.45am
- over the study the researchers sped up the clocks (without PP knowing)
- so that 24hour day = 22hour
- only one PP could adjust
what does Folkwards research suggest?
suggests the existence of a free running internal biological clock that cannot be easily changed through external factors
what does siffres research suggest abou the sleep/wake cycle ?
the cycle is slightly longer than the normal 24 hours but it has been entrained by exogenous zeitgebers
outline stern and McClintocks study?
- they wanted to see how an endogenous system (menstrual cycle) may be effected by exogenous factors
- 29 women - irregular periods - samples of pheromones gathered from women via a cotton pad on their armpit
pads worn for 8 hours
pads were then frozen to be put on lip of other PP
findings of McClintock?
68% of women experienced changes to their cycle and grew closer to their odour donor
how is SAD linked to melatonin?
In the night the pineal gland releases melatonin until there is light.
since in winter there is less light, this secretion lasts longer and is thought to effect of the secretion of serotonin which has been linked to the onset of depressive symptoms
what is an ultradian rhythm?
has a frequency of more than one cycle in 24 hours
example of ultradian rhythm
sleep cycle
what are the first two stages of sleep
light sleep - easily woken - slower wave patterns and more rhythmic - alpha waves - become slower as sleep is deeper to theta waves
what is typical night of sleep
psychologist have found 5 stages of sleep and believe that they last around 90 minutes and we have around 4 a night.
Each part is a different level of brainwave activity which can be monitored by an EEG.
what are stages 3 and 4 of the sleep escalator?
slower waves - delta waves - this is deep sleep/ slow wave sleep - difficult to wake someone up at this point - amplitude of waves is greater
what is the fifth stage of sleep?
REM
WHAT IS REM SLEEP?
body = paralysed
brain activity speeds up resembling an awake brain
highly correlated with the experience of dreams
evaluate stern and McClintocks research
+ evolutionary value - advantageous for women to menstruate together and so they can fall preg at the same time. New borns can be looked after collectively. ^ survival
- too many confounding variables such as diet, stress and exercise decreases valdidity
evidence for the stages of sleep
dement - study sleep in lab - 9 people - REM was correlated with dreaming - brain activity depended on how vivid the dream - suggests REM is important for ultradian sleep cycle
PA of SAD
phototherapy - lightbox that stimulates very strong light in the morning and evening to reset melatonin levels - releaving symptoms in 60% of sufferes
who conducted research into endogenous pacemakers and the sleep/wake cycle
ralph
DeCoursey
who conducted research into endogenous pacemakers and the sleep/wake cycle
ralph
DeCoursey
what is the SCN?
superchiasmatic nucleus - tiny bundle of nerve cells located in the hypothalamus. Primary endo in humans and is influential for maintaining sleep wake cycle.
what is the optic chiasm?
area in the brain were nerve fibres from the eyes cross on their way to the visual area of the cortex
how do SCN and optic chiasm work together?
SCN is above OC and the nucleus recieves infomtion about light from this structure even whilst our eyes are closed
how does SCN and pineal gland work together
SCN passes info about light to the pineal gland. pineal gland secretes melatonin
describe endogenous explanation for the sleep wake cycle
light - optic chiasm - SCN - pineal gland - Melatonin
what is melatonin
hormone that induces sleep
evaluate the effects of endogenous pacemakers
+ research support for endo –> Ralph
- cross specie validity
+ human study - siffre
- researchcfor exogenous
- may be interactionist
evaluate the effects of exogenous zeitgebers?
- problems with raplhs research - the P.P couldve seen the light in their eyes, their eyes can still be closed and it has been replicated so not reliable
+stern and McClintocks stud shows external influences - those in artic regions manage to maintain the same sleep cycle as us suggesting that it is internal
- interactionist
what is the interactionist theory?
- it is hard to separate
- studies that do often lack validity 9siffre)
- in real life they work together
- its not sensical to study them seperatey
research into sleep cycle
dement and kleitman
what did dement and kleitman do?
- monitored sleep of 9 adults in lab
- recorded on EEG
- REM sleep was highly correlated with dreaming
- participants who work during REM had better recall of dreams
