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