Biopsychology- circadian, infradian and ultradian rhythms Flashcards
Define circaidian rhythms
Operate on 24 hour cycles and are reset by light
Give an example of circadian rhythm
The sleep wake cycle
Can circadian rhythms be altered?
Shift work and jet lag have been found to lead to the desynchronization of circadian rhythms and can lead to adverse cognitive and physiological effects e.g. memory lapses, poor concentration, issues with fertility, increased risk of cancer, heart disease and diabetes
Give an example of a study which is evidence for alteration of circadian rhythms
Siffre (1973) -spent two months in a cave deprived of light and sound
,When Siffre emerged from the cave he found that his circadian rhythm remained between 24-25 hours
Define infradian rhythms
Cycles that last more than 24 hours
Give 2 examples of infradian rhythms
-The menstrual cycle
-Seasonal affective disorder (SAD)
Outline the menstrual cycle
-This cycle is under hormonal control (endogenous pacemakers) in biological females
-It occurs roughly every 28 days
-Rising oestrogen levels cause an egg to be released from an ovary
-The egg travels down the oviduct to the womb
-Rising progesterone levels thicken the lining of the womb
-If the egg is not fertilised (by sperm cells) the lining is shed (menstruation)
Outline SAD
-SAD tends to hit people during the winter months when the days are darker and longer
-During winter months more melatonin is secreted which may result in higher levels of depression or a generalised low mood
-Serotonin is implicated in the sleep-wake cycle (it has been linked to melatonin production) so disrupted levels of this neurotransmitter is likely to lead to imbalances in mood
Define Ultradian rhythms
Cycles that occur in less than 24 hours
Give an example of ultradian rhythms
The human sleep cycle
Human sleep cycle:
-1.___minute cycle
-2.___ stages
-up to 3.___ full cycles
1.90
2.5
3.5
What happens during the 1st and 2nd stage?
-Light sleep
-Muscle activity slows down
-Occasional muscle twitching
-Alpha waves
What happens during the 3rd stage?
-Deep sleep
-Delta waves (greater amplitude)
What happens during the 4th stage?
-Deep sleep
-Rhythmic breathing
-Limited muscle activity
-Delta waves
What happens during the 5th stage?
-REM sleep
-Dreaming
-The central nervous system is ‘cut off’ (effectively paralysing the body) as dreaming occurs - thought to prevent people from acting out their dreams
-REM stands for ‘rapid eye movement’ - the eyeballs are active during this stage of sleep, indicating that dreaming is taking place
-Brain activity speeds up during REM sleep, with brainwaves showing similar levels of energy to the awake brain
