bio rhythms Flashcards
what is a circadian rhythm
operate on a 24-hour cycle which is reset by levels of light
whats an example of this
sleep-wake cycle is an example of a circadian rhythm
whats the super charismatic nucleus role in this
The suprachiasmatic nuclei (SCN) in the hypothalamus detects the level of light present
The SCN then uses this information to coordinate the activity of the entire circadian system by either triggering sleep or telling the body to wake up
what is melatonin’s role in this
melatonin plays a role in triggering sleep by responding to a decrease in the levels of light
This explains why you may feel sleepy in a darkened cinema even when it is the middle of the day
Melatonin secretion correlates with increased feelings of sleepiness about two hours before someone’s regular bedtime
how can this change
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
what types of effects does this lead to
memory lapses
poor concentration
issues with fertility
increased risk of cancer, heart disease and diabetes
who did a natural experiment on this
siffre
what did he do/ find
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
He also stated that he had kept to his usual habits i.e. going to sleep and waking at the usual times
how does this support
supports the idea that the sleep-wake cycle has a duration of just over 24 hours and that any interference with this cycle is likely to be detrimental to functioning
what are infradian rhythms
cycles that last more than 24 hours
whats an example of this
the menstural cycle
SAD (seasonal affective disorder)
how (menstrual)
This cycle is under hormonal control 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)
how (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
who did research on SAD
rosen et al
what did they find
4 different states in the US
They found that winter SAD rates were significantly higher the more northern the state was
No correlation was found between northern/southern states and summer SAD
The highest prevalence of winter SAD was found in age groups over 35
The researchers concluded that living at a more northern latitude (longer, darker winter days) is likely to lead to SAD, particularly for older adults
what are ultradian rhythms
occur under 24-hours, best showcased in the cycles of sleep
whats an example of this
sleep cycle
stages 1 and 2
sleep escalator
Slow and rhythmic alpha waves
At this stage of sleep, it is easy to wake the sleeper; they are in ‘light sleep’
stages 3 and 4
Stages 3 and 4 consist of the delta waves of deep sleep
Delta waves are slow and deep, with greater amplitude
At this stage of sleep, it is very difficult to wake the sleeper: it may take some time for them to fully wake up during stage 3/4 sleep
stage 5
Stage 5 is REM sleep, the stage in which dreaming occurs according to research
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
who did research on the eye movement
Dement & Kleitman
what did they find
The findings showed a positive correlation between REM sleep and dreaming
The nature of the dreams was matched by their eye movements e.g.
vertical eye movements occurred with dreams of climbing ladders, watching climbers, and throwing basketballs in the air
horizontal eye movements occurred with dreams of watching people throw tomatoes at each other
