biological rhythms Flashcards
what are biological rhythms
cyclical changes in the way that biological systems behave
what are all biological rhythms governed by
endogenous pacemakers and exogenous zeitgebers
what are the 3 biological rhythms
circadian
ultradian
infradian
how long are circadian rhythms
about 24hrs
how long are ultradian rhythms
less than 24hrs
they repeat more than once every 24hrs
how long are infradian rhythms
more than 24hrs can be days, weeks, months, annual etc
example of circadian rhythms
sleep-wake cycle
core body temperature
hormone production
they are all interrelated
example of ultradian rhythms
the stages of sleep
basic rest activity cycle (brac) which is around 90mins
appetite
example of infradian rhythms
female menstrual cycle (monthly rhythm)
what are endogenous pacemakers
the internal body clock which regulates biological rhythms eg effects of suprachiasmatic nucleus
what are exogenous zeitgebers
external/environmental cues that entrain our biological rhythms eg light which confuses the SCN
what does entrain mean
to determine or to modify
what is photoentrainment
when light provides input to the body clock
what do light sensitive cells in the eyes detect and what do they do
detect brightness and send messages to SCN
what does the SCN do with the info sent from brightness receptors
uses that info to coordinate activity of the circadian system
where is the SCN located
in the hypothalamus
according to the sleep wake cycle what time do we wake up
around 7am
according to the sleep wake cycle what time do we feel most alert
around 11am
according to the sleep wake cycle what time do we have a dip in alertness
in the afternoon
according to the sleep wake cycle what time do we got to sleep
around 11pm
according to the sleep wake cycle what time do we feel least alert
around 2am
what is the circadian rhythm for hormones
hormone release at similar times each day
what is the circadian rhythm for body temperature
body temp rising in the evening and falling during the night
Explain how the sleep-wake cycle follows a circadian rhythm?
A circadian rhythm is a biological rhythm that lasts for 24 hours.
Each day we all have a time when our body naturally wakes up, we have a burst in energy during mid-morning, we have a slump in energy during the afternoon, we fall asleep at a similar time in the evening and we are at our lowest alertness around 2am
then the cycle starts again and repeats for the next day. Therefore, we all have a sleep/wake cycle that repeats every
24 hours.
when is our body temperature at its lowest
around 4am
when is our body temperature at its highest
around 6pm
what is chronotherapeutics
Chronotherapeutics allows people to take drugs which then aren’t effective until necessary, hours later.
A Chronotherapeutics was developed using knowledge of the circadian rhythm.
what does chronotherapeutics assume about people
that they all have the same circadian rhythm sleep wake cycle
what type of study did duffy conduct
controlled observation
what did duffy srudy
She studied differences in people’s sleep/wake cycles for a month.
she conducted a controlled observation looking into people’s sleep/wake cycles for a month.
duffys findings
She found that other circadian rhythms like body temperature synchronised with people’s sleep/wake cycle.
She found two types of people: “morning people” who go to bed earlier and wake up earlier, and “evening people” who go to bed later and wake up later.
She found individual differences in people’s circadian rhythms.
Question 4: Meera has low blood pressure which is worst in the morning. If she gets out of bed too fast or doesn’t do gentle movements first thing, she can become very light headed and even pass out. There are drugs that Meera can take, but if she took them the night before, their effects would have vanished by the time she woke up in the morning.
hronotherapeutics uses the knowledge of circadian rhythms to adjust the timing of drug activity. It means that the action of drugs can be delayed until the time of day when they would be most effective. For Meera, the drug needs to start working around the time she wakes up in the morning. That means that by using chronotherapeutics, Meera can take the drug at night before she goes to bed, and the drugs action will be delayed until the early hours of the morning.
what are the stages of sleep
We are just starting to fall asleep and can be easily woken up. (1)
our heart rate starts to slow down and our temperature starts to drop. (2)
We fall into a deeper and deeper sleep.(3+4)
Our eyes move rapidly and our brain is active. (REM)
3 things about basic rest activity cycle (BRAC)
It is an ultradian rhythm of alertness.
cycle lasts 90 minutes.
It helps to explain why professional musicians and athletes break up their practice into short segments.
Tucker et al. didn’t manipulate any independent variables. Instead, they carefully controlled extraneous variables, like the levels of light and the amount of noise.
What type of study is this?
controlled observation
Tucker et al. conducted a controlled observation into people’s stages of sleep.
Tucker et al. found that there were individual differences in the amount of time people spent in each sleep stage.
Tucker et al. found that the biggest individual difference in amount spent in different sleep stages was during deep sleep.
The study showed that ultradian rhythms can vary between different people.
Question 1: Liyana is so tired when she gets home from school that she often falls asleep while watching TV. Most of the time, if someone walks into the room it wakes her up, but sometimes she is so fast asleep that she doesn’t even notice. Explain the stages of the sleep cycle and explain why Liyana only sometimes wakes up.
There are
5
stages to the sleep cycle. The first four stages are called Stage
1
,
Stage
2
,
Stage
3
,
and Stage
4.
The final stage is called rapid eye movement (REM) sleep. Stages
1
and
2
are relatively light stages of sleep, they will be the stages of sleep Liyana is in when she is easily awoken. During stage
2
,
the heart rate and body temperature starts to drop. Stage
3
and Stage
4
are the deepest levels of sleep. This is when Liyana would not be awoken easily and does not notice when someone walks in the room. Finally, REM sleep is a further deep stage of sleep, however this one is characterised by an active brain and rapid eye movements. REM is also the stage most commonly associated with dreaming. We cycle through the
5
sleep stages on average every
90
minutes.
ndividual differences in the sleep cycle are correct?
Tucker et al. found that the largest differences in time spent in a sleep stage were for stages
3
and
4.
Tucker et al. found there were large individual differences in the amount of time people spent in each stage of sleep.
Explain the difference between infradian rhythms and ultradian rhythms. (2 marks)
The difference between infradian and ultradian rhythms is the duration of the rhythms, in that infradian rhythms are more than 24 hours (e.g. the menstrual cycle) whereas ultradian rhythms are less than 24 hours (e.g. stages of sleep).
limitation?? of stages of sleep: individual differences are usually nonbiological factors eg sleep hygiene BUT tucker…
tucker suggests they are biologically determined and may be genetic in origin
ps studied over 11 days and nights, in lab conditions, assessed; sleep duration, time to fall asleep, amount of time in each sleep stage. found large IDs in each characteristics which were consistent across the 8 nights.
IDs were particularly signif for deep sleep stages 3+4
therefore differences between ps were not driven by circumstances but were at least partially bio determined and shows support that ultradian rhythms can vary between people
strength of ult BRAC: research support from ericsson studying violinsts
they studied a group of elite violinists that had practice sessions limited to 90mins, this supports Kleitmans claim that fatigue was a characteristic of the end of the bRAC, ericsson also found that violinists often take naps to recover from practice, the best napping more than their teachers
this was also found for other elites: athletes, chess players, writers
