biological rhythms: circadian rhythms Flashcards
what is a biological rhythm?
it is a change in the body processes or behaviour in response to cyclical changes within the environment. They are influenced by internal body clocks and external changes to the environment.
what is our biological clock?
they are organisms natural timing devices regulating the cycle of circadian rhythms. They are composed of specific molecules that interact with cells throughout the body and nearly every tissue or organism contains biological clocks.
what is a circadian rhythm?
they are physical, mental and behavioural changes that follow a 24 hour cycle. These natural processes respond primarily to dark and light and affect most living things. Chronobiology is the study of sleep cycles.
what is an example of a circadian rhythm?
One type of light-related circadian rhythm is our sleep cycle. This means that our body knows that when it is daytime we are awake, and at night we are asleep.
what is the master clock?
this is the part of the brain that coordinates all the biological clocks in a living thing, keeping the clocks in sync. In humans and vertebrate animals, the master clock is a structure called the SCN. This is part of the hypothalamus and it receives direct input from the eyes.
how does the master clock regulate our sleep cycle?
The master clock helps to regulate our sleep cycle as the period and cryptochrome genes code for proteins that build up in the cells nucleus at night and lessen during the day. Studies into fruit fly’s suggested that these proteins help activate feelings of wakefulness, alertness and sleepiness. However, signals from the environment also effect circadian rhythms such as exposure to light at different times of the day can impact when the body turns on period and cryptochrome genes.
what are the other bodily influences on our sleep cycle?
Circadian rhythms influence important functions such as hormone release, eating habits and digestion and our body temperature. However the most noticeable effect is on our sleep patterns as the SCN controls the production of melatonin which is the hormone that effects our sleep levels. The SCN receives information about incoming light from the optic nerves which relay information from the eyes to the brain, so if they detect less light, the SCN notifies the brain to produce more melatonin causing drowsiness.
what other factors effect our circadian rhythms and what can they cause?
Some factors that effect our circadian rhythms are mutations or changes in certain genes which effect our biological clocks, jet lag or shift work which causes changes in the light-dark schedule, light from electronic devices at night. These changes can cause sleep disorders, obesity, diabetes, depression, bipolar.
how does jet lag effect our circadian rhythm?
Jet lag can effect circadian rhythms as when you travel through different time zones, your biological clock will be different to the local one. Your biological clock will reset but it will happen at a different rate and it often takes a few days for your biological clock to align with a new time zone. Adjusting after ‘gaining’ time may be slightly easier than after ‘losing’ time because the brain adjusts differently in the two situations.
how do researchers investigate circadian rhythms?
Researchers look into circadian rhythms by studying humans and using organisms with similar biological clock genes such as fruit flies and mice. Researchers do these experiments by controlling the subjects environment by altering the light and dark periods. They then look for differences in gene activity and other molecular signals. Scientists may also study organisms with irregular circadian rhythms to identify which genetic components of biological clocks may be broken.
AO3: how is ‘real life application’ a strength to research into circadian rhythms?
One strength to research into circadian rhythms is that it has good real life application. This is because research into circadian rhythms has highlighted the negative consequences that can occur as a result of desynchronisation. This means that we are able to improve the way people adjust for nighttime work so that the effects on their biological clock and circadian rhythms are minimal. For example, shift workers experienced a reduced concentration at about 6am as a result of a circadian through leading to more mistakes being mace and accidents are likely, meaning this is usually time in which shift changes happen to avoid mistakes due to tiredness. Therefore, understanding circadian rhythms has real health and economic implications in terms of how to manage worker productivity such as when to take breaks.
AO3: how is ‘individual differences’ a limitation of research into circadian rhythms?
one limitation to research into circadian rhythms is that it doesn’t account for individual differences. This is because we know that there are individual differences within circadian rhythms as some individuals are morning people whereas others are evening people. Other research has also suggested that there are age differences within the sleep/wake patterns with younger people having a different circadian rhythm compared to older people as teenagers tend to be up later and sleep longer compared to someone who is older as they tend to sleep less but earlier. Therefore, this suggests we can only generalise the findings to a certain extent as it doesn’t account for certain differences.
AO3: how is ‘lacks generalisability’ a limitation of research into circadian rhythms?
one limitation to research into circadian rhythms is that it lacks generalisability. This is because both Siffre and Aschoff & Wevers research involved either a single participant or a very small number of participants. We know that Siffre conducted his research on himself and he spend long periods of time in isolation which could’ve impacted his circadian rhythm. Therefore, this means that the extent to which we can generalise to the wider population that is meaningful is limited.
AO3: how is ‘drug treatments’ a strength to research into circadian rhythms?
one strength to research into circadian rhythms is that they have helped us to develop the optimum times to take certain drugs. This is because circadian rhythms co-ordinate the bodies basic processes such as the heart rate, digestion and our hormone levels. These basic processes effect pharmacokinetics, this is the action of drugs on the body including how well they are absorbed and distributed. Therefore, by understanding our circadian rhythms, a large range of guidelines have been developed about when to take drugs, the dosage of the drug and the gap you should leave when taking the drug between doing other things.
AO3: how is ‘supporting evidence’ a strength to circadian rhythms as a biological rhythm?
one strength to circadian rhythms as a biological rhythm is that it has supporting evidence. For example, Siffre’s cave study where he spend hours underground measuring his own biological rhythms. He did this by depriving himself of natural light and sound in the caves of the southern alps where he then resurfaced 2 months later in mid-September. He found that everytime he went into the caves his biological rhythm settled into a regular 25 hour cycle and he continued to wake up and fall asleep on a regular basis. Therefore, this supports the idea that even with no natural light, our body settles itself into a regular 25 hour cycle, suggesting there is a biological component to our bodys rhythms.
