biological rhythms
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1
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what are circadian rhythms?
* A type of biological rhythm that operates along a 24/25 hour cycle.
* This regulates a number of bodily processes such as the sleep/wake cycle and core body temperature.
* This regulates a number of bodily processes such as the sleep/wake cycle and core body temperature.
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where is the circadian rhythms located?
* in the suprachiasmatic nucleus (SCN) in the hypothalamus of the brain, one in each brain hemisphere
* patterns of light and darkness are registered by the retina, travel up the optic nerves to where these nerves join (optic chiasma), and then pass into the SCN.
* if this nerve connection is severed circadian rhythms become random.
* the same effect is produced by damaging the SCN of rats, and people born without eyes cannot regulate bodily rhythms.
* patterns of light and darkness are registered by the retina, travel up the optic nerves to where these nerves join (optic chiasma), and then pass into the SCN.
* if this nerve connection is severed circadian rhythms become random.
* the same effect is produced by damaging the SCN of rats, and people born without eyes cannot regulate bodily rhythms.
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how does melatonin affect the sleep/wake cycle?
* When our brain registers darkness it produces melatonin that makes us sleepy. When our brain detects light we stop producing melatonin and eventually wake up. This is why in a dark room when it is warm we feel sleepy, whereas we find it hard to sleep in bright areas.
* The homeostatic drive for sleep increases gradually throughout the day, as we use up energy in activity.
* The most important hormones affected by the circadian clock for sleep are:
* Melatonin (which is produced in the pineal gland in the brain - causes drowsiness and lowers body temperature)
* Cortisol (produced in the adrenal gland, and used to form glucose or blood sugar. Also controls stress)
* The homeostatic drive for sleep increases gradually throughout the day, as we use up energy in activity.
* The most important hormones affected by the circadian clock for sleep are:
* Melatonin (which is produced in the pineal gland in the brain - causes drowsiness and lowers body temperature)
* Cortisol (produced in the adrenal gland, and used to form glucose or blood sugar. Also controls stress)
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ao3 + evidence of a ‘free running’ circadian rhythm?
* Michel Siffre spent six months in a cave in Texas with no daylight, clocks or radio, and his circadian rhythm settled to just over 24 hours, but with some dramatic variations (days were out of sync)
* When he stayed underground at age 60, his circadian rhythm had slowed down, sometimes stretching to 48 hours.
* This shows that the circadian rhythm is not wholly dependent on light or social cues and can vary with age.
* When he stayed underground at age 60, his circadian rhythm had slowed down, sometimes stretching to 48 hours.
* This shows that the circadian rhythm is not wholly dependent on light or social cues and can vary with age.
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ao3 + there are individual differences in circadian rhythms?
* One is the cycle length; research has found that circadian cycles can vary from 13 to 65 hours.
* The other type of individual difference relates to cycle onset - individuals appear to be innately different in terms of when their circadian rhythms reach their peak.
* This would explain why some people prefer to rise early and go to bed early (about 6 am and 10 pm), whereas others prefer to wake and go to bed later (10 am and 1 am).
* The other type of individual difference relates to cycle onset - individuals appear to be innately different in terms of when their circadian rhythms reach their peak.
* This would explain why some people prefer to rise early and go to bed early (about 6 am and 10 pm), whereas others prefer to wake and go to bed later (10 am and 1 am).
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ao3 - methodological flaws in early research studies?
* In most studies, participants were isolated from variables that might affect their circadian rhythms, such as clocks, radios and daylight.
* However, they were not isolated from artificial light because it was believed that dim artificial light, in contrast to daylight, would not affect their circadian rhythms.
* Czeisler et al. (1999) altered participants' circadian rhythms down to 22 hours and up to 28 hours by using dim artificial lighting alone. This weakens the evidence of earlier studies.
* However, they were not isolated from artificial light because it was believed that dim artificial light, in contrast to daylight, would not affect their circadian rhythms.
* Czeisler et al. (1999) altered participants' circadian rhythms down to 22 hours and up to 28 hours by using dim artificial lighting alone. This weakens the evidence of earlier studies.
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ao3 - temperature may be more important than light in setting the body clock?
* It seems that the SCN transforms information about light levels into neural messages that set the body's temperature.
* Buhret al. found that fluctuations in body temperature over the 24-hour period cause tissues to become active or inactive.
* So, although the SCN responds to light, the circadian fluctuation of body temperature may actually control the other biological rhythms.
* Buhret al. found that fluctuations in body temperature over the 24-hour period cause tissues to become active or inactive.
* So, although the SCN responds to light, the circadian fluctuation of body temperature may actually control the other biological rhythms.
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what are infradian rhythms?
* A type of biological rhythm that operate less than once a day
* This regulates a number of bodily processes such as the menstrual cycle (24-35 days) and SAD (over a year)
* This regulates a number of bodily processes such as the menstrual cycle (24-35 days) and SAD (over a year)
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how does the menstrual cycle work?
* the menstrual cycle is usually around 23-35 days long
* ovulation usually occurs around 12 to 16 days before your period starts
* this peak in estrogen triggers a brief surge in Luteinizing Hormone (LH), which triggers ovulation within usually 24 hours
* progesterone helps to prepare the body for pregnancy by stimulating glandular development and the development of new blood vessels
* ovulation usually occurs around 12 to 16 days before your period starts
* this peak in estrogen triggers a brief surge in Luteinizing Hormone (LH), which triggers ovulation within usually 24 hours
* progesterone helps to prepare the body for pregnancy by stimulating glandular development and the development of new blood vessels
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what was McClintock’s study on the exogenous influences of the menstrual cycle?
* studied 29 women with a history of irregular periods
* Samples of Pheromones were gathered from 9 of the women at different stages of their menstrual cycle for were they, see above), via a cotton placed under their armpit.
* the pads were worn at least 8 hours to ensure that pheromones were picked up.
* the pads were treated with alcohol and frozen, to be rubbed on the upper lip of the other participants.
* on day one, pads from the start of the menstrual cycle were applied to all 20 women, on day two they were all given a pad from day two, and so on.
* Mclintock found that 68% of women experienced changes to their cycle which brought them closer to the cycle of their odour donor.
* This indicates that the menstrual cycle is influenced by exogenous factors (the presence of other women- via pheromones).
* Samples of Pheromones were gathered from 9 of the women at different stages of their menstrual cycle for were they, see above), via a cotton placed under their armpit.
* the pads were worn at least 8 hours to ensure that pheromones were picked up.
* the pads were treated with alcohol and frozen, to be rubbed on the upper lip of the other participants.
* on day one, pads from the start of the menstrual cycle were applied to all 20 women, on day two they were all given a pad from day two, and so on.
* Mclintock found that 68% of women experienced changes to their cycle which brought them closer to the cycle of their odour donor.
* This indicates that the menstrual cycle is influenced by exogenous factors (the presence of other women- via pheromones).
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how do annual rhythms work?
* annually rhythms are related to seasons.
* For example in animals migration occurs in response to lower body temperatures.
* this also may affect human behaviour, as research suggests seasonal variations in mood in particular for women, with some people becoming severely depressed in the winter months.
* For example in animals migration occurs in response to lower body temperatures.
* this also may affect human behaviour, as research suggests seasonal variations in mood in particular for women, with some people becoming severely depressed in the winter months.
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how does SAD work?
* sometimes referred to as a circadian rhythm
* melatonin is secreted for a longer period of time due to lack of light
* this is thought to have an effect on the neurotransmitter serotonin, creating depressive symptoms
* the winter is also associated with an increase in heart attacks and there is a robust annual rhythm in human deaths with most people during in January
* melatonin is secreted for a longer period of time due to lack of light
* this is thought to have an effect on the neurotransmitter serotonin, creating depressive symptoms
* the winter is also associated with an increase in heart attacks and there is a robust annual rhythm in human deaths with most people during in January
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what was Eastman’s SAD bulb study?
* lack of sunlight creates depression in some people, phototherapy has been found to be an effective treatment.
* Eastman randomly assigned 96 patients with winter SAD to one of three bright-light treatments that are about 10 to 20 times brighter than ordinary indoor lights.
* patients either got an hour and a half of bright light in the morning, an hour and a half the evening, or a morning placebo of two deactivated negative-ion generators
* after three weeks, 60% more of the morning light group than in the placebo group showed more complete or near complete remission of their symptoms
* the response to evening light was also better than the placebo but not at a level of significance
* 30% of the sufferers in the placebo group also recovered
* Eastman randomly assigned 96 patients with winter SAD to one of three bright-light treatments that are about 10 to 20 times brighter than ordinary indoor lights.
* patients either got an hour and a half of bright light in the morning, an hour and a half the evening, or a morning placebo of two deactivated negative-ion generators
* after three weeks, 60% more of the morning light group than in the placebo group showed more complete or near complete remission of their symptoms
* the response to evening light was also better than the placebo but not at a level of significance
* 30% of the sufferers in the placebo group also recovered
14
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ao3 + further research into the role of pheromones in the control of the infradian rhythms of mentryation
* further research has supported the role of pheromones (EZs) along with EPs in the control of the infradian rhythm of menstruation.
* for example, Sabbagh and Barnard (1984) found that women who spend a lot of time together often find their menstrual periods become synchronised. It is suggested that this is due to the unconscious detection of chemical scents (pheromones) secreted at certain times during the menstrual cycle.
* this is a strength because it further supports the idea that infradian rhythms such as the menstrual cycle are controlled mainly by internal biological processes (EPs) but, can be modified by external factors (EZs, for example, pheromones).
* for example, Sabbagh and Barnard (1984) found that women who spend a lot of time together often find their menstrual periods become synchronised. It is suggested that this is due to the unconscious detection of chemical scents (pheromones) secreted at certain times during the menstrual cycle.
* this is a strength because it further supports the idea that infradian rhythms such as the menstrual cycle are controlled mainly by internal biological processes (EPs) but, can be modified by external factors (EZs, for example, pheromones).
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ao3 - ethical issues with McClintock?
* due to the fact that research into this area tampers with the infradian rhythm of menstruation, research can be criticised as being unethical.
* research from McClintock have purposely changed the length of its female participant menstrual cycles.
* *t*his is a weakness because researchers are not fully aware of the implications of modifying/tampering with such cycles. Such changes could negatively affect female biological processes which is a lack of protection of participants.
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* research from McClintock have purposely changed the length of its female participant menstrual cycles.
* *t*his is a weakness because researchers are not fully aware of the implications of modifying/tampering with such cycles. Such changes could negatively affect female biological processes which is a lack of protection of participants.
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ao3 - field experiments
* In addition, much of the research is based on field experimental methods and therefore the is a lack of control over extraneous variables
* *f*or example, researchers such as McClintock are unable to control other external factors that could affect the female menstrual cycle (e.g. stress, exercise/physical activity etc ).
* this is a weakness because the lack of control over such variables makes it difficult for researchers to confirm ca cause and effect relationship between the presence of pheromones and the lengthening/shortening of the female menstrual cycle.
* *f*or example, researchers such as McClintock are unable to control other external factors that could affect the female menstrual cycle (e.g. stress, exercise/physical activity etc ).
* this is a weakness because the lack of control over such variables makes it difficult for researchers to confirm ca cause and effect relationship between the presence of pheromones and the lengthening/shortening of the female menstrual cycle.
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what is an ultradian rhythm?
* a type of biological rhythm that operates more than once a day
* this regulates a number of bodily processes such as the sleep cycle
* this regulates a number of bodily processes such as the sleep cycle
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what is the brain like when awake?
* high frequency
* low amplitude
* conscious thought
* alpha waves + beta waves
* >12 Hz
* low amplitude
* conscious thought
* alpha waves + beta waves
* >12 Hz
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NREM 1?
* transition state between sleep and wakefulness
* this stage only lasts a few minutes
* increased amplitude
* lower frequency than being awake
* alpha waves + theta waves
* theta waves: 4-8Hz
* hypnogogic hallucinations - hallucinations that happen as you're falling asleep
* hypnic jerks - sudden, involuntary muscle contractions you may experience as you are falling asleep
* tetris effect - occurs when people devote so much time and attention to an activity that it begins to pattern their thoughts, mental images, and dreams
* this stage only lasts a few minutes
* increased amplitude
* lower frequency than being awake
* alpha waves + theta waves
* theta waves: 4-8Hz
* hypnogogic hallucinations - hallucinations that happen as you're falling asleep
* hypnic jerks - sudden, involuntary muscle contractions you may experience as you are falling asleep
* tetris effect - occurs when people devote so much time and attention to an activity that it begins to pattern their thoughts, mental images, and dreams
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NREM 2?
* increased amplitude
* lower frequency than stage 1
* K complexes (biggest amplitude wave observed in the brain)
* sleeps spindles (burst of very rapid brain activity)
* these are linked to brain processes which help to ‘damp down’ external stimuli and keep us asleep
* K complexes are also linked to the memory consolidation which occurs during sleep
* theta waves + sleep spindles and K-complexes
* 8-15 Hz
* lower frequency than stage 1
* K complexes (biggest amplitude wave observed in the brain)
* sleeps spindles (burst of very rapid brain activity)
* these are linked to brain processes which help to ‘damp down’ external stimuli and keep us asleep
* K complexes are also linked to the memory consolidation which occurs during sleep
* theta waves + sleep spindles and K-complexes
* 8-15 Hz
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NREM 3?
* increased amplitude
* lower frequency than stage 2
* deep sleep - very slow brain waves
* dreaming more common than in other NREM stages, but any dreams in this stage are more disorganised and less easily remembered than in REM sleep
* 20-50% Delta + Theta waves
* 2-4Hz
* delta waves have lower frequency, greater amplitude than theta
* parasomnias - dreams
* lower frequency than stage 2
* deep sleep - very slow brain waves
* dreaming more common than in other NREM stages, but any dreams in this stage are more disorganised and less easily remembered than in REM sleep
* 20-50% Delta + Theta waves
* 2-4Hz
* delta waves have lower frequency, greater amplitude than theta
* parasomnias - dreams
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REM?
* paradoxical sleep - similar brain wave pattern to the waking state
* beta waves indicate activity in the brains visual cortex
* muscles are relaxed, except for occasional twitches
* heart may beat faster, and breathing becomes shallow and rapid
* most vivid dreaming occurs during this stage
* >12 Hz
* beta waves indicate activity in the brains visual cortex
* muscles are relaxed, except for occasional twitches
* heart may beat faster, and breathing becomes shallow and rapid
* most vivid dreaming occurs during this stage
* >12 Hz
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how long is the sleep cycle
90 minute cycles
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ao3 + lab experiments
* the research into ultradian rhythms can be praised for being conducted in controlled laboratory settings.
* for example, research looking at the stages of sleep uses EEG and ERP mechanisms (to name a few) to measure the waves occurring in the brain.
* this is a strength because, research from Dement and Kleitman and Rechtschaffen and Kales can be seen to produce scientific and objective measures that allow research to draw firm conclusions about the specific characteristics associated with the different stages of sleep (e.g. brain activity, muscle acidity, eye activity) which increased internal validity.
* for example, research looking at the stages of sleep uses EEG and ERP mechanisms (to name a few) to measure the waves occurring in the brain.
* this is a strength because, research from Dement and Kleitman and Rechtschaffen and Kales can be seen to produce scientific and objective measures that allow research to draw firm conclusions about the specific characteristics associated with the different stages of sleep (e.g. brain activity, muscle acidity, eye activity) which increased internal validity.
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ao3 - lab experiments
* due to the fact that research is conducted in the control setting of a laboratory, the sleep environment can be criticised for its artificial nature.
* for example, sleep research involves individuals sleeping under circumstances that don’t usually reflect their ‘typical’ nights sleep. Participants sleep with electrodes attached to their body/head, are often woken up a numbers of times throughout the night in order to report dreams etc Furthermore, they are sleeping in a lab setting not their usual bedroom setting.
* this is a weakness because the research can be criticised for lacking ecological validity and not reflecting an individuals true sleep behaviour.
* for example, sleep research involves individuals sleeping under circumstances that don’t usually reflect their ‘typical’ nights sleep. Participants sleep with electrodes attached to their body/head, are often woken up a numbers of times throughout the night in order to report dreams etc Furthermore, they are sleeping in a lab setting not their usual bedroom setting.
* this is a weakness because the research can be criticised for lacking ecological validity and not reflecting an individuals true sleep behaviour.
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ao3 - androcentric
* due to the fact that research is conducted in the control setting of a laboratory, the sleep environment can be criticised for its artificial nature.
* for example, sleep research involves individuals sleeping under circumstances that don’t usually reflect their ‘typical’ nights sleep. Participants sleep with electrodes attached to their body/head, are often woken up a numbers of times throughout the night in order to report dreams etc Furthermore, they are sleeping in a lab setting not their usual bedroom setting.
* this is a weakness because the research can be criticised for lacking ecological validity and not reflecting an individuals true sleep behaviour.
* for example, sleep research involves individuals sleeping under circumstances that don’t usually reflect their ‘typical’ nights sleep. Participants sleep with electrodes attached to their body/head, are often woken up a numbers of times throughout the night in order to report dreams etc Furthermore, they are sleeping in a lab setting not their usual bedroom setting.
* this is a weakness because the research can be criticised for lacking ecological validity and not reflecting an individuals true sleep behaviour.