Biopsychology Flashcards
Circadian rhythms AO1
24 hour cycles that happen once in a day including physical, mental and behavioural changes. Reset by the levels of light.
Sleep wake cycle is an example of a circadian rhythm. It dictates when animals and humans should be asleep and awake. Daylight(exogenous zeitgeber) makes us feel awake during the day and drowsy during the night. Light is detected by the eyes which then send a message concerning the level of brightness to the SCN.
Core body temperature is another example of a Circadian rhythm. Lowest during the day at 36 degrees during 4am and highest during the evening at 38 degrees during 6pm. Sleep occurs when core temperature starts to drop and body temperate rises towards end of sleep cycle encouraging alertness in the morning.
Circadian rhythms AO3
Supporting research: siffre(1975) found after staying underground with no light or clocks for a while that his 24 hour sleep wake cycle was increased due to a lost perception of time due to absence of external cues which altered his circadian Rythm. Believe the date to be a month earlier.
Aschoff and Wever found after convincing participants to stay in an underground bunker for 4 weeks deprived off natural light, that all but one participant displayed a circadian rhythm between 24 and 25 hours. Both siffre and this study suggest natural sleep cycle may be slightly longer than 24 hours.
Practical application to shift work:
Knowledge or circadian rhythms has given researchers a better understanding of the consequences that occur as a result of their disruption. E.g. night workers engaged in shift work experience reduced concentration at around 6 in the morning meaning mistakes and accidents are more likely(boivin et al 1966)
Practical application to drug treatment:
Research into circadian rhythms has revealed that there are certain peak times during the day or night when drugs are likely to be at their most effective. Lead to development of guidelines to do with timing of drug doses for a whole range of medication(baraldo 2008)
Michael siffre cave study
Research done to investigate circadian rhythms and effect of external cues like light on the systems. Siffre found that absence of external cues significantly altered his circadian rhythm. After staying underground with no light or clocks he lost perception of time by believing it was a month earlier than it was when he had come out. He believed it was august when it was September. Suggests his 24 hour sleep wake cycle was increased by the lack of external cues. Making him believe one day was longer than it was.
AO3
.Study produced a lot of quantitative and qualitative data.
.study was done over a long time allowing siffre to investigate his sleep wake cycle and show how irregular it became.
.only one participant so hard to generalise findings.
.internal validity affected as lights turned on to wake him up and turned off to allow him to sleep could have acted as an external cue.
Infradian rhythms AO1
An example is
Menstrual cycle: governed by hormones roughly on a 28 day basis. Oestrogen levels rise to release an egg from the ovary and progesterone helps the womb lining to grow. If there is no pregnancy then the womb lining sheds.
Seasonal affective disorder: type of depressive disorder which is seasonal. Described as a mental disorder in DSM-5. When there are reduced daylight hours in the winter it can trigger a low mood in the sufferers(circannual rhythm) lack of light causes increased melatonin levels and which creates the low mood. Can also be classed as a circadian rhythm as it’s experience can be due to the disruption of the sleep wake cycle and this can be attributed to prolonged periods of daily darkness during winter.
Infradian rhythms AO3
Penton-volk 1999 study suggests women prefer feminised faces of men in their least fertile stage and more masculine faces in their most fertile stage.
Real word application: sanassi found that a light box can be used to reset melatonin levels and relieve symptoms in up to 80 percent of SAD patients.
Stern and McClintock found that women could synchronise their periods by being exposed to other women’s pheromones. This suggests we should take into account external factors of infradian rhythms.
Ultradian rhythm AO1
More than one cycle in 24 hours(happens more than once in 24 hours)
This cycle alternates between REM (rapid eye movement) and NREM (non-rapid movement) sleep and consists of five stages.
An example of an ultradian rhythm is the sleep cycle:
It has 5 stages which can be identified using an EEG, showing the electrical activity of the brain.
Stage1 and 2: light sleep where you can be easily woken. In stage 1 alpha waves are produced and in stage 2 alpha waves continue but with sleep spindles. (Occasional random changes)
Stages 3 and 4: deep sleep or lower wave sleep. Brain produces lower delta waves Which have a lower frequency and higher amplitude. Difficult to wake someone up in these stages.
Stage 5: REM(rapid eye movement) sleep. The body is paralysed and the activity of the brain resembles someone who is awake. It produces theta waves and the eyes sometimes move around. This is when dreams are most likely to occur.
Ultradian Rythm AO3
Although the method of using EEG to record sleep brain wave activity, it can be invasive and disturb the sleep of participants reducing ecological validity.
Researchers now have an improved understanding of how older people have less slow wave sleep allowing for recommendations of medication and relaxation techniques.
However there are individual difference in each participants stage duration. Tucker et al. Has found large differences between the duration of each stage for different people. Meaning this study cannot be generalised.
Effect of endogenous pacemakers on sleep wake cycle
They are internal mechanisms which determine the biological rhythms for the body e.g. circadian rhythms.
Sometimes referred to as the internal biological clock but can be affected by external environment e.g. light.
SCN is a major factor in sleep wake cycle and is the most important type of endogenous pacemaker.
Specific biological triggers are involved with someone falling asleep:
-eye detects low levels of light.
-then sends this information to SCN
-SCN the. Alerts pineal gland to secrete melatonin.
-melatonin increases which induces sleep.
Effect of endogenous pacemakers AO3
Siffre 1973 cave study demonstrating that humans fall into roughly a 24 hour sleep wake cycle, suggests evidence through its findings that an internal biological clock determines the sleep wake cycle. Supports the effects of endogenous pacemakers.
Reductionist as peripheral oscillators found in other organs have their own Circadian Rhythms suggesting the influence on the sleep wake cycle is more complex than previously thought.
Chipmunk study by decoursey et al suggest through findings that SCN is important. SCN was destroyed in 30 chipmunks and they were returned to the wild. When they returned most were killed by predators not long after as they left nests wrong time of the day.
Effect of exogenous zeitgebers
They are any factors in the sleep wake cycle which act as external cues to either wakefulness or sleepiness. E.g. light and social cues.
.Light can be detected by the eyes but also by the skin influencing secretion of hormones and blood circulation.
.social cues such as mealtime, bedtime, and work schedule can be used to compensate for the lack of light, using these cues instead. They also train babies circadian rhythm to match 24 hours.
Effect of exogenous zeitgebers AO3
Real world application:
Knowledge of E.Z. Can help decrease the impact jet lag has on our sleep wake cycle by providing light and meals at certain times on a plane to match the destinations time zone.
Campbell and Murphy (1988)
Demonstrated that light(Torch) is a key exogenous zeitgeber even when shone on the back of participants knee as it disrupted their sleep cycles by up to 3 hours.
Siffre believed it to be a month earlier than it was when he emerged. Suggest his cycle was increased by the lack of external cues.
Consequence of disruption to biological rhythms
Biological rhythms are regulated by two factors E.Z. And E.P.
E.P. Are internal mechanisms determining biological rhythms of the body.
E.Z. Are any factors in the sleep wake cycle which act as external cues to either wakefulness or sleepiness.
Disturbance/ lack of these factors can result in many consequences for instance:
.shift work related issues where night shift workers experience low concentration around 6 in the morning which can result in accidents and also poor health problems. Happens due to disruption in circadian rhythm and the stress of adjusting to different sleep/wake patterns as well as lack of quality sleep during the day. Shift workers 3 times more likely to develop heart disease.
.jet lag happens due to a disturbance in the exogenous zeitgebers as the patterns of light and social cues such as meal times change.
.Disturbance of SCN(endogenous pacemaker) can result in problems as showcased by decoursey who destroyed the SCN connections in 30 chipmunks and returned them to the wild. Many were killed by predators straight away as they had left their nest at the wrong time of the day.
.siffre case study suggests through results that a lack of exogenous zeitgebers such as daylight caused his biorhythm to settle around 25 hours and cause him to lose perception of time causing him to think it was a month earlier than it was when he emerged.
Consequences of disruption to biological rhythms AO3
Animal studies such as the chipmunk study are unethical as animals cannot give consent to have their SCN removed. The studies are also not generalisable to humans as they are done on animals.
Knowledge of exogenous zeitgebers can help decrease the impact jet lag has on our sleep wake cycle by providing light and meals at certain times on a plane to match the destination time zone.
Shift work related issues can be resolved by keeping workers on their schedule that are based on their sleep wake cycle.
Studies such as siffre which showcase the consequence of disruption to the circadian rhythm can not be generalised as the study was only on siffre himself and people have individual differences.
Plasticity
Brain’s tendency to change and adapt(functionally and physically)
As a result of experience and new learning. Between 2 and 3 years old we have twice as many neural connections as we do as an adult. The synaptic pruning strengthens the connections we use and deletes those we don’t. Our brains are plastic throughout our lives.
Maguire et al study showed this in taxi drivers who had increased grey matter in posterior hippocampus.
Plasticity AO3
Maguire et al study showed a positive correlation in the time spent on the job for london taxi drivers and the amount of grey matter they had. Suggesting brain had changed as a result of the learning taking place.
Draganski et al examined brains of medical students three months before and after final exams there were changes in the posterior hippocampus and parietal cortex.
Support studies such as maguire has good design with the use of a control group allowing us to say there is a significant difference between taxi drivers and other non taxi drivers.
Tang et al. Found that 4 weeks of meditation increases white matter in the anterior cingulate cortex. Which is responsible for self control and regulation.
