Biopsychology Flashcards
(17 cards)
Tell me about circadian rhythms
-circadian rhythms are natural internal processes that follow roughly a 24 hour cycle.
-they are controlled the suprachiasmatic nucleus (SCN) in the hypothalamus
-the suprachiasmatic nucleus (an endogenous pacemaker) responds to the levels of light (an exogenous zeitgeber)
the suprachiasmatic nucleus sends signals to control things such as melatonin and body temperature, these both help regulate the sleep wake cycle.
-photoentrainment is the idea that natural light provides input for the suprachiasmatic nucleus, causing the suprachiasmatic nucleus to adjust the body’s natural clock to align with the external light dark cycle
Apply circadian rhythms to the sleep wake cycle
-the sleep wake cycle is an example of a circadian rhythm
-regulated by endogenous pacemakers ( the suprachiasmatic nucleus ) and exogenous zeitgebers ( light )
-light is picked up by receptor cells in the retina and send these signals to the suprachiasmatic nucleus.
-the suprachiasmatic nucleus helps maintain the bodies internal clock and regulates the pineal gland which secretes melatonin. Melatonin is a hormone which induces sleep.
- less light = more melatonin = more sleepy
-more light = less melatonin = less sleepy
Apply circadian rhythms to the body temperature cycle
-the body temperature cycle is another example of a circadian rhythm
-this rhythm is also controlled by the SEN
-body temperature is lowest ( around 36C ) in the early morning ( 4-5 am )
-then throughout the day the body temperature rises peaking ( 38C ) in the late afternoon/ early evening ( around 6pm ).
-this rise in temperature promotes alertness
-cognitive performance tends to be best when body temperature is the highest.
-fall in temperature triggers feelings of sleepiness
Siffre’s study
Siffre spent long periods of time in caves with no exogenous zeitgeibers like light or clocks.
In one study he spent about 2 months in a cave in the Alps. During this time he followed his bodies natural rhythms- waking, eating and sand sleeping when he felt like it. He felt as if he spent a shorter amount of time compared to how much he actually did. In another study, he stayed 6 months in a Texan cave. His circadian rhythm settled to around 25 hours showing that the sleep wake cycle is controlled by an internal clock. Both of his cave stays show us the importance of exogenous zeitgeibers in synchronising out circadian rhythms to the 24 hours showing day
Circadian rhythms AO3 (STRENGTHS)
+ One strength of circadian rhythms is the real world application
We can take it into account in the field of chronotherapeutics (the study of how timing affects drug treatments) for example asthma symptoms worsen at night due to the circadian rhythm of lung function, the airways of the lungs tend to become narrower at night making it harder to breathe, so taking an inhaler before you sleep can help prevent symptoms developing while you sleep.
+another practical application of cardiac rhythms is knowing the negative circadian disruption, especially in shift work. Working night shifts causes desynchronisation between the internal body clock and external environment which can impair functioning, understanding this has practical value, as employers can adjust work schedules if possible to ensure that critical tasks are not scheduled during periods of low alertness.
+ Knutsson (2003) found that individuals who work night shifts are three times more likely to develop heart disease compared to those who work regular daytime hours. This supports the idea that chronic disruption of circadian rhythms can have harmful effects on physical health, highlighting the importance of designing work schedules that align more closely with natural biological rhythms.
Circadian rhythms AO3 (WEAKNESSES)
-one weakness of research into circadian rhythms ( like siffres ) is that artificial light was used in the study, initially researchers believed this had minimal effects on our circadian rhythms however Czeisler et al found out that artificial light can influence circadian rhythms shifting them between 22-28hrs depending on brightness and timing , suggesting there is confounding variables such as artificial light decreasing the internal validity of early research into circadian rhythms.
-only 1 participant in siffres study
Infraradian rhythms AO1
Infraradian rhythms are biological cycles which last more than 24 hours
EXAMPLE 1: THE MENSTRUAL CYCLE
this lasts 28 days
stage 1: menstruation occurs the uterus lining sheds
stage 2: oesteragon helps cause the build up of the lining of the uterus again, also stimulates LH
stage 3: LH triggers the release of an egg
stage 4: the lining of the ovary is maintained by progesterone in case of pregnancy , if no pregnancy the cycle restarts
EXAMPLE 2: SAD- SEASONAL AFFECTIVE DISORDER
research has shown that seasonal variation can affect mood and this is seen in seasonal affective disorder
SAD follows a yearly cycle
SAD occurs during the autumn and winter months
lack of light during these months increase melatonin secretion which affects serotonin secretion which causes depressive symptoms
Dement and Kleitman
-aimed to investigate brain activity change throughout night time sleep
-participants were asked to report to the laboratory at bedtime where they were connected to an EEG
-EEG took measurements throughout their sleep
-participants asked to not drink caffine the days their sleep was investigated
-during the night participants were woken up at different stages of sleep by the sound of a bell
-once awake they would then report if they were dreaming and gave details of their dream
-found that all participants had periods of REM sleep evey night and found high insidences of dream recall when participants were awoken from REM sleep, when awoken in nREM stages there were little reports of dreaming
-concluded that stages of sleep follow cycle between nREM and REM sleep and dreams occur in REM sleep
Ultradian rhythms AO1
-biological cycles that last less than 24 hours
-for example the sleep wake cycle which lasts 90 minutes
-goes through 5 stages
-in stage 1 light sleep our brain waves go from alpha to theta waves, slowing down. in stage 2 light sleep our brain waves are still theta waves but now with k complexes and sleep spindles (said to help memory consolifation and protecting sleep)
-stage 3 and 4 involve deep sleep and the theta waves go to delta waves, its really hard to wake up here
-stage 5 is REM sleep , brain waves are simillar to that awake- beta waves
infraradian rhythms ao3
+One strength of research into infraradian rhythms is that there is supporting research, McClintock and Stern found that womens menstural cycles could be influences by phermones. In their study women were given samples of phermones from the armpits of women in the study to inhale from donore. 68% of the participants found that their menstural cycle synched with their pad donor. Showing that infraradian rhythms can be influenced by exogenous zeitgebers and endogenous pacemakers.
+This was a longatudinal study, changes over time could be tracked. increasing validity of findings
-procedure raises hygine concerns, applying other peoples sweat to upper lip. no illnesses reported but could make participants less willing to commit to the study. told to not wipe sweat off for 6 hours to ensure adequate exposure to compounds, some people may have wipes it off early due to the unpleasant nature of the task impacting the internal validity of the study.
+Reinberg also supports the idea that the menstural cycle is governed by exogenous zeitgebers, he examined a woman who spent 3 months in a cave with only dim light. Reinberg noticed that her mentural cycle decreased to 25.7 days from 28. Showing a lack of light can affect a mensural cycle, demonstrating the effect of external factors on infradian rhythms.
+serotonin and melatonin imbalances have been found in people with SAD during the winter months showing that it is something biologically driven and closely tied to our bodies natural rhythm
+understanding infraradian rhythms can help provide treatments, one is phototherapu, which has been shown by eastman improved symptoms in 60% of sufferers
-but this may be a placebo effect 30% symptoms improved with a placebo negative ion generator showing that phototherapy may be due to part placebo effect.
ultraradian rhythms ao3
+dement and kleitman research support for stages of sleep
+another strenght is that it is useful in prsctical applications, for example in improving sleep quality. knowing that sleep cycles follow approximately 90 minutes has lead to avice suggesting we should sleep in multiples of 90 minuyes eg 6 or 7.5hours to wake up at the end of the sleep cycle where we are in light sleep, as waking up in a lighter sleep helps us feel more refreshed and alert compared to waking u[p in deep sleep wich makes us feel groggy. increasing ecological validity
-One limitation of research into ultradian rhythms is that there is individual differences. Tucker et al found large differences between participants duration of each sleep stage showing that ultraradian rhythms are not fixed or universal and depend on a variety of factos such as age lifestyle stress etc, so it may be difficult to generalise the findings of ultradian rhythms to everyone reducing external validity.
endogenous pacemakers AO1
internal biological clocks within the body which govern and regulate biological processes
most important one is the suprachiasmatic nucleus in the hypothalamus, regulates circadian rhythms like sleep wake cycle
SCN acts as a master clock and also recieves information about light via the optic nerve and adjusts the internal clock accordingly, esp in response to morning and night, despite having an inbuilt circadian rhythm it still does need resetting
SCN controls pineal gland which is responsible for melatonin secretion
without SCN circadian rhythms would become disrupted
endogenous pacemakers ao3
+There is strong evidence to support the idea that the SCN is an endogenous pacemaker. Morgan bred hamsters with abnormal circadian rhythms of 20 hrs and transplanted their SCN neurons into normal hamsters. The recipitent hamsters also adopted the 20 hrs circadian rhythms, demonstrating th important role the SCN plays in maintaining the internal body clock, as altering it directly changed the circadian rhythm
+Additional research has shown the importance of the SCN in natural environments. DeCoursey et al destroyed the SCN in chipmunks and returned them to the wild. Their sleep wake cycles were disrupted and many were killed by predators. This shows without a functioning SCN animals are unable to regulate their sleep patterns properly which can have serious survival consequences.
+In one of Siffres studies, he stayed 6 months in a Texan cave. His circadian rhythm settled to around 25 hours showing that the sleep wake cycle is still controlled by an internal clock.
-THE ANIMAL STUDIES WERE HELLA UNETHICAL BRO WHAT INVASIVE PROCEDURES ON ANIMALS AND HELLO ANIMAL STUDIES CANT REALLY EB GENERALISED TO HUMANS
exogenous zeitgebers ao1
exogenous zeitgebers are external environmental cues that help rehulate the bodies biological rhythms eg light and social routines
LIGHT is the most significant exogenous zeitgeber, detected by melapsonin containing cells in the retina, sending signals to the SCN to reset the biological clock daily
when the light dark circle changed such as during jet lag or shift work the mismatch between the internal rhythms and external light cues can lead to anxiety, fatigue and disrupted sleep.
SOCIAL CUES such as mealtimes and bedtimes also act as zeitgebers. Aschoff et al showed that people could maintain sleep wake cycles based on these cues even without natural light
exogenous zeitgebers ao3
+One strength of understanding exogenous zeitgebers is that they have practical value. In infants , initially the sleep wake cycle is random but parents imposing mealtimes and bedtimes can help them form a sleep/wake cycle. This shows the real world application as it is not only scientifically valuable bit it can benefit families.
+Another practical value is shown in Burgess et als study which shows that exposure to bright light before an east west flight helped travellers adjust more quickly to new time zones. Showing how exogenous zeitgebers can reset circadian rhythms
+In one of Siffres studies, he stayed 6 months in a Texan cave. His circadian rhythm settled to around 25 hours showing that the sleep wake cycle is controlled by an internal clock but also impacted by exogenous zeitgebers as he had no natural light in his stay in the cave. His cave stays show us the importance of exogenous zeitgeibers in synchronising our internal clock
-However not all studies support the uniform influence of light on the sleep wake cycle. Vetter et al found that participants exposed to warm lights synced with dawn while those exposed to blue lights synced with office hour, showing that not only the presence of light, but the temperature can affect circadian rhythms, Showing us that different types of light affect our circadian rhythms differently so its important to be careful of generalising the studies of light affecting circadian rhythms
Plasticity of the brain
Plasticity refers to the ability of the brain to change and adapt synapses pathways and structures in light of various experiences
Experiences can be positive eg learning or negative eg brain trauma
Placticity in a new born brain: By the end of a first years of a babys life, the brain actually has more neurones and more synapses than it will have when it becomes fully mature in late adolescense/ early childhood. It’s a good time to study plasticity of the brain. The reason why there are so more neurones and synapse because the developing brain is exposed to a vast range of experiences and thus alot of learning has to be done.
Villablanca and Hovda found removing a severely damaged hemisphere soon after birth prevents the individual from suffering from behavioural/cognitive impairments
= the brain can adapt to the loss of a hemisphere quickly due to maximal plasticity and can reallocate functions
BRAIN PLASTICITY THROUGH EXPERIENCES
As people gain new experiences, nerve pathways that are used frequently develop stronger connections, while unused ones are removed through synaptic pruning. Hebb (1949) explained this by saying “neurons that fire together wire together,” meaning the brain adapts by strengthening active pathways. Boyke et al. (2008) found that 60-year-olds who learned to juggle showed increased grey matter in the visual cortex, but these changes reversed when they stopped, suggesting plasticity continues with age but may be temporary.
