ultradian and infradian rhythms Flashcards
What are infradian rhythms?
rhythms that take longer than a day/ 24 hours to complete
What are examples of infradian rhythms?
the Menstrual Cycle and Seasonal Affective Disorder (SAD)
What is seasonal affective disorder?
-a depressive disorder with a seasonal pattern of onset
-a circannual infradian rhythm, linked with the prolonged periods of daily darkness in Winter
-high levels of melatonin has a knock-on effect on the production of serotonin
What hormone is thought to be involved in SAD? What does this then effect?
-melatonin, which is thought to reduce levels of serotonin production
What is the menstrual cycle?
-an infradian rhythm that governed by hormone change in the body
-approximately a 28-day cycle, from the first day of a period when the womb lining is shed to the day before her next period
How long does the menstrual cycle last on average?
-28 days
What is an ultradian rhythm?
-rhythms that occur multiple times during a 24-hour period
What is an example of an ultradian rhythm?
-sleep/wake cycle
How long does a full cycle of sleep last (approximately)
90 min
How many sleep stages are there?
5
How is the different brainwave activity of the sleep wake cycle measured?
EEG
What are sleep Stage 1 and 2? What are the characteristics of this stage?
-shallow breathing
-irregular heartbeat
-reduced blood flow
What Brain Waves are detected in sleep stage 1 and 2?
Alpha
How long does Stage 1 last approximately?
15 min
How long does Stage 2 last approximately?
20 min
What are sleep Stage 3 and 4? What are the characteristics of this stage?
-deep sleep/ slow wave sleep
-relaxed muscles, little movement
What Brain Waves are detected in sleep stage 3 and 4?
Delta
How long does Stage 3 last approximately?
15 min
How long does Stage 4 last approximately?
40 min
What is sleep Stage 5? What are the characteristics of this stage?
-REM sleep
-rapid eye movement
-Dreams
-Brain activity closely resembles that of an awake brain
-muscles inactive
What Brain Waves are detected in sleep stage 5?
Theta
How long does Stage 5 last approximately in the first cycle? How long does it last by the 5th cycle?
10 minutes, but by 5th cycle it builds to 1hr.
What are the 3 measures of sleep?
-EEG
-EMG
-EOG
How does an EEG measure sleep?
Measures brain activity through averaging electrical potentials via electrodes on the scalp
How does an EOG measure sleep?
Measures muscle activity of chin
How does an EMG measure sleep?
Measures eye movements- rapid eye movements during dreaming
What are the strengths of infradian and ultradian rhythms?
-development of successful treatments for disorders
-research support that is explained by natural selection
-use of scientific research to support ultradian rhythms
What is the limitation of infradian and ultradian rhythms?
-methodological problems of research into rhythms
Explain the strength of infradian rhythms that there is use of scientific research to support ultradian rhythms?
-One of the benefits of conducting sleep studies in lab settings is the control of extraneous variables.
-This means that a researcher can exclude temporary variables such as noise or temperature that may affect sleep.
-Furthermore, experiments use scientific equipment such as an EEG, which gives empirical data that tells is the sleep stage based off of waves detected in the brain, for example delta waves mean deep sleep.
-However, lab studies involve being attached to complicated machinery, leading participants to sleep in a way that does not represent their ordinary sleep patterns.
Explain the strength of infradian rhythms is the development of successful treatments for disorders?
-One of the most effective treatments for Seasonal Affective Disorder is light therapy, a box which simulates very strong light to reset the boy’s internal clock.
-Studies show this helps reduce the effects of SAD in about 80% of people (Sanassi 2014).
-Light therapy is also preferred over antidepressants to treat SAD because it is regarded as safer.
-However, light therapy can produce headaches and eye strain, and Rohan et al (2009) recorded a relapse rate of 46% over successive winters, compared with a relapse rate of 27% in a group receiving CBT.
Explain the strength of infradian and ultradian rhythms that there research support explained by natural selection.
-Stern & McClintock (1998) found that female menstrual cycles became synchronized with other females through odor exposure.
-Pheromone samples from one group of women were rubbed onto the upper lip of another group.
-Over 2/3 of the women experienced changes to their menstrual cycle which brought them closer to the cycle of their ‘odor donor’.
-This study is thought to have evolutionary value- it may have been advantageous for females to menstruate together and become pregnant at the same time to share resources such as food, thereby improving chances of survival.
Explain the limitation of infradian and ultradian rhythms that there are methodological problems with research support?
-There are many factors that may affect ultradian and infradian rhythms like the sleep stages and menstrual cycle.
-These factors include stress, changes in diet, exercise etc.
-these may act as confounding variables meaning that any supposed pattern of synchronization is no more than would have been expected to occur by chance.
-This may also explain why other studies (e.g, Trevathan et al 1993) have failed to replicate the findings of studies conducted by Stern & McClintock, etc.
