Lesson 11 - Ultradian and Infradian Rhythms Flashcards
What do ultradian rhythms span?
A period of less than 24 hours
What is an example of an ultradian rhythm?
Five sleep stages
What pattern does human sleep follow?
Alternates between REM, stage 5
and NREM, stages 1-4
How often does the human sleep cycle repeat?
Every 90 minutes
What does EEG stand for?
Electroencephalogram
What does a EEG measure?
General activity in the brain
How is an EEG done?
Electrodes are placed on the scalp and measure neuronal activity directly below
What does each sleep stage show?
A distinct EEG pattern
What happens as a person enters deep sleep?
Brainwaves slow and breathing and heart rate decreases
What is the EEG pattern of REM sleep?
It resembles that of an awake person
What happens during REM sleep?
Dreaming
Which sleep stage is REM sleep?
Stage five
What does NREM stand for?
Non-Rapid Eye Movement
What does BRAC stand for?
Basic Rest Activity Cycle
Who talked about BRAC?
Kleitman 1969
What is BRAC?
Name of the 90 minute cycle found during sleep and wakefulness
What did Kleitman suggest about BRAC?
He suggested 90 minute cycle continues when we are awake
What happens to human activity during the day?
We progressively move from a state of alertness to physiological fatigue
What do studies show about the human mind?
We can focus for about 90 minutes
Near the end of the 90 minutes the body begins to run out of resources
Results in loss of concentration, fatigue and hunger
Ericsson et al
2006
Ultradian rhythms
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Studied elite violinists and found group practice sessions were limited to 90 minutes at a time
Violinists frequently napped to recover from practise; the best violinists napping more
Same pattern found among WAC; writers, athletics and chess players
Fits with BRAC
Tucker et al
2007
Ultradian rhythms
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Individual differences in ultradian rhythms which are biologically determined and may be genetic in origin
Participants studied over 11 consecutive days in a lab environment
Sleep duration, time taken to fall asleep and amount of time in each sleep stage was assessed
Differences found in all characteristics
What do infradian rhythms span?
A period of longer than 24 hours
What is an example of an infradian rhythm?
Menstrual cycle
How long does the menstrual cycle last?
Around a month
What did Refinetti 2006 found out about the menstrual cycle?
Variations in the cycle length
Some women experience a 23 day cycle and others a 36 day cycle
What is the average number of days for a menstrual cycle?
28 days
What regulates the menstrual cycle?
Hormones
When does ovulation occur?
Oestrogen levels are at their peak
Roughly halfway through the menstrual cycle
How long does ovulation last?
16-32 hours
What happens AFTER ovulation?
Progesterone levels increase
In preparation for a possible embryo implantation in uterus
Penton-Voak
1999
Infradian rhythms
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Infradian rhythms can affect behaviour
Found women prefer feminised male faces when choosing a partner in long-term relationship
Masculinised faces preferred during ovulation
Pheromones evaluation
Infradian rhythms
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Menstrual cycle is not governed by infradian rhythm alone
No oral contraceptives + several women of childbearing age live together = menstrual cycles synchronise
Samples of sweat collected from one group of women and rubbed onto the upper lip of another group of women; their menstrual cycles synchronised
Suggests pheromones affect synchronisation
What are pheromones?
A chemical substance produced and released into the environment by an animal which affects the behaviour of others of the same species
