Biological Rhythms Flashcards
what are biological rhythms?
an important influence on the way which body systems behave
What are biological rhythms governed by?
- The body’s internal biological ‘clocks’ which are called endogenous pacemakers
- External changes in the environment which are known as exogenous pacemakers
What are the 3 different types of biological pacemakers.
Circadian, ultradian and infradian
What is a circadian rhythm?
A biological rhythm that lasts about 24 hours, which regulates the bodily processes
What are the examples of circadian rhythms?
The sleep-wake cycle and core body temperature
What is the sleep-wake cycle controlled by?
The suprachiasmatic nucleus in the hypothalamus
Which exogenous zeitgerbers are involved with the sleep-wake cycle?
Light and darkness
When does the circadian rhythm dip and why?
2-4am and 1-3pm because that’s when we have our strongest sleep drive
What makes the dip in the circadian rhythms less intense?
If we’ve had enough sleep
What makes the circadian rhythms ‘free-running’?
It will last 24-25 hours with external cues such as light
In what circumstances will the circadian rhythm be disrupted?
Jet lag and night shifts
When is the core body temperature the lowest and highest?
Lowest is 4:30am and highest is 6pm
Why does the core body temperature dip and rise at its specific times?
It dips during sleep and rises during the last hours of sleep to promote the feeling of alertness in the morning
When is there a small drop in the core body temperature and what does this cause?
2pm and 4pm, which causes people to feel sleepy
What is the study supporting circadian rhythms?
Siffre (1975) - spent 6 month in a cave with only artificial light to navigate around the cave. He lost track how long he’d spent in the cave - he thought it was 1 month but it was 6
What are the evaluation points for circadian rhythms?
+ Supporting evidence - Siffre 1975
- Contradictory evidence to Siffre 1975 - Czeizler et al
- Supporting evidence has low population validity
+ Practical application - shift work
What is an infradian rhythm?
A biological rhythm that has a frequency of less than one cycle in 24 hours
What are the examples of an infradian rhythm?
Menstrual cycle and seasonal affective disorder
What is seasonal affective disorder (SAD)?
A depressive disorder that is triggered during the winter months when the number of daylight hours become shorter
What is the study for infradian rhythms -menstrual cycle?
McClintock and Stern (1998)
What was the study of McClintock and Stern 1998?
He got 29 women who had irregular periods, sampled their pheromones and rubbed it on another women upper lip - 68% of women experienced changes to the period cycle
What are the evaluation points for McClintock and Stern 1998?
- Small sample size - 29 women
- Correlational - no cause or effect
- Only 68% of women experienced changes
- Methodological issues
What are the evaluation points for infradian rhythms?
+ Supporting research - McClintock and Stern 1998
+ Practical application - SAD therapy
What is an ultradian rhythm?
A biological rhythms that has a frequency of more than one in 24 hours
What are the examples of ultradian rhythms?
Sleep cycle
What is the sleep cycle?
5 distinct stages of sleep that occur approximately over 90 minutes - each stage is characterised by a different level of brain waves
What are stages 1 and 2 of the sleep cycle?
Light sleep where a person can be easily woken - brain patterns starts to slow down
What are stages 3 and 4 of the sleep cycle?
Deep sleep where it is difficult to wake someone and brain waves are even slower
What is the 5th stage of the sleep cycle?
REM sleep where the body is paralysed yet brain activity speeds up significantly as if the brain is awake -
What does REM stand for?
Rapid eye movement
What is REM?
Fast, jerky activity of the eyes under the eyelids - it’s highly correlated with the experience of dreaming
What is the study for Dement and Kleitman (1957)?
7 males and 2 females were connected to an EEG which took measurements throughout their time asleep
What are the evaluation points for Dement and Kleitman 1957?
- Small sample size - 7 males and 2 females
+ EEG is an objective measure - highly empirical data
What are the evaluation points for ultradian rhythms?
+ Supporting research- Dement and Kleitman 1957
+ Sleep stages are biologically determined
