Biological rhythms Flashcards
What are the biological rhythms?
Circadian, infradian and ultradian rhythms.
What are biological rhythms?
Patterns of changes in body activity that conform to cyclical (recurrent) time periods.
These are influenced by internal body clocks (endogenous pacemakers) and external changes to the environment (exogenous zeitgebers)
What’s the sleep/wake cycle?
Average length – 24/25 hours
The fact that we feel drowsy when it’s nighttime and alert during the day demonstrates the effect of daylight – an important exogenous zietgeber – on our sleep/wake cycle.
What are circadian rhythms?
Type of biological rhythm which is based on a 24-hour cycle which regulates several body processes. (i.e. these rhythms last for around 24 hours a day)
Examples- sleep/wake cycle and core body temperature changes.
What is core body temperature?
Core body temperature varies by around two degrees centigrade
during the course of a day. It is at its lowest around 4 in the morning (36°C) and peaks around 6 in the evening at 38°C.
Evidence suggests that body temperature may have an effect on our mental abilities: the warmer we are (internally), the better our cognitive performance.
What did Michael Siffre do and find?
Michel Siffre in (1975), spent 6 months underground in a cave in Texas, in dim light; he had no cues as to the time of day. He had food, water, exercise equipment and books. He had a telephone link to the outside world which was staffed all the time. Siffre was wired up via computer and video so that his bodily functions could be monitored all the time.
Findings: Siffre’s bodily rhythms were erratic at first (he went into a state of internal desynchronisation), but they soon settled down into regular cycles of activity/inactivity e.g., sleep/wake, eating, etc. An interesting finding was that the daily cycle that he established seemed to run to 25 hours (approx.’) and not 24 hours. However, sometimes his cycle would change dramatically and run over 48 hours. This meant that when he emerged from his period of isolation, he had “lost” a considerable number of days, it was the 179th day, whereas by his “days” it was only the 151st. He therefore LOST 28 days!
What did Aschoff and Weaver (1976) do and find?
Aschoff and Wever (1976) placed participants in an underground WWII bunker with artificial light but no natural light and a complete lack of environmental and social cues. They found that most participants soon settled into a sleep/wake cycle of between 24 and 25 hours, although some rhythms were as long as 29 hours.
What did Folkard et al (1977) do?
Folkard et al. (1977) demonstrated how children who had stories read to them at 3pm showed superior recall and comprehension after a week compared to children who heard the same stories at 9am.
What did Gupta (1991) find?
Gupta (1991) found improved performance on 1Q tests when participants were assessed at 7pm as opposed to 2pm and 9am.
What are the strengths of circadian rhythms?
What are the limitations of circadian rhythms?
What are infradian rhythms?
An infradian rhythm are rhythms that take longer than 24 hours to complete.
There are two examples we are going to look at, the menstrual cycle (periods) and seasonal affective disorder (SAD).
What is the menstrual cycle?
This is an example of an IR.
It is governed by monthly changes in hormone levels
These regulate ovulation
Typical cycle is 28 days but normal range is 24 to 35 days
Rising levels of the hormone oestrogen cause the ovary to develop an egg.
After ovulation progesterone helps the womb grow thicker
Readying the body for pregnancy
What did Stern and McClintock (1998) do and find?
Evidence suggests that it may be influenced by exogenous factors.
The cycles of other women could affect the cycle.
Stern and McClintock (1998) demonstrate how cycles of women may synchronise. (women researchers)
Samples of pheromones were gathered from 9 women at different stages of their cycle.
[they wore cotton pads in their arm pits] frozen in alcohol and placed on the upper lip of a female recipient.
68% of women experienced changes to their cycle – the pheromone brought them closer to the cycle of their odour donor.
What is Seasonal Affective Disorder (SAD)?
Depressive disorder, with seasonal pattern of onset.
Described / diagnosed as a mental health condition by the DSM 5.
As with other symptoms of depression its characterised by persistent low mood, disinterest in general activity and life.
Often referred to as the ‘winter blues’ as symptoms are triggered in the winter months when the number of daylight hours decreases.
85. What causes SAD?
Psychologists have hypothesised that the hormone melatonin is implicated in the cause of SAD. During the night, the pineal gland (see next spread) secretes melatonin until dawn when there is an increase in light. During winter, the lack of light in the morning means this secretion process continues for longer. This is thought to have a knock-on effect on the production of serotonin in the brain - a chemical that has been linked to the onset of depressive symptoms.
