Uktradian Rhythms Flashcards
What are ultradian rhythms
They span a period of less than 24 hours, an example being the five sleep stages. Human sleep follows a pattern of alternating between rapid eye movement (REM) sleep (which is stage 5) and non rapid eye movement (NREM) sleep (which is stages 1 2 3 4). The cycle repeats every 90 mins
What has EEG shown?
Each sleep stage has a distinct EEG pattern. During deep sleep, their brainwaves slow and their breathing and heart rate decrease. During thr fifth stage, the EEG pattern resembles that of an awake person. It is that stage in which dreaming occurs
Stage 1 and 2 is light sleep, starting with alpha waves and then progressing to theta waves
Stage 3 and 4 are deep sleep and delta waves
Stage 5 is REM and here the body is paralysed and brain activity resembles that of an awake person
What did kleitman refer to the 90 min cycle as?
He referred to it as a the Basic Rest Activity Cycle. He suggested that this 90 min cycle continues when we are awake during the day, and rather than moving through the sleep stages, we actually move progressively from a state of alertness to a state of physiological fatigue. Research says The human mind can focus for about 90 mins before running out of resources and losing concentration.
Strengths of ultradian rhythms?
+Ericsson et al found support for ultradian rhythms (BRAC). They studied a group of elite violinists and found that among this group , practice sessions were limited to 90 mins at a time. They napped to recover from practice. Same pattern found amongst athletes, chess yutes and writers.
+ .research support from dement and kleitmam for stages of sleep £ supporting the ultradian rhythms
Weakness ultradian rhythms
- tucker et al suggested that there are individual differences in ultradian rhythms whihc are biologically determined and may even be genetic. Participants were studied over a period of 11 days and nights in a lab environment. The researchers assessed sleep duration, time taken to fall asleep and the amount of time in each sleep stage. There were differences in all of these characteristics,
What are infradian rhythms ?
Rhythms that span a period longer than 24hrs. They may last weeks months or even a year. Example is the menstrual cycle, lasting around a month. There are considerable variations in the length of this cycle, with some experiencing a 23 days cycle, and others a 36. The average however is 28.
What regulates the menstrual cycle
Regulated by hormones that either promote ovulation or stimulate uterus fertilisation. Ovulation occurs roughly halfway through the cycle when oestrogen peaks and lasts for a round 16-32 hours. After the ovulatory phase, progesterone increases in prep for the possible implantation of an embryo in the uterus.
Strengths infradian
There is research to suggest that infradian rhythms such as the menstrual cycle are important regulators of behaviour. Penton volk et al found that women expressed a preference for feminised faces at the least fertile stage of their menstrual cycle, but a more masculine one at their most fertile point. This indicates that women sexual behaviour is motivated by their infradian rhythms, highlighting the importance,of studying these rhythms in relation to human behaviour.
Weaknesses infradian
Processes like The menstrual cycle is not only governed by infradian rhythms. When several women of child bearing age live together and do not take oral contraceptives, their cycles synchronise. Another study whereby samples of sweat were collected from one group of women and rubbed onto the upper lip of another , their cycles also synchronised, suggesting that synchronisation is affected by pheromones. Pheromones are chemical substances produced and released into the environment by an animal that affects the behaviour of others of the same spexiesm
