biological rhythms- ultradian and infradian

Question 1

ultradian rhythms:

Answer 1

less than 24 hours

stage 1 & 2- light sleep. Brainwave patterns slower & more rhythmic. Alpha waves and progress to theta waves

stage 3 & 4- deep sleep, difficult to wake someone up. Associated with slower delta waves

stage 5- REM sleep, the body is paralysed (stops person acting out their dreams), brain activity resembles an awake person

cycle repeats every 90 minutes, can experience up to 5 full cycles a night.

Question 2

infradian rhythms:

Answer 2

more than 24 hours

female menstrual cycle:
ovulation occurs half way through cycle when oestrogen levels are at their highest, after ovulatory phase progesterone levels increase.

SAD (seasonal affective disorder):
in winter months the days are shorter meaning less sun. More melatonin is produced, meaning less serotonin and low moods.

Question 3

ultradian limitation: way in which the research is conducted may tell us little

however, lab experiment

Answer 3

P: way in which the research is conducted may tell us little
E: participants have to be attached to monitors when investigating sleep patterns.
E: this may be invasive and lead them to sleep differently to their ordinary cycle
L: shows research into ultradian rhythms lacks ecological validity.
HOWEVER, as this study was a lab experiment, it lacks ecological validity and the results can’t be generalised to the target population when it comes to research into ultradian rhythms

Question 4

ultradian limitation: case study suggests ultradian rhythms are flexible

Answer 4

P: case study suggests ultradian rhythms are flexible
E: someone stayed awake for 11 days and experiences lots of problems (blurred vision, disorganised speech) however they did cope well with the sleep loss.
E: after he slept for 15 hours and recovered only 25% of lost sleep. Interestingly, he recovered 70% of Stage 4 sleep, 50% of his REM sleep, and very little of the other stages.
L: shows the flexibility of ultradian rhythms when it comes to research into ultradian rhythms.

Question 5

infradian (menstrual cycle) evaluation:
it is to some extent governed by exogenous zeitgebers

however, case study

Answer 5

P: Research suggests that the menstrual cycle is, to some
extent, governed by exogenous zeitgebers (external
factors).
E/E: a researcher examined a women who spent 3 months in a cave with only a small artificial light. He noted that her menstrual cycle shortened from the usual 28 days to 25.7 days.
L: This result suggests that the lack of light (an exogenous zeitgeber) in the cave affected her menstrual cycle, and therefore this demonstrates the effect of external factors
on infradian rhythms.
HOWEVER, as this was a case study and was only based on one female, the results cant be generalised to all females when it comes to research into infradian rhythms

Question 6

infradian (SAD) evaluation: Evidence supports the role of melatonin in SAD.

Answer 6

P: Evidence supports the role of melatonin in SAD.
E/E: researcher found that the rate of SAD is more common in Northern countries where the winter nights are longer. e.g. found that SAD affects roughly 10% of people living in New
Hampshire (a northern part of the US) and only 2% of residents in southern Florida.
L: These results suggest that SAD is in part affected by light (exogenous zeitgeber) that results in increased
levels of melatonin.