infradian and ultradian rhythms

Question 1

what are infradian rhythms?

Answer 1

a biological rhythm that lasts longer than 24 hours, they can be weekly, monthly or annually

Question 2

one example of an infradian rhythm

Answer 2

the female menstrual cycle
- regulated by hormones that either stimulate the uterus or promote ovulation
- ovulation occurs halfway through the cycle, lasting 16-32 hours
- a usual cycle lasts 28 days, but there is considerable variation

Question 3

another example of an infradian rhythm

Answer 3

seasonal affective disorder (SAD)
- seasonal variation in mood
- governed by a yearly cycle
- claimed that melatonin (secreted by the pineal gland at night) is partially responsible

Question 4

evaluate infradian rhythms
1/4

Answer 4

research suggests the menstrual cycle is somewhat governed by exogenous zeitgebers. reinberg examined women who spent 3 months in a cave with only a lamp for light. her menstrual cycle shortened to 25.7 days. demonstrates the effect of external factors (lack of light) on infradian rhythms (menstrual cycle)

Question 5

evaluate infradian rhythms
2/4

Answer 5

russell et al found females’ cycles became synchronised via odour exposure, sweat from one group was rubbed onto the lips of another group, they were separate but their cycles synchronised. this suggests external factors should be considered when investigating infradian rhythms (as pheromones affected cycle synchronisation) and a more holistic approach should be taken.

this synchronisation can be evolutionarily advantageous, as the synchronisation of pregnancies means childcare can be split among mothers

Question 6

evaluate infradian rhythms
3/4

Answer 6

research suggests infradian rhythms like the menstrual cycle regulate behaviour. penton-volk et al found women preferred feminized faces when least fertile, and masculine faces when most fertile. this indicates women’s sexual behaviour is motivated y infradian rhythms, highlighting the importance of studying them relating to behaviour

Question 7

evaluate infradian rhythms
4/4

Answer 7

evidence supports the role of melatonin in SAD. terman found the SAD rate is higher in northern places where winter nights are longer (e.g. 10% of people in new hampshire in usa, and 2% in southern florida). suggests SAD is somewhat affected by light, an exogenous zeitgeber, resulting in increased melatonin levels

Question 8

what are ultradian rhythms?

Answer 8

• last fewer than 24 hours
• found in the pattern of human sleep
• this cycle alternates between REM and NREM sleep and has 5 stages
• it repeats about every 90 mins during the night

Question 9

sleep cycle stages

Answer 9

• stages 1-4 are NREM and stage 5 is REM
• stages 1 and 2 are light sleep, brainwave patterns get slower, alpha waves progress to theta waves
• stages 3 and 4 are deep sleep, its difficult to wake someone up, associated with slower delta waves
• stage 5 is REM (dream sleep), the body is paralysed and brain activity resembles that of an awake person

Question 10

what is another type of ultradian rhythm?

Answer 10

appetite or meal patterns: people will eat 3 meals a day and their appetite rises and falls due to food consumption

Question 11

evaluate ultradian rhythms
1/3

Answer 11

individual differences play a role in studying sleep cycle patterns. tucker et al found differences between participants for the duration of each stage (particularly 3 and 4), demonstrating there may be innate individual differences in ultradian rhythms that must be focused on during research. since the study was done in a controlled lab, differences cant be attributed to other factors.

Question 12

evaluate ultradian rhythms
2/3

Answer 12

research methodology may mean that results don’t give an accurate conclusion for ultradian rhythms. to investigate sleep patterns, participants are subjected to a level of control and must be attached to monitors to measure the rhythms. this may be invasive and make them sleep in a way different to normal. so investigating ultradian rhythms like the sleep cycle is hard as the lack of ecological validity can cause false conclusions

Question 13

evaluate ultradian rhythms
3/3

Answer 13

the case of randy gardener shows the flexibility of ultradian rhythms. he stayed awake for 264 hours, experiencing issues like blurred vision and disorganised speech, but coped okay with the sleep loss. after he slept for just 15 hours, only recovering 25% of his lost sleep in several nights. suggests the flexibility of the different stages of the sleep cycle and the rhythms variable nature