Biological Rhythms

Question 1

Ultradian rhythms

Answer 1

Rhythms that have more than 1 cycle in 24hrs

Question 2

Circadian rhythms

Answer 2

Rhythms that have 1 cycle in 24hrs

E.g. sleep

Question 3

Infradian rhythms

Answer 3

Rhythms that have less than 1 cycle in 24hrs

E.g. menstrual cycle

Question 4

Endogenous pacemakers

Answer 4

Body’s internal clock: biological structures in brain that affect circadian rhythms

Question 5

Suprachiasmatic nucleus (SCN)

Answer 5

Found in hypothalamus in both hemispheres

Group of neurons which regulate actions of pineal gland

Question 6

Pineal gland

Answer 6

Responsive to light

During darkness, converts serotonin into melatonin (chemical that encourages sleep)

It is these changing levels of hormones that seem to affect the rhythms of the body

Question 7

Exogenous zeitgebers

Answer 7

External cues/environmental factors that affect circadian rhythms

Light and social cues

Question 8

Body rhythms

Answer 8

All biological rhythms are controlled by internal biological structures yet they can be affected by external influences

2 factors:
Endogenous pacemakers
Exogenous zeitgebers

Question 9

Research investigating effect of endogenous pacemakers on the sleep-wale cycle

Answer 9

Siffre (1975)

Spent 61 days and nights in an underground cave, deprived of natural daylight

Access to adequate food and drink

During time there, found that his biological rhythm remained regular (e.g. fell asleep and woke up on a regular basis)

But rhythm extended to just over 25 hours

Question 10

Research investigating effect of exogenous zeitgebers on the sleep-wale cycle

Answer 10

Folkard (1985)

In lab experiment, 12 participants agreed to live in dark cave for 3 weeks (deprived from natural daylight), going to bed when clock said 11:45pm and rising when it said 7:45am

Over course of experiment, participants were unaware that experimenters gradually sped up the clock (e.g. from 24 to 22hr cycles)

Found that initially participants circadian rhythms matched the clock but overtime, participants returned to normal 24-25 hr cycle by ignoring clock and going to bed when tired

Question 11

Conclusion of siffre

Answer 11

Sleep-wake cycle is mainly controlled by endogenous pacemakers,

in absence of exogenous zeitgebers e.g. daylight and social cues, SCN works independently on a 25-hr or longer cycle

Our sleep-wake cycle is therefore longer than 24hrs when we have no external cues to help regulate it

Question 12

Conc of folkard

Answer 12

Exogenous zeitgebers (e.g. daylight and social cues) help match our internal timekeeper with external world

E.g. light levels reset body clock so it works to circadian day/night cycle

Question 12

Conc of folkard

Answer 12

Exogenous zeitgebers (e.g. daylight and social cues) help match our internal timekeeper with external world

E.g. light levels reset body clock so it works to circadian day/night cycle

Question 13

Strength of circadian rhythms

Answer 13

Has practical application

Which is when the principles of a study can be applied in real life

This is because research suggests that disrupting our circadian rhythms on a regular basis has negative effects, such as reduced concentration around 6am, making accidents and mistakes more likely

Therefore, due to this research, preventative measures (such as scheduled breaks and rests) have been implemented to reduce accidents from occurring

Question 14

Circadian rhythms weakness

Answer 14

There are individual differences

This is when there is variability between different groups of participants, which most research into circadian rhythms doesn’t account for

For example, research has suggested that cycle length can vary beetween 13 and 65 hours

Additional research suggests differences in cycle onset, which could explain why some people prefer to rise early and go to bed early whereas other people prefer to rise late and go to bed late

This challeneges the concept that circadian rhthms are the same in all of us, and therefore reduces the validity of pieces of research that doesn’t account for these differences

Question 15

Menstrual cycle

Answer 15

Controlled by monthly hormonal changes which regulate ovulation,

a typical cycle takes approximately 28 days (although anywhere between 24 and 35 days is generally considered normal)

Question 16

SAD

Answer 16

Annual rhythm during winter months where there is a lack of light

More melatonin is produced causing persistent low mood, alongside a general pack of activity and lethargy

Question 17

Research investigating infradian rhthms

Answer 17

McClintock (1998)

Lab experiment, 29 women with a history of irregular periods were recruited

Samples of their phermones were taken at different stages of menstrual cycle, via a cotton pad placed under their armpit for 8 hours

Pads then treated with alcohol then frozen

On day 1 of their next cycle, pads taken from another cycle from start of their menstrual cycle was rubbed on upper lip of another participant

Day 2, same participant given a 2nd day’s pad from same odour donor and so on

Found that 68% of women experienced changes to their cycle, which meant they had their period at similar time to their odour donor

Question 18

Strength of infradian rhythms

Answer 18

Has led to practical applications

Which is when …

For example, research which has informed us of the negative effects of infradian rhythms such as SAD, has allowed medical professionals to introduce treatments such as phototherapy, which stimulates a very strong light in morning and evening

These therapies have relived symptoms in up to 60% of sufferers, suggesting research investigating our biological rhythms are beneficial to society

Question 19

Weakness infradian rhythms

Answer 19

Suffers from high extraneous variables

Which is when a method cannot easily control other variables that could affect the DV