Biological rhythms

Question 1

What are circadian rhythms and a example?

Answer 1

Biological rhythms with a cycle of once in a 24 hour period- regulate a number of processes such as the sleep-wake cycle

Question 2

What is the exogeneous zeitgeber that influences sleep-wake cycle?

Answer 2

light

Question 3

What is our endogenous pacemaker that governs the sleep-wake cycle and its role?

Answer 3

-internal ‘body clock= suprachiasmatic nucleus
-SCN lies above the optic chiasm which provides information from the eye about light

Question 4

Outline Siffre’s cave study and findings

Answer 4

-spent two months in cave to study effect of his own biological rhythm
-deprived of exposure to natural light & sound
-In each case his ‘free-running’ biological rhythm settled down to around 25 hrs
-fall and woke on regular schedule

Question 5

Outline Aschoff and Wever’s research

Answer 5

-convinced pp’s to spend four weeks in a WW2 bunker deprived of natural light

Question 6

What did Aschoff and Wever find?

Answer 6

-all but one pp (29hrs) displayed a circadian rhythm between 24 & 25 hrs
-suggest natural sleep-wake cycle longer than 24hr but entrained by EZ’s associated with 24hr day (mealtimes, daylight etc.)

Question 7

Outline Folkard’s study

Answer 7

-studied group of 12 people who agreed to live in dark cave for 3 weeks
-went to bed when clock said 11:45 and rose when it was 7:45
-researchers gradually sped up clock (pp’s not aware)
-so an apparent 24hr day eventually only lasted 22hrs

Question 8

What did Folkard find?

Answer 8

-only one pp was able to adjust to new regime
-suggest existence of strong free-running circadian rhythm cannot be overridden by EZ’s

Question 9

Why does research into the sleep/wake cycle have real world application?

Answer 9

-helps us to understand consequences that occur when our circadian rhythms are disrupted
-night workers have reduced concentration at 6am( circadian trough) =mistakes/accidents
-shift workers 3x likely to develop heart disease than typical work patterns

Question 10

What is a counterpoint for real world application of sleep/wake cycle research ?

Answer 10

-investigating effects of shift work= correlational methods
-difficult to establish cause (disrupted s/w cycle) & effect (negative)
-may not be biological factors
-Solomon ^divorces rates in shift workers= missing out on family events as well as deprived sleep

Question 11

Why are generalisations using research into circadian rhythms difficult to make?

Answer 11

-studies =small samples (low pop validity)
-Czeisler» found individual differences in s/w cycles varying from 13-65hrs
-Duffy et al» some people have natural preference for going to bed early (larks) some are the opposite (owls)

Question 12

What are Infradian rhythms and examples?

Answer 12

Biological rhythms with a frequency of less than one cycle in a 24 hour period e.g. menstrual cycle & seasonal affective disorder

Question 13

what is the menstrual cycle

Answer 13

• it is governed by monthly changes in hormone levels which regulate ovulation
  -cycle refers to the first day of a women’s period to the day before her next period
  -cycle takes approximately 28 days to complete

Question 14

What happens during the menstrual cycle? endogenous systems

Answer 14

-increased oestrogen levels cause ovary to develop an egg and release it
-after ovulation increased progesterone levels help the womb lining to grow thicker- preparation for pregnancy
-if pregnancy does not occur the egg is absorbed into the body, the womb lining sheds away and leaves the body (menstrual flow)

Question 15

outline study that shows that the menstrual cycle may be influenced by exogeneous factors?

Answer 15

Stern & McClintock - menstrual cycle may synchronise through influence of pheromones
-studied 29 people with history of irregular periods
-samples of pheromones gathered from 9 at different stages of menstrual cycle via a cotton pad placed in armpit (8 hours)
-pads treated with alcohol & frozen to be rubbed on upper lip of other pp’s
68% of women experienced changes to their cycle

Question 16

What is seasonal affective disorder and its symptoms?

Answer 16

-SAD is a depressive disorder which has a seasonal pattern of onset
-Sad is a particular type of infradian rhythm called circannual rhythm -subject to yearly cycle
-main symptoms= low mood, lack of activity & interest in life

Question 17

Why is SAD often referred to as the ‘winter blues’?

Answer 17

-symptoms are triggered during winter months, when daylight hours becomes shorter

Question 18

What is the endogenous pacemaker for SAD?

Answer 18

endogenous pacemaker= melatonin
-during winter, lack of light in morning =secretion of melatonin longer
- has a knock on effect on production of serotonin -linked to depressive symptoms

Question 19

Why are menstrual synchrony studies flawed? (Stern & McClintock)

Answer 19

-study could have been subject to confounding variables
- other factors that may have influenced the women’s menstrual cycles ( stress, diet, exercise)
-Also relied on women self reporting the onset & duration of their cycles
-low internal validity

Question 20

Why is synchronisation an adaptive strategy?

Answer 20

Stern and McClintock’s study is said to have some evolutionary value
- ancestors it may have an advantageous for women to menstruate together and get pregnant at the same time
- new babies would have been part of a social group who cared for one another & had access to breast milk if mother died at birth» improving their chances of survival

Question 21

What are ultradian rhythms and example?

Answer 21

A biological rhythm that has a cycle of more than once in a 24 hour period such as the stages of sleep

Question 22

What are the stages of sleep?

Answer 22

-Psychologist have identified five distinct stages of sleep that span together approximately 90 minutes
-each stage characterized by different level of brain wave activity

Question 23

Describe stage 1 and 2

Answer 23

-Light sleep
-brain waves have high frequency and low amplitude (alpha waves)
-stage 2 - alpha waves continue but their are random changes in patterns called spindle fibres

Question 24

Describe stage 3 and 4

Answer 24

-deep sleep
-brain waves are delta waves with low frequency and high amplitude

Question 25

Describe stage 5 (REM sleep)

Answer 25

-brain is paralysed
-brain produces theta waves
-eyes occasionally move around (REM)

Question 26

Strength of research into ultradian rhythms

Answer 26

-improved understanding of age-related changes in sleep
-sleep scientists have observed that SWS (3 & 4) reduces with age
-Cauter et al- the resulting sleep deficit may explain various issues in old age such as reduced alertness
-To increase SWS medication may be used

Question 27

What is a limitation of Ultradian rhythms?

Answer 27

-there is a significant variation between people
-Tucker et al found large differences between participants in terms of the duration of each stage ( 3&4)
-differences likely to be biologically determined