4.2.2 BIOLOGICAL RHYTHMS

Question 1

what are endogenous pacemakers?

Answer 1

the body’s internal ‘clocks’ that regulate many biological rhythms

Question 2

what are exogenous zeitgebers?

Answer 2

external cues which may affect our biological rhythms
eg) the effect of light on the sleep/wake cycle

Question 3

what are circadian rhythms?

Answer 3

• operate on a 24 hour cycle which is reset by levels of light

eg) sleep / wake cycle and core body temperature

• dictate when we should be awake and sleeping

Question 4

what is the suprachiasmatic nucleus (SCN)?

Answer 4

• in the hypothalamus
• detects the level of light present and then uses this info to coordinate the activity of the entire circadian system

Question 5

what is melatonin?

Answer 5

plays a role in ‘triggering’ sleep by responding to a decrease in the levels of light

Question 6

what is an example of desynchronisation of circadian rhythms?

Answer 6

• jet lag

Question 7

sleep rhythm dips at points in the day
when is it at it’s strongest?
what makes the dips less intense?

Answer 7

strongest sleep drive = 0200-0400 and 1300-1500

• if we have sufficient sleep the dips are less intense

Question 8

the work of Siffre supports circadian rhythms
what was it and what does it suggest?

Answer 8

• in all of his studies, his free-running biological rhythm settled to 25 hours but this altered as he aged with the occasional 48-hour cycle
• only thing influencing him underground was his internal body clock
• left the cave in mid-September 1962 but through it was mid-August
• suggets the human body clock relies on exogenous zeitgebers to help it keep time
  -> without these factors our body clock can extend, making us believe a day is longer than it is

Question 9

what’s a limitation of the work of Siffre?

Answer 9

• it’s a case study
• cannot be generalised beyond the single participant

Question 10

what is an infradian rhythm?

Answer 10

• rhythms that take longer than 24 hours
  -> so there’s a frequency of less than one day
• eg) menstrual cycle, Seasonal Affective Disorder

Question 11

what is the menstrual cycle and how long is it typically?

Answer 11

• government by monthly changes in hormone levels which regulate ovulation
• cycle refers to time between first day of period, when the womb lining is shed - to the day before the next period
• typical cycle length = approximately 28 days (24-35 = normal)

Question 12

what happens during the menstrual cycle?

Answer 12

• during cycle, rising levels of oestrogen cause ovary to develop and egg and release it (ovulation)
• after ovulation, progesterone helps womb lining grow thicker, readying the body for pregnancy
• if pregnancy doesn’t occur, the womb lining sheds (= period)

Question 13

is the menstrual cycle endogenous or exogenous?

Answer 13

• an endogenous system
• but research shows it can be affected by exogenous factors

Question 14

what did McClintock 1998 do?

Answer 14

• studied 29 women with history of irregular periods
• samples of pheromones were gathered from 9 of them at different stages in their menstrual cycle
  -> via a cotton pad under their armpit
• this was worn for 8 hours to ensure pheromones were picked up
• then treated with alcohol and frozen
  -> + rubbed on the upper lip of other ppts

day 1
- cotton pads from start of cycle were applied to all 20 women

day two
- given a cotton pad from the 2nd day of the cycle

Question 15

what did McClintok 1998 find?

Answer 15

found 68% of women experienced changes to their cycle which bought them closer to the cycle of their ‘odour donor’

• this was labelled as the MCCLINTOCK EFFECT

Question 16

what is Seasonal Affective Disorder (SAD)?

Answer 16

• SAD is in the DSM-5 as a recognised mental disorder
• melatonin has been implicated in the cause of SAD
  -> during nighttime, pineal gland secretes melatonin until dawn when there’s an increase in light
• during winter, the light means the secretion continues for longer
• this is thought to then affect the production of serotonin

Question 17

what are ultradian rhythms?

Answer 17

• biological rhythms that you have more than once a day
• biological rhythms that take less than 24hrs to complete, may often occur more than once over the course of a day

eg) stages of sleep

Question 18

what are the 5 recognised stages of sleep?

Answer 18

• stages 1 and 2 are the sleep escalator
• stages 3 and 4 consist of the delta waves of deep sleep
• stage 5 is REM sleep, the stage in which dreaming occurs according to research

Question 19

how long does each stage span for?
how many are completed?
what does each stage differ from the other in?

Answer 19

• 5 distinct stages that span 90 minutes
• you must complete multiple cycles throughout the night
• each stage has different brainwave activity linked to it

Question 20

what happens in stage 1?

Answer 20

• light sleep
• muscle activity slows down
• occasional muscle twitching
• brainwave patterns are slower and more rhythmic (alpha + theta)

Question 21

what happens in stage 2?

Answer 21

• breathing pattern and heart rate slows
• slight decrease in body temperature

Question 22

what happens in stage 3?

Answer 22

• deep sleep begins
• brain begins to generate slow delta waves
  -> (but they still have a greater amplitude than earlier wave patterns)

Question 23

what happens in stage 4?

Answer 23

• very deep sleep
• rhythmic breathing
• limited muscle activity, brain produces delta waves

Question 24

what happens in stage 5?

Answer 24

• Rapid Eye Movement (REM)
• brainwaves speed up and dreaming occurs
• muscles relax and heart rate increases
• breathing is rapid and shallow
• body is paralysed yet brain activity speeds up significantly in a way that resembles the awake brain (REM)

Question 25

what did Dermot and Kleitman do in 1957 that supports ultradian rhythms?

AO3

Answer 25

• monitored sleep patterns of 9 adult ppts in a sleep lab
• brainwave activity was recorded on an EEG and the researchers controlled for the effects of caffeine and alcohol
• REM activity during sleep was highly correlated with the experience of dreaming
• brain activity varied according to how vivid dreams were
• participants woken during dreaming reported very accurate recall of their dreams
• therefore shows distinct stages of sleep, like REM

Question 26

what is a limitation of Derment and Kleitman’s research?

AO3

Answer 26

• carried out in the 1950s so may lack temporal validity
• eg) use of phones didn’t exist at the time of the research, which nowadays may interfere with people’s ultradian rhythms
• this means new research should be undertaken on this topic

Question 27

what’s a limitation of the MCCLINTOCK effect?
AO3

Answer 27

• was a field study so may hold several extraneous variables
  eg) diet, exercise, pollution, could have interfered with the findings
• ethical issues
  -> conducting research on infradian rhythms, deliberately disturbing a woman’s natural menstrual cycle could have far-reaching effects
  eg) her fertility, emotional state)
  which the researchers wouldn’t be able to predict

Question 28

fill in this table

Answer 28