Biological Rhythms

Question 1

what is a circadium rhythm

Answer 1

a rhythm that lasts for 24 hours

Question 2

give an example of a circadum rhythm

Answer 2

sleep/wake cycle

Question 3

what is an endogenous pacemaker

Answer 3

internal mechanisms that govern biological rhythms

Question 4

what is the endogenous pacemaker involved in the sleep/wake cycle

Answer 4

the suprachiasmatic nucleus (SCN)

Question 5

what are exogenous zeitbegeres

Answer 5

external factors in the eviornment that reset our biologial clocks through entrainment

Question 6

what is the exogenous zeitberger that affects the sleep/wake cycle

Answer 6

light

Question 7

explain how the SCN controls the sleep/wake cycle

Answer 7

• it recieves information about light from the optic chiasm
• the SCN passes on information on day length and light that it recieves to the pineal gland
• the pineal gland will increase the production of melatonin during periods of sleep and inhibits during wakefullness

Question 8

what is the hormone associated with the sleep/wake cycle

Answer 8

melatonin

Question 9

what is an infradian rhythm

Answer 9

rythyms that take longer than 24 hours

Question 10

what are the 2 examples of an infradian rhythm

Answer 10

• menstrual cycle
• Seasonal affective disorder (SAD)

Question 11

explain the menstrual cycle

Answer 11

• takes approximately 28 days to complete
• during each cycle, rising levels of the hormone oestrogen cause the ovary to develop an egg and release it
• after ovulation, the hormone progesterone helps the womb lining to grow thicker which readies the womb for pregnancy

Question 12

explain SAD

Answer 12

• during the night the pineal gland secretes melatonin
• during winter, the lack of light in the morningmeans the secretion process continues for longer
• this affects the serotonin production in the brain

Question 13

give evidence that supports the roe of melatonin in SAD

Answer 13

• terman found the rate of SAD is more common in the northern hemisphere where winter night are longer
• eg, SAD affects 10% of people living in northern USA and 2% of residents in southern USA

Question 14

what is an ultradian rhythm

Answer 14

rythym that takes less than 24 hours to complete

Question 15

what is an examploe of an ultradian rhythm

Answer 15

sleep stages

Question 16

how much sleep stages are there

Answer 16

5

Question 17

explain stages 1 and 2 of sleep

Answer 17

• light sleep, easily woken
• stage 1: brain waves are high frequency and short amplitude - alpha waves
• stage 2: alpha waves continue but random sleep spindles

Question 18

explain stages 3 and 4 of sleep

Answer 18

• deep sleep, difficult to wake
• brain waves have a low frequency and high amplitude - delta waves

Question 19

explain stage 5 of sleep

Answer 19

REM sleep

• body paralysed, brain active
• brain produces theta waves and eyes move around
• dreams most often experiences

Question 20

give research to support the effect of shift work and mistakes

Answer 20

boivin et al

• workers experince reduced concentraion around 6 am
• mistakes more likely

Question 21

how does the circadium rhythm in teenagrs differ to adults

Answer 21

• teenagers have a later circadium rhythm
• melatonin release: teenagers = 10:30pm, adults = 9pm
• melatonin inhibition: teenagers = 9am, adults = 7:30 am

Question 22

give rsearch that contradicts light as an exogenous zeitberger

Answer 22

siffre

• caveman who spent an extended period in a cxave deproved of natural light and sound
• his circadiun rhythm settled to around 25 hours

Question 23

give research that highlights the importance of light as an exogenous zeitberger

Answer 23

campbell and murphy

• light was shone at participants knees at various timkes when they were woken up
• rsearches deviarted the participants circadiun rhythm

Question 24

Summarise the difference between circadian, infradian and ultradian rhythms.

Answer 24

Circadian ≈ 24 h (e.g., sleep/wake); infradian > 24 h (e.g., 28-day menstrual cycle); ultradian < 24 h (e.g., 90-min sleep stages)

Question 25

Name two social zeitgebers that help entrain the human circadian rhythm.

Answer 25

Local meal times and social routines (work/school schedules) act as cues that reset the body clock when light cues are weak.

Question 26

What does “entrainment” mean in biological rhythms?

Answer 26

It is the process by which exogenous zeitgebers reset the endogenous pacemaker, synchronising the internal clock with the external 24-h world.

Question 27

give a PEELH for light as an exogenous zeitberger | limitation

Answer 27

P - contradicting evidence Eg - siffre, caveman who spent extended period in a cave with no exposure to light. his biological rhythm settled to 25 hours Ex - shows light is not important in relation to the biological clock L - the effect of light as an EZ lacks validity H - study conducted on oe person so cannot be generalised

Question 28

# strength evaluate research into circadian rythms

Answer 28

* P - real world application * Eg - boivin et al tracked shift workers and found a clear "circadian trough". concentration and productivity dipped sharply around 6am and error rates spiked * Ex - enables managers to design forward rotating rotas and timed light interventions, reducing accidents and long term health risks * L - this provides tabgible benefits for the workplace giving circadian theory strong extneral validity and social value * H - most studies are correlational, factors such as workload and caffiene also influence alertness

Question 29

# limitation evaluate research into circadian rythms

Answer 29

* P - much evidence relies on small, unrepresentative case studies * Eg - siffre lived alone in a cave with no natural light. his rythm drifted to around 25 hours * Ex - because the samplle was only one person, results may reflect individuals natural sleep pattern not a universal human clock * L - may be misleading to generalise case study findings to the wider population * H - controlled studies still found a robust 24 hour rhythm

Question 30

# strength evaluate research into ultradian rythms

Answer 30

* P - research uses objective, physiological measurements * Eg - dement and kleitman monitered brain activity of nine adults during sleep with EEG and found REM periods were strongly linked to dreaming: 90% of particpants recalled vivid dreams when woken up from REM * Ex - EEG provides a direct, quantitative record of brain waves so the stages are identified without reliance on self report * L - gives the findings high internal validity, which confrims the five stage cycle * H - the studys small lab bases sample may not represent natural sleep

Question 31

# limitation evaluate research into ultradian rythms

Answer 31

* P - research often takes place in artifical settings * Eg - dement and kleitman. particpants slept wired to EEG under observatoin * Ex - the unfamiliar bed and monitering equipment can alter brain activity so the recorded pattern might not match what happens at home * L - lacks ecological validity * H - neweer research finds similiar findings in participants own bedrooms

Question 32

# strebngth evaluate research into infradian rhythms

Answer 32

* P - produced real ,world treatments * Eg - for SAD. eastment showed sitting in front of a 10000 lux light box for 30 minutes relieved depressive symptoms in about 60% of patients * Ex- light therpay works becauise it suppresses melatonin and resets the body clock * L - this gives research high extrnal validity, improving health outcomes * H - follow up studies show high relapse rates the following winter

Question 33

# limitation evaluate research into infradian rythms

Answer 33

* P - studies have poor methodology * Eg - meta analysis by harris et al reviewed 10 synchrony experiments and found once confouding variables were controlled such as diet and stress, cycle alignment was no greater than chance * Ex - because studies rely on small volunterr smaples and self reports, they are vulnerable to bias and coincidence * L - weaken confidenmce in the claims that external cues shape the menstrual cycle * H -

Question 34

# stregth evaluate light as an exogeneous zeitberger

Answer 34

supportinmg evidence. cambpell and murphy knee study