biological rhythms

Question 1

endogenous pacemaker

Answer 1

internal mechanism that controls cycles. biological clock

Question 2

exogenous zeitgebers

Answer 2

external factors that affect our biological rhythms.

originate from outside the individual

Question 3

circadian rythms

Answer 3

rhythms that last a day (24 hours), daily. examples; the sleep wake cycle, hormone secretion.

Question 4

infradian rhythms

Answer 4

occur over a period longer than a day.

for instance human menstrual cycle, or birds’ migration patterns (which are annual a.k.a circraanual)

Question 5

ultradian rhythms

Answer 5

occur in periods of time shorter than 24 hours.

for instance sleep cycles

Question 6

The sleep wake cycle

Answer 6

• assume around 24 hours asheavily based on day light patterns and other exogenous zeitgebers.
• also can be assumed its dependent on biological endogenous pacemaker

Question 7

Michael Siffre

Answer 7

-spent 6 months living in Texan caves
-all exogenous zeitgebers were removed, biological clock allowed to roam freely, i.e. eating and sleeping whenever his body demanded (natural inclinations).
-he was wired up and physiological functions such as heart rate monitored.
-at first his sleep-wake cycle was errative but settled in to a 25 hour pattern.
EVAL
-one person case study so sample is very limited.
- living conditions were unnatural, uncontrolled factors such as loneliness may have impacted his circadian rhythms, and ultimately the findings of the study.

Question 8

SCN’s role in biological rhythms

Answer 8

• small part of the hypothalamus
• responsible for maintenance of circadian rhythms
• lies just above the optic chasm which means it can quickly recieve info from the photoreceptor cells in the retina
• the SCN generates its own rhythms. This impacts the pineal gland that releases the hormone melatonin in low light levels, causing a state of sleepiness.

Question 9

SCN’s role evidence

Answer 9

• rats with lesioned SCN had their circadian rhythms completely disrupted.
• chickens biological clocks go with dawn break

Question 10

Human menstrual cycle

Answer 10

• infradian
• goverened by hormones (endogenous biological factor) oestrogen and progesterone work to an endogenous pattern under the control of the pituitary gland.

Question 11

Human sleep rhythm

Answer 11

• ultradian
• each sleep cycle lasts about 90 minutes
• comprised of a number of stages, repeating on average 5-6 times
• each stage is different in terms of brain activity (viewed on an EEG machine)
• sleep can be divided into REM and non-REM
• Non-REM: first 2 stages are light sleep, 3rd and 4th stages are SWS and are deeper stages of sleep
• stage two is often followed by a periof of REM sleep

Question 12

Human sleep rhythms evidence

Answer 12

• Biological clocks seem to be the main control mechanism for the stages of sleep
• When the SCN is lesioned squirrel monkeys their sleep cycles and stages were severely disrupted
• Exogenous factors impact sleep- light levels, drugs, temperature
• one study found that alcohol disrupts sleep, However, only one dose of alcohol was used so may not be generalisable to real life/other patterns of alcohol use

Question 13

Shift work

Answer 13

• disrupts the normal links between the human biological clock and the external zeitgebers people experience.
• meal patterns, social life and minor things like TV viewing are all disrupted

Question 14

benefits of studying shift work

Answer 14

prevent accidents occurring i.e. circadian trough, a period of time where workers reach peak tiredness between 2am-6am.

Question 15

different types of shift patterns

Answer 15

-earlies, lates and night shifts- rapid rotating system

Question 16

HORNE (shift patterns)

Answer 16

• earliers, lates and nights are good as workers often get a period of 24 hours between shifts
• BUT hard for our body to adjust to constantly changing.
• on slower rotating systems it is easier for the bosy to adjust
• it is easier for shift workers to rotate in systems that go forward, this extends the day

Question 17

Impacts of shift work

Answer 17

• circadian trough
• poor quality sleep and sleep deprivation, build up of sleep debt
• big individual differences in coping with shift work. i.e. the older you are the harder it is
• social disruption
• LONG TERM: suggest shift work is linked with CHD and cancer. Those working shift work had a 3 fold increase of CHD (men) howver, these studies do not always control for job type. demands

Question 18

lessening the effects of shift work

Answer 18

HORNE suggests:
-moderate amount of caffeine to help with alertness
-short naps no longer than 15 minutes
-brighter light levels
-phase delay: go to bed later get up later, easier than phase adance
CZEISLER , MOORE-EDE, COLEMAN:
-workers on rotating shifts most dislike aspects of work that disregard and disrupt normal bodily rhythms and sleep wake physiology
-schedules that take account of circadian rhythms had the most satisfied workers, with better health

Question 19

Jet lag

Answer 19

• tiredness and sleep discturbance resulting from disruption of body’s normal biological rhythm
• occurs flying E –> W or vice versa
• HORNE: stress, climate and delays and contribute to the impact of jet lag

Question 20

impact of jet lag

Answer 20

• day time sleepiness
• fatigue
• impaired alertness
• trouble maintaining sleep

Question 21

HORNE (larks,owls)

Answer 21

larks deal with jet lag better

Question 22

Lessening the effects of jet lag

Answer 22

DRUGS
-sleeping pills: HORNE - ineffective, leads to grogginess, possibly worsen jet lag
-melatonin: alleviate jet lag, only likely if taken as dusk/ night due to interactions between melatonin and the biological clock
-SPITZER: jet lagged Norwegian doctors- melatonin had no effect, their medical knowledge may have impacted the findings
-an independent study found melatonin to infact be effective, particularly in east bound travel over 5 hours.
-caffeine: one study found caffeine and melatonin to have a positive impact on jetlag, caffeine particularly for day time sleepiness
DAY LIGHT:
-travellers should go out in day light for first few hours after travel - suppresses the surge of melatonin
ADAPTING:
-as soon as possible adapting to local customs and zeitgebers

Question 23

Conservation of energy

Answer 23

WEBB

(evolutionary approach) inactivity to conserve energy levels. heart rate and temp decrease

Question 24

evidence for conservation theory

Answer 24

-small animals have higher metabolic rates and lose heat faster. of WEBB were correct we would also expect these animals to sleep more. ZEPELIN: found a positive correlation between sleep length and metabolic rate. This is limited as there are many factors that can influence sleep not just metabolic rate and body size (not all animals fit in to this pattern)

Question 25

foraging theory

Answer 25

-animals sleep more if they have a nutrient rich diet as they have to spend less time foraging.

Question 26

evidence for foraging

Answer 26

pandas eat bamboo which is low in nutrients, they spend up to 16 hours a day eating. animals like cats and dogs who eat nutrient rich food do not eat continuously

Question 27

food scarcity

Answer 27

sleep should increase when food is scarce. animals have a greater need for conserving energy

Question 28

evidence for food scarcity

Answer 28

BERGER and PHILLIPS: found this to be correct, sleeping more and decreasing body temp in times of food scarcity

Question 29

avoidance or predators

Answer 29

prey may sleep more to ensure safety from predators. animals tend to sleep in darkness when most vulnerable -not the most adaptive, it would seem that a quiet state of alertness would be more effective

Question 30

evidence for avoidance of predators

Answer 30

ALISON and CICHETTI: animals slept less in the day if in danger. 39 species, found a negative correlation between amount of sleep and level of environmental danger However, correlation doesnt always prove causality Rabits and moles sleep similar amounts of time despite the facts moles are exposed to typically less danger.

Question 31

restoration theory as evaluation of conservation theory

Answer 31

there is such diversity in species' sleeping habits, if conservation theory were correct you expect much less variation

Question 32

restoration theory

Answer 32

rest to restore the body to full psychological and physiological capacity

Question 33

OSWALD restoration theory

Answer 33

patients recovering from CNS injuries or drug overdose slept more than healthy individuals and had more REM. suggest the role of REM is for brain repair -may repair the brain through protein synthesis. -in particular growth hormones are released in SWS. This may explain why newborns (who grow quickly) and children sleep more than adults.

Question 34

HORNE restoration theory

Answer 34

- sleep deprived individuals. - sleep recovery was concentrated in stage 4 and REM sleep. - These 2 forms of sleep were critical and 'core sleep' - the other stages are 'optional sleep' - core sleep is when the body restores and replenishes.

Question 35

Evidence for restoration theory

Answer 35

-Randy Gardiner case study -EMPSON: deprived sleepers of REM sleep. on nights where they were allowed REM sleep, REM rate was 50% higher -MORGANE REM sleep seems to restore neurotransmitters in the brain HOWEVER other scientists believe this is not true as REM involves neural activity, so we would expect neurotransmitters to be used and not made

Question 36

Non-REM sleep

Answer 36

stage 1: relaxed, heart rate slows. EEG shows theta waves, slow waves, eyes may role and muscles relax stage 2: EEG patterns of 'sleep spindles' short bursts of high frequency activity stage 3: delta waves which are large in amplitude and slow. body temp and heart rate slow further stage 4: delta activity, deep sleep, hard to wake

Question 37

REM sleep

Answer 37

- REM - high frequency brain waves - small amplitude beta waves - completely relaxed muscles - heart rate and resps become faster and more erratic - dreams more likely to be reported - EEG patterns similar to when awake but all muscles are relaxed everything paralysed except eyes, paradoxical sleep

Question 38

babies/newborns sleep

Answer 38

Newborns sleep around 18 hours a day in no particular pattern. 50-60% of sleep is REM. May be that REM sleep is important for neurotransmitter restorations and synthesis of the brain-helping the brain to become more organised. As foetuses we have more REM sleep than at any other point in our life.

Question 39

children's sleep

Answer 39

REM sleep decreases with age. At age 2 REM sleep only accounts for around 20-25% of sleep. At age 5 children have settled into a pattern of around 10-12 hours sleep and rarely take naps.

Question 40

adults' sleep

Answer 40

Have around 8 hours sleep per night. However there are big individual differences. Around the age of 45 REM sleep is about 15-25% of sleep. Studies have suggested that the purpose of REM is to process the day's events and new learning. Which may explain why it decreases with age.

Question 41

sleep in old age

Answer 41

6-7 hours of sleep per night. Sleep is more fragmented due to a reduction in the amount of deeper stages of sleep. Some studies suggest that in people over 90 there is no deep sleep. May be due to melatonin reduction. REM sleep may be proportionate to young people. Less REM sleep as learning less.