biological rythms Flashcards
(46 cards)
1
Q
what are circadian rythms
A
- 24 hour body cycles
- driven by our body clocks
- synchronised by the superchiasmatic nuclei (SCN) –> this pacemaker must be reset so bodies are in tune with outside world
2
Q
explain how light affects the sleep-wake cycle
A
- light resets body’s exogenous pacemaker
- rods and cones in retina of eye detect light
- light stimulates SCN which suppresses production of melatonin (sleepy hormone)
3
Q
explain how homeostasis plays a role in the sleep-wake cycle
A
- when we have been awake for long periods homeostasis drives feelings of sleepiness as we have used lots of energy during wakefulness
- the homeostasis drive for sleep increases throughout the day, peaking in the late evening when most ppl fall asleep
4
Q
the internal circadian clock is described as ‘free-running’ - what does this mean?
A
free running rythms refer to the circadian rhythm assumed by an individual when external cues do not guide their sleep
5
Q
describe the supporting evidence for free running circadian rhythms regarding Micheal Siffre’s case study
A
- Siffre subjected himself to 6 months living underground in order to study his own circadian rhythm
- his circadian rhythm extended to 25 hours –> he left the cave thinking it was a month earlier than it was
6
Q
describe the supporting evidence for free running circadian rhythms regarding Folkard’s research
A
- studied 12 ppts who lived in cave for 3 weeks, with set bedtimes + waking up times
- throughout the study, researchers gradually sped up clocks so apparent 24hr day was reduced to 22hrs
- not one ppt adjusted well to the new regime
- increases validity for free-running CR that cant be overridden by external changes
7
Q
describe core body temperature as an indicator of the circadian rhythm
A
- sleep occurs when core temp begins to drop, and body temp starts to rise during last hours of sleep
- small drop in body temp also occurs between 2pm and 4pm which may explain why ppl feel sleepy in the afternoon
8
Q
describe an A03 point of core temperature as a circadian rhythm
A
- evidence suggests body temp may affect CR more than light
- SCN transforms info about light levels into neural messages that set the body temp
- even small changes to temp can send powerful msgs to body clock
- Buhr found these fluctuations set timings of cells in body, and can cause tissue to become either active or inactive
9
Q
describe hormone production as a type of circadian rhythm
A
- production release of melatonin follows this rhythm, with peak levels occurring during the hours of darkness
- melatonin encourages feelings of sleep –> when its dark, more melatonin is produced
10
Q
what are some examples of circadian rhythms
A
- sleep-wake cycle
- core body temperature
- hormone production
11
Q
what are some overall A03 points of circadian rhythms
A
- individual differences❌
- methodological issues❌
- real life application✅
12
Q
A
13
Q
describe an A03 point of circadian rhythms regarding individual differences
A
- sleep wake cycles differ from person to person
- Czeisler found that CR cycles varies from 13 to 65 hours
- later even Siffre observed his sleep/wake cycle had slowed down since he was young
- difficult to create a nomothetic law
14
Q
describe an A03 point of circadian rhythms regarding methodological methods
A
- in most studies pps were isolated from variables such as clocks and natural light, but they weren’t isolated from dim artificial light
- originally it was believed that dim light wont affect CR
- however Czeisler found even presence of dim artificial light could alter CR
- lowers validity
15
Q
describe an A03 point of circadian rhythms regarding real life application
A
- chronotherapeutics = study of how timings affect drug treatments
- research has shown that time at which meds are taken can have significant impact on efficiency
- EG –> most vulnerable time for heart attacks is morning - CTPS allow patients to take drugs at night for it to remain dormant until vulnerable time period
16
Q
describe infradian rhythms
A
- duration of over 24 hrs –> could be weekly, monthly or even annually
- occurs more than every 24 hrs but less than yearly
17
Q
describe ultradian rhythms
A
cycles that last less than 24 hours
- may occur multiple times a day
18
Q
what are some examples of Infradian rhythms
A
- monthly - menstrual cycle
- annual - SAD = circannual rhythm
19
Q
what are some overall A03 points of infradian rhythms
A
- research support
- evidence suggests menstrual cycle may also be affected by exogenous cues
- research suggests menstrual cycle may affect mate choice
20
Q
describe an A03 point of infradian rhythms regarding research support
A
- Terman found that the rate of SAD is more common in Northern countries where winter nights are longer
- EG - it affects about 10% of people living in New Hampshire (in the North of the USA) but only about 2% of people from Southern Florida
- This suggests that SAD is in part affected by light that results in increased levels of melatonin
21
Q
describe an A03 point of infradian rhythms regarding evidence suggesting that menstrual cycle may also be affected by exogenous cues
A
- MC is controlled by endogenous systems –> hormones
- however exogenous cues can also control it
- when several women live tgt their MC syncs
- Russel’s study - sweat samples collected and rubbed on upper lip of women in 2nd group
- groups were kept separate yet cycles synced with their ‘odour donor’
- suggests MC can be affected by pheremones
22
Q
describe an A03 point of infradian rhythms regarding research suggesting that menstrual cycle may affect mate choice
A
- Penton-Voak et al suggests different preferences at different cycle stages
- women expressed preference for ‘slightly feminised’ male faces when picking long term partner
- however, in ovulatory phase women showed preference for more masculine faces
- this preference believed to represent preference for kindness and cooperation in parental care in LT mates, but preference for males with ‘good genes’
23
Q
describe the Basic Rest Activity Cycle (BRAC)
A
- Kleitman referred to the 90 min cycle found during sleep as BRAC
- he suggested cycle continues even when we are awake but instead we move through periods of alertness and physiological fatigue
24
Q
describe stage 1 of the sleep stages
A
- theta waves
- light sleep
- muscle activity slows down
25
describe stage 2 of the sleep stages
- sleep spindles
- breathing patterns and heart rate slows down
- body temp lowers
26
describe stage 3 of the sleep stages
- large delta waves
- deep sleep begins
27
describe stage 4 of the sleep stages
- more large delta waves
- very deep sleep
- rhythmic breathing
28
describe stage 5 of the sleep stages
- REM --> brainwaves speed ups nd dreaming occurs
- muscles relax and HR increases
- breathing in rapid and shallow
29
what are some overall A03 points of ultradian rhythms
- research support✅
- individual differences❌
- methodological issues❌
30
describe an A03 point of ultradian rhythms regarding research support
- research shows humans can concentrate for no more than 90 mins
- Ericsson studied group of elite violinists + found that their producgice sessions were max 90 mins
- supports kleitmans claim that fatigue is characteristic of BRAC cycle
- Ericsson highlighted importance of naps/recovery, noting that best musicians napped often
31
describe an A03 point of ultradian rhythms regarding individual differences
- Tucker shows there may be biological differences in sleep patterns
- studied participants over 11 nights in strict lab environment --> assessed sleep duration and time in each sleep stage
- differences were most notable in deep sleep
- Tucker says its down to biology rather than environment
32
describe an A03 point of ultradian rhythms regarding methodological issues
- lab setting = controlled EVs
- this means researcher can exclude temporary variables such as temp or noise
- however lab studies involve being attached to complicated machinery --ppts wont sleep normally
- lowers validity
33
what do endogenous pacemakers allow us to do
- keep pace with changing cycles in the environment
- most important pacemaker in human beings is the suprachiasmatic nucleus (SCN)
34
describe the suprachiasmatic nucleus (SEN)
- bundle of cells located in hypothalamus
- influential in maintaining circadian rhythms
- nerve fibres connected to eye cross --> receives info about light directly from structure
- continues even when eyes are closed - enables nbio clock to adjust to changing daylight patterns
35
describe the role of the pineal gland
- SCN passes info on day length and light to pineal gland
- during night, PG increases production of melatonin --> chem that induces sleep
36
what are some overall A03 points for endogenous pacemakers
- research support✅
- real life application✅
37
describe an A03 point for exogenous pacemakers regarding research support
- Morgan bred hamsters to have CR of 20hrs rather than 24hrs
- SCN neurons were transplanted from abnormal hamsters to normal hamsters
- normal hamsters then displayed same abnormal CR of 20hrs
CP --> cant generealise to humans; cant confidently assume that it applies to humans
38
describe an A03 point for exogenous pacemakers regarding real life application
- Touitou argued that exposure to artificial light at night disrupts CR which has adverse effects on health
- LED bulbs enriched with blue light are active on circadian clock, supressing melatonin
- as a result sleep becomes irregular and shortened
- can change routine to increase sleep health
39
what are exogenous zeitgebers
environmental events that are responsible for entraining the biological clock of an organism
40
what are some examples of exogenous zeitgebers
- light
- social cues
41
describe light as an exogenous zeitgeber
- resets the bodys endogenous pacemaker (SCN)
- plays a role in maintaining sleep/wake cycle
- indirect influences such as hormone secretion and blood circulation
42
describe how light affects are body clocks
- rods and cones in retina of eye detect light to form visual images
- however, 3rd type of light-detecting cell gauges brightness to help reset biological clock
43
describe social cues as an exogenous zeitgeber
- social stimuli such as mealtimes also act as zeitgeber
- schedules are a key influence, such as set meal times
44
what are some overall A03 points of exogenous zeitgebers
- research support - Siffre ✅
- real life application✅
45
describe an A03 point of exogenous zeitgebers regarding research support
- Micheal Siffre emerged from cave and thought it was a month earlier
- his 24hr sleep cycle had increased due to lack of exogenous cues - light and social cues
- provides support that external f actors influence internal rhythm
46
describe an A03 point of exogenous zeitgebers regarding real life application
- Burgess found that exposure to bright light prior to an east to west flight decreased jet lag
- results show that light exposure is a powerful exogenous cue + can be used to overcome jet lag
