Circadian rhythms Flashcards
1
Q
What is a biological rhythm?
A
- Distinct patterns of changes in body activity that conform to cyclical time periods.
- Biological rhythms are influenced by internal body clocks and external changes to the environment
2
Q
What are our internal body clocks?
A
- endogeneous pacemakers
3
Q
What are external changes in the environment?
A
- exogeneous zeitgebers
4
Q
What is a circadian rhythm?
A
- A type of biological rhythm that lasts 24 hours
5
Q
What are two types of circadian rhythms?
A
- the sleep/wake cycle
- core body temperature
6
Q
What is the sleep wake cycle?
A
- The sleep wake cycle ensures that we sleep and feel drowsy at night and feel awake during morning
- This is governed by daylight which is an important exogenous zeitgeber
- Our sleep wake cycle is also governed by an internal pacemaker which is our internal body clock
7
Q
What is our internal body clock called?
A
- The superchiasmatic nucleus (SCN) which lies above the optic chiasm and provides information from our eyes about light
- Exogeneous zeitbegers such as light can reset the SCN
- darkness signals the scn and causes the pineal gland to secrete melatonin, causing tiredness
8
Q
What was siffres cave study?
A
- Micheal Siffre is a self - styled caveman who had spent extended periods underground to study the effects on his biological rhythms
- Siffre deprived himself of natural light and sound but had access to natural light but had a team bring him food and drink.
- siffre recorded his sleep/wake cycle and emerged out of the cave in mid - september but believed it to be mid - august
- A decade later he repeated it but for 6 months
- He found that his free - running biological rhythm settled to 25 hours but he had a regular sleep/wake cycle
9
Q
What does this tell us about biological rhythms?
A
- biological rhythms show that the sleep/wake cycle is slightly longer than 24 hours but is entrained by exogeneous zeitgebers like daylight
- However, we have strong internal body clocks that can not be easily overridden by exogeneous zeitgebers such as different sleep and waking times. This is showcased by Simon Folkard
10
Q
What was other research into biological rhythms?
A
- Similar results to siffre were recorded by Aschoff and Wever who convinced a group of participants to spend 4 weeks in a WW2 bunker deprived of natural light
- All but one participants whose sleep/wale cycle extended to 29 hours all had a circadian rhythm between 24 - 25 hours
11
Q
Who did research into endogenous pacemakers?
A
- Simon Folkard
- Simon Folkard studied a group of 12 participants who agreed to live in a dark cave for 3 weeks, sleeping when the clock said 11:35 and waking up at 7:45am
- however, over time they sped the clock up to a 22 hour sleep/wake cycle
- However, only one participant was able to keep up with this 22 sleep/wake cycle showing how heavily circadian rhythms are
12
Q
What is a strength of circadian rhythms?
A
- We can use circadian rhythms to improve medical treatments
- Circadian rhythms co - ordiante a number of basic processes such as heart rate, digestion and hormone level
- The rise and fall of these levels had led to chronotherapeutics
- chronotherapeutics is the study of how medical treatments can be administered in a way that corresponds to a persons biological rhythms.
- For example, aspirin prevents heart attacks which are more likely to occur during day.
- So circadian rhythms can increase the effectiveness of drug treatments
13
Q
What is another strength of circadian
rhythms?
A
- Circadian rhythms provide an understanding of the adverse consequences of when circadian rhythms are disrupted
- For example, night workers who work shifts have a decreased rate of concentration at 6am, this is because they expierence a circadian trough which is explained by the circadian rhythm
- This shows that we can predict a lot of mistakes that occur at these times
- Also, research has shown that shift workers are 3 times more likely to develop heart disease
- This shows that research into sleep wake cycles can have real world economic implications and educate people about how to manage productivity
- However, there are may be other factors that contribute to poor concentration so it may be difficult to establish cause and effect
14
Q
What is a limitation of circadian rhythms?
A
- studies into circadian rhythms are difficult to generalise
- for example, Aschoff and Wever and Siffre are all based on small samples of participants and sleep, wake cycles differ based on individual
- A study by Duffy et al revealed that some people are naturally night owls or larks and therefore had differing sleep/wake cycles
