Circadian rhythms

Question 1

What is a biological rhythm?

Answer 1

• 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

Question 2

What are our internal body clocks?

Answer 2

• endogeneous pacemakers

Question 3

What are external changes in the environment?

Answer 3

• exogeneous zeitgebers

Question 4

What is a circadian rhythm?

Answer 4

• A type of biological rhythm that lasts 24 hours

Question 5

What are two types of circadian rhythms?

Answer 5

• the sleep/wake cycle
• core body temperature

Question 6

What is the sleep wake cycle?

Answer 6

• 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

Question 7

What is our internal body clock called?

Answer 7

• 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

Question 8

What was siffres cave study?

Answer 8

• 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 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 for 2 months in the Southern Alps
• A decade later he repeated it but for 6 months in a texan cave
• He found that his free - running biological rhythm settled to 25 hours but he had a regular sleep/wake cycle

Question 9

What does this tell us about biological rhythms?

Answer 9

• 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

Question 10

What was other research into biological rhythms?

Answer 10

• 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

Question 11

Who did research into endogenous pacemakers?

Answer 11

• 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 11:45 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

Question 12

What is a strength of circadian rhythms?

Answer 12

• 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

Question 13

What is another strength of circadian
rhythms?

Answer 13

• 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

C = Solomon found that there are higher divorce rates in shift workers due to the strain of deprived sleep. Therefore it may not be biological influences that create the adverse consequences associated with shift workers

Question 14

What is a limitation of circadian rhythms?

Answer 14

• 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