6.7: Exogenous zeitgebers and the sleep/wake cycle

Question 1

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks)

Answer 1

Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues

Question 2

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.

Answer 2

Exogenous zeitgebers reset our biological clocks through a process known as entrainment

Question 3

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus,

Answer 3

Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors

Question 4

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Answer 4

Light is a key zeitgeber in humans

Question 5

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.

Answer 5

It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle

Question 6

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.

Answer 6

Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation

Question 7

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

Answer 7

In human infants, the initial sleep/wake cycle is pretty much random

Question 8

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.

Answer 8

At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained

Question 9

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.

Answer 9

The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes

Question 10

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

First AO3 PEEL paragraph

Answer 10

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle

Question 11

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
Example

Answer 11

For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was

Question 12

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
What does this suggest?

Answer 12

This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was

Question 13

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
Who is this further supported by?

Answer 13

This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours

Question 14

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
What does this demonstrate?

Answer 14

This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them

Question 15

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them.
What does this also emphasise?

Answer 15

This also emphasises the importance of exogenous zeitgebers, as these internal clocks were not entrained or accurate without them

Question 16

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them.
This also emphasises the importance of exogenous zeitgebers, as these internal clocks were not entrained or accurate without them.
What does this highlight?

Answer 16

This highlights the impact of external factors on bodily rhythms

Question 17

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them.
This also emphasises the importance of exogenous zeitgebers, as these internal clocks were not entrained or accurate without them.
This highlights the impact of external factors on bodily rhythms.

Second AO3 PEEL paragraph

Answer 17

The second AO3 PEEL paragraph is that However, studies of the sleep/wake cycle tend to involve studies of single individuals, as in the case of Siffre, or small groups of participants, as in Aschoff and Wever’s experiment

Question 18

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them.
This also emphasises the importance of exogenous zeitgebers, as these internal clocks were not entrained or accurate without them.
This highlights the impact of external factors on bodily rhythms.

The second AO3 PEEL paragraph is that However, studies of the sleep/wake cycle tend to involve studies of single individuals, as in the case of Siffre, or small groups of participants, as in Aschoff and Wever’s experiment.

Answer 18

The people involved may not be representative of the wider population and this limits the extent to which meaningful generalisations can be made due to individual differences

Question 19

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them.
This also emphasises the importance of exogenous zeitgebers, as these internal clocks were not entrained or accurate without them.
This highlights the impact of external factors on bodily rhythms.

The second AO3 PEEL paragraph is that However, studies of the sleep/wake cycle tend to involve studies of single individuals, as in the case of Siffre, or small groups of participants, as in Aschoff and Wever’s experiment.
The people involved may not be representative of the wider population and this limits the extent to which meaningful generalisations can be made due to individual differences.
Why is this also?

Answer 19

This is also because individual cycles can vary, in some cases from 13 to 65 hours (Czeisler et al., 1999)

Question 20

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them.
This also emphasises the importance of exogenous zeitgebers, as these internal clocks were not entrained or accurate without them.
This highlights the impact of external factors on bodily rhythms.

The second AO3 PEEL paragraph is that However, studies of the sleep/wake cycle tend to involve studies of single individuals, as in the case of Siffre, or small groups of participants, as in Aschoff and Wever’s experiment.
The people involved may not be representative of the wider population and this limits the extent to which meaningful generalisations can be made due to individual differences.
This is also because individual cycles can vary, in some cases from 13 to 65 hours (Czeisler et al., 1999).
Who is this supported by?

Answer 20

This is supported by Duffy et al. (2001), who revealed that morning people display a natural preference for going to bed early and waking up early (larks), whereas evening people prefer going to bed late and waking up early (owls)

Question 21

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them.
This also emphasises the importance of exogenous zeitgebers, as these internal clocks were not entrained or accurate without them.
This highlights the impact of external factors on bodily rhythms.

The second AO3 PEEL paragraph is that However, studies of the sleep/wake cycle tend to involve studies of single individuals, as in the case of Siffre, or small groups of participants, as in Aschoff and Wever’s experiment.
The people involved may not be representative of the wider population and this limits the extent to which meaningful generalisations can be made due to individual differences.
This is also because individual cycles can vary, in some cases from 13 to 65 hours (Czeisler et al., 1999).
This is supported by Duffy et al. (2001), who revealed that morning people display a natural preference for going to bed early and waking up early (larks), whereas evening people prefer going to bed late and waking up early (owls).
Who is this further supported by?

Answer 21

This is further supported by Siffre himself, who, after his most recent cave experience in 1999 and aged 60, observed that his internal clock ticked much more slowly than when he was a young man

Question 22

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them.
This also emphasises the importance of exogenous zeitgebers, as these internal clocks were not entrained or accurate without them.
This highlights the impact of external factors on bodily rhythms.

The second AO3 PEEL paragraph is that However, studies of the sleep/wake cycle tend to involve studies of single individuals, as in the case of Siffre, or small groups of participants, as in Aschoff and Wever’s experiment.
The people involved may not be representative of the wider population and this limits the extent to which meaningful generalisations can be made due to individual differences.
This is also because individual cycles can vary, in some cases from 13 to 65 hours (Czeisler et al., 1999).
This is supported by Duffy et al. (2001), who revealed that morning people display a natural preference for going to bed early and waking up early (larks), whereas evening people prefer going to bed late and waking up early (owls).
This is further supported by Siffre himself, who, after his most recent cave experience in 1999 and aged 60, observed that his internal clock ticked much more slowly than when he was a young man.
What does this illustrate?

Answer 22

This illustrates the fact that even when the same person is involved, there are factors that vary which limit the extent to which general conclusions can be drawn

Question 23

Discuss the effect of exogenous zeitgebers on the sleep/wake cycle (16 marks).
Exogenous zeitgebers are external cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle, temperature and social cues.
Exogenous zeitgebers reset our biological clocks through a process known as entrainment.
Thus, sleeping and wakefulness would seem to be determined by an interaction of internal and external factors.

Light is a key zeitgeber in humans.
It can reset the body’s main endogenous pacemaker, the SCN, and thus plays a role in maintenance of the sleep/wake cycle.
Light also has an indirect influence on key processes in the body that control functions such as hormone secretion and blood circulation.

In human infants, the initial sleep/wake cycle is pretty much random.
At about 6 weeks of age, the circadian rhythms begin and by about 16 weeks, most babies are entrained.
The schedules imposed by parents are likely to be a key influence here, including adult-determined mealtimes and bedtimes.

The first AO3 PEEL paragraph is that there is research support for the role of exogenous zeitgebers on the sleep/wake cycle.
For example, when Siffre returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
This suggests that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was.
This is further supported by Aschoff and Wever (1976), who placed participants in an underground WW2 bunker without any external cues and found all but one of the participants (whose sleep/wake cycle extended to 29 hours) to display a circadian rhythm between 24-25 hours.
This demonstrates the existence of circadian rhythms and their endogenous pacemakers (internal clocks), which persisted even without exogenous zeitgebers to influence them.
This also emphasises the importance of exogenous zeitgebers, as these internal clocks were not entrained or accurate without them.
This highlights the impact of external factors on bodily rhythms.

The second AO3 PEEL paragraph is that However, studies of the sleep/wake cycle tend to involve studies of single individuals, as in the case of Siffre, or small groups of participants, as in Aschoff and Wever’s experiment.
The people involved may not be representative of the wider population and this limits the extent to which meaningful generalisations can be made due to individual differences.
This is also because individual cycles can vary, in some cases from 13 to 65 hours (Czeisler et al., 1999).
This is supported by Duffy et al. (2001), who revealed that morning people display a natural preference for going to bed early and waking up early (larks), whereas evening people prefer going to bed late and waking up early (owls).
This is further supported by Siffre himself, who, after his most recent cave experience in 1999 and aged 60, observed that his internal clock ticked much more slowly than when he was a young man.
This illustrates the fact that even when the same person is involved, there are factors that vary which limit the extent to which general conclusions can be drawn.

Third AO3 PEEL paragraph

Answer 23

The third AO3 PEEL paragraph is that