Circadian rhythms

4 types of rhythms

Biological rhythms

Ultradian rhythms

Infradian rhythms

Circadian rhythms

What is a biological rhythm?

Changes in body that conform to cyclical time periods

What is:

Changes in body that conform to cyclical time periods

Biological rhythm

What is an Ultradian rhythm?

Occurs many times during the day

What is

Occurs many times during the day

Ultradian rhythm

What is an infradian rhythm?

Takes longer than a day

What is a rhythm that takes longer than a day?

Infradian rhythm

What is a circadian rhythm?

Has a 24 hour cycle

What rhythm has a 24 hour cycle?

Circadian rhythm

Who experimented with effect of EZ on circadian rhythms?

Siffre (1972)

When did Siffre do his experiment?

1972

Aim of Siffre (1972)

Effect of EZ on circadian rhythm

Method of Siffre (1972)

1. Spent 6 months in a cave with no natural light or cues for day and night

2. Artificial light in cave to help him navigate

3. Settled into a sleep/wake cycle of 25 hours and missed a month

What is

1. Spent 6 months in a cave with no natural light or cues for day and night

2. Artificial light in cave to help him navigate

3. Settled into a sleep/wake cycle of 25 hours and missed a month

Siffre (1972) method

Siffre (1972) findings (2)

-Lack of cues altered his sleep/wake cycle

-Left cave and thought it was a month earlier than it was

What is

-Lack of cues altered his sleep/wake cycle

-Left cave and thought it was a month earlier than it was

Siffre (1972) findings

Conclusion of Siffre (1972)

-Sleep/wake cycle might be more than 24 hours but EZ needed to keep it at 24

-Supports idea we have free running circadian rhythm regulated by EPs

What is

-Sleep/wake cycle might be more than 24 hours but EZ needed to keep it at 24

-Supports idea we have free running circadian rhythm regulated by EPs

Siffre (1972)

3 experiments about sleep/wake cycle

-Siffre (1972)

-Aschoff + Weber (1976)

-Folkard (1985)

When did Aschoff + Wever do their experiment?

1976

Method of Aschoff + Wever (1976) (4)

1. Studied Ps living in a bunker with no windows and only artificial light (that they could turn on and off whenever they wanted)

2. Ps settled into sleep/wake cycle of 25-27 hours

3. Suggests EZ of light needed to regulate sleep/wake cycle to 24 hours

4. All but 1 P settled into 25-27 hour cycle - individual differences

What is

1. Studied Ps living in a bunker with no windows and only artificial light (that they could turn on and off whenever they wanted)

2. Ps settled into sleep/wake cycle of 25-27 hours

3. Suggests EZ of light needed to regulate sleep/wake cycle to 24 hours

4. All but 1 P settled into 25-27 hour cycle - individual differences

Aschoff + Wever (1976) method

Individual differences of sleep/wake cycle

Researcher found morning and evening people have different circadian rhythms

What sleep/wake cycle did all but 1 P settle into in Aschoff + Wever (1976)

25-27 hours

What year did Folkard do his experiment?

1985

Folkard (1985) method (3)

-12 Ps live in a dark cave for 3 weeks

-Sleep when clock says 11:45. Wake when clock says 7:45

-Researchers gradually sped up clock until a day was 22 hours

What is

-12 Ps live in a dark cave for 3 weeks

-Sleep when clock says 11:45. Wake when clock says 7:45

-Researchers gradually sped up clock until a day was 22 hours

Folkard (1985) method

How many Ps in Folkard (1985) and how long in the cave?

12

3 weeks

How long was a day at the end of Folkard (1985)?

22 hours

Folkard (1985) findings

-Only 1 P could comfortably adjust to new regime

→ suggests existence of strong free running circadian rhythm that cant be easily overridden by EZ

Limitation of circadian rhythm reserach

Small groups or individuals used

What is desynchronisation?

Circadian rhythm disruption

What is the name for circadian rhythm disruption?

Desynchronisation

Who is desynchronisation common for?

Night shift workers

Effects of disrupted biological rhythms

Disrupted sleep patterns

Higher anxiety

Less alertness

Night shift workers are

3X more likely to develop heart disease

What is homeostasis?

Maintaining equilibrium

How does homeostasis link to sleep/wake cycle?

If individual wake for awhile, tells body need for sleep to balance with energy consumption

Unsuccessful homeostasis - organism dies

What is

If individual wake for awhile, tells body need for sleep to balance with energy consumption

Unsuccessful homeostasis - organism dies

How homeostasis links to circadian rhythm

2 examples of circadian rhythms

Sleep/wake cycle

Body temperature

Body temperature times

Lowest early morning

Highest early evening

What is

Lowest early morning

Highest early evening

Body temperature times

Body temperature and sleep

Sleep when core temperature starts to drop

End of sleep cycle temp starts to rise

Temp when you sleep

Sleep when core temperature starts to starts to drop

Temp when you wake up

Core temperature starts to rise at end of sleep cycle

How much does core temp vary by in the day?

2C

Link to temp and cognitive abilities

Warmer = better cognitive abilities

Researcher showed children read to at 3pm had better comprehension than those read to at 9am

What temp has better cognitive abilities?

Warmer

Limitation of circadian rhythms

Biologically reductionist

Limitation of circadian rhythms - Biologically reductionist

P: Biologically reductionist

E: Behaviourists would say bodily rhythms influenced by other people and social norms eg: sleep at dark coz thats how society is

C: Therefore reductionist as it only considers biological part

Strengths of circadian rhythms (3)

-Created better understanding of consequences of desynchronisation

-Circadian rhythms coordinate lots of basic bodily processes such as heart rate

-Research support

Strength of circadian rhythms - Research support

-Ralph (1990)

-Siffre (1972)

→ counter arguments for both

Strength of circadian rhythm - Created better understanding of consequences of desynchronisation

P: Created better understanding of consequences of desynchronisation

E: Night workers had reduced conc. around 6am. Also, 3X more likely to develop heart disease due to lack of quality sleep + stress of adjusting sleep/wake cycle

C: Research has economic implications

Strength of circadian rhythms - Circadian rhythms coordinate lots of basic bodily processes such as heart rate

P: Circadian rhythms coordinate lots of basic bodily processes such as heart rate

E: Effect on pharmacokinetics -how well drugs are absorbed and distributed in body coz research shows there’s times where effectiveness peaks

C: Led to development of guideline dosing for range of drugs eg: anti epileptic