Endogenous Pacemakers and Exogenous Zietgebers

Question 1

What are endogenous pacemakers?

Answer 1

They are internal biological mechanisms that make up the body clock

Question 2

What is the suprachiasmatic nuclei?

Answer 2

It is the influential endogenous pacemaker.

Question 3

Where does the SCN in the hypothalamus receive it’s information from?

Answer 3

The sense organs - how light/dark is it from the retinas

Question 4

Information from our Sense organs synchronises our

Answer 4

Biological rhythms with the outside world

Question 5

Cues from the environment are called…

Answer 5

Exogenous zeitgebers

Question 6

Cues from the environment play an important role in

Answer 6

Regulating time

Question 7

The importance of these cues on the sleep/wake cycle has been investigated by…

Answer 7

research that has manipulated internal and external cues

Question 8

It’s difficult to manipulate the actual physiology of humans and therefore…

Answer 8

The biology of endogenous pacemakers has been demonstrated by animal studies

Question 9

Ralph et al date

Answer 9

1990

Question 10

What did Ralph et al (1990) do?

Answer 10

Removed the SCN of genetically abnormal hamsters which only had 20 hour cycles

Question 11

The importance of the SCN in sleep wake cycle can be seen by

Answer 11

The findings that when it’s connected to a damaged retina

Question 12

If the retina is damaged…

Answer 12

Circadian rhythms disappear

Question 13

The removed SCN were transplanted into rats that had no abnormality - 24 hour cycles

Answer 13

The damaged SCN caused the rhythm to shorten

Question 14

because the transplanted SCN changed the hamsters body clock, this shows…

Answer 14

that the SCN is important in the body clock

Question 15

Siffre date

Answer 15

1975

Question 16

what did Siffre do?

Answer 16

he studied his own body clock after spending 6 months in a cave with no natural light or cues

Question 17

what did Siffre’s body clock change to?

Answer 17

25-30 hours

Question 18

how long did Siffre think he was in the cave for?

Answer 18

one month

Question 19

how long was Siffre actually in the cave for?

Answer 19

six months

Question 20

The body clock still functions without

Answer 20

External cues but the circadian rhythm can vary as a consequence

Question 21

What did Siffre observe when he was 60 in 1999?

Answer 21

His body clocked ticked more slowly then when he was young

Question 22

because Siffre’s body clock was slower when he got older, this shows the problem with case studies

Answer 22

they may be rich in detail but individual factors may prevent general conclusions being drawn

Question 23

Duffy et al date

Answer 23

2001

Question 24

what did Duffy et al say?

Answer 24

people have a natural preference for sleeping and rising - they can be categorized by larks or owls

Question 25

larks are

Answer 25

people who go to bed early and rise early

Question 26

owls are

Answer 26

people who go to bed late and rise late

Question 27

who replicated Siffre’s findings?

Answer 27

Aschoff and Weaver (1976)

Question 28

what did Aschoff and Weaver do?

Answer 28

they convinced a a group to spend four weeks in a WW2 bunker deprived of natural light

Question 29

Aschoff and Weaver (1976) participants circadian rhythm during the experiment

Answer 29

24-25 hours - one participants rhythm extended to 29 hours

Question 30

The role of exogenous zeitgebers was investigated by

Answer 30

Folkard et al (1985)

Question 31

How many participants did Folkard remove natural light from?

Answer 31

12

Question 32

How many weeks did Folkard remove the natural light from the 12 participants for?

Answer 32

3

Question 33

What did Folkard manipulate?

Answer 33

The environmental cues

Question 34

What times did the participants wake up and go to sleep.

Answer 34

7: 25AM
11: 45PM

Question 35

Without participant knowledge, what did Folkard do?

Answer 35

Increased their body clock so the day was 22 hours

Question 36

How many participants could not adjust to Folkards new rhythm?

Answer 36

Just one

Question 37

Folkard concluded that

Answer 37

Natural light sources and mechanical exogenous zeitgebers are vital for keeping the individuals to a 24 hour cycle

Question 38

Folkard showed that our natural circadian rhythm is

Answer 38

Flexible and can differ between individuals

Question 39

Problems with research conducted by
Ralph et al (1990)
Siffre (1975) 
Aschoff and Weaver (1976)
Folkard et al (1985)

Answer 39

Validity

Question 40

What’s the validity problem with all this research?

Answer 40

The confounding variable of the access of artificial light when deprived of natural light

Question 41

What is a strength of the research conducted by
Ralph et al (1990)
Siffre (1975) 
Aschoff and Weaver (1976)
Folkard et al (1985)

Answer 41

It has important applications - we have a better understanding of desynchronisation

Question 42

At what time to night shift workers experience a period of reduced concentration?

Answer 42

6am

Question 43

At 6am, what is more likely to happen?

Answer 43

Accidents

Question 44

What does the circadian rhythm coordinate?

Answer 44

Heart rate
Digestion
Hormone levels

Question 45

By having a better understanding of Heart rate, Digestion and Hormone levels has allowed us a better understanding of

Answer 45

Pharmokinetics

Question 46

What is Pharmokinetics?

Answer 46

How drugs are absorbed and distributed