CIRCADIAN RHYTHMS

Question 1

● What is a circadian rhythm?

Answer 1

A biological rhythm that lasts 24 hours

Question 2

● What is the main endogenous pacemaker for the sleep-wake cycle?

Answer 2

Suprachiasmatic nucleus (SCN)

Question 3

● What does SCN stand for?

Answer 3

Suprachiasmatic nucleus

Question 4

● What are exogenous zeitgebers?

Answer 4

External environmental cues

Question 5

● Give one example of an exogenous zeitgeber in the sleep wake cycle

Answer 5

Light

Question 6

● What are endogenous pacemakers?

Answer 6

Internal body clocks

Question 7

● Which hormone is involved in sleep regulation?

Answer 7

Melatonin

Question 8

● What gland releases melatonin?

Answer 8

Pineal gland

Question 9

● What is entrainment?

Answer 9

The resetting of biological clocks by external cues

Question 10

● What rhythm is influenced by both pacemakers and zeitgebers?

Answer 10

Sleep-wake cycle

Question 11

▲ How does light affect the SCN?

Answer 11

It resets the internal body clock

Question 12

▲ Why is melatonin important for sleep?

Answer 12

It makes us feel tired

Question 13

▲ What is the effect of the absence of zeitgebers?

Answer 13

Rhythm becomes longer than 24 hours

Question 14

▲ What did Siffre’s study show about the sleep-wake cycle?

Answer 14

It continued but adjusted to about 25 hours

Question 15

▲ What happened to Siffre’s cycle in the cave?

Answer 15

It became longer than 24 hours

Question 16

▲ How does the SCN maintain circadian rhythms?

Answer 16

By regulating melatonin production

Question 17

▲ What social cues influence the sleep-wake cycle?

Answer 17

Meal times and social interaction

Question 18

▲ What causes disruption of circadian rhythms?

Answer 18

Jet lag or shift work

Question 19

▲ What did DeCoursey’s study with chipmunks show?

Answer 19

SCN damage disrupted sleep-wake cycles

Question 20

▲ What are the consequences of circadian disruption?

Answer 20

Poor reasoning, tiredness, digestive issues

Question 21

✪ How does Siffre’s cave study support the role of endogenous pacemakers?

Answer 21

Sleep-wake cycle persisted without external cues

Question 22

✪ What limitation does Siffre’s study have regarding ecological validity?

Answer 22

Highly controlled setting not reflective of real life

Question 23

✪ Why does DeCoursey’s study lack generalisability to humans?

Answer 23

Animal bias due to differences in biological systems

Question 24

✪ How does DeCoursey’s study support the role of endogenous pacemakers?

Answer 24

Loss of SCN disrupted rhythms despite natural environment

Question 25

✪ How does the interactionist approach apply to circadian rhythms?

Answer 25

Both pacemakers and zeitgebers maintain the rhythm

Question 26

✪ What does the sleep disruption in shift work suggest about zeitgebers?

Answer 26

External cues are essential for synchronising the clock

Question 27

✪ Why might Siffre’s extended rhythm suggest zeitgebers are necessary?

Answer 27

Without them, the body deviates from a 24-hour cycle

Question 28

✪ How does the role of light as a zeitgeber increase the validity of exogenous factors?

Answer 28

It resets the SCN and aligns sleep

Question 29

✪ What is a weakness of using animal studies to understand circadian rhythms?

Answer 29

Limited applicability due to species differences

Question 30

✪ Why is the SCN considered a key endogenous pacemaker?

Answer 30

It regulates melatonin based on light information from the eyes

Question 31

● What resets the SCN?

Answer 31

Light

Question 32

● What is the name for internal biological clocks?

Answer 32

Endogenous pacemakers

Question 33

● What does the pineal gland do at night?

Answer 33

Releases melatonin

Question 34

● What happens to alertness after evening meals?

Answer 34

Decreases

Question 35

● What kind of cycle is the sleep-wake cycle?

Answer 35

Circadian

Question 36

▲ What happens to melatonin levels in darkness?

Answer 36

They increase

Question 37

▲ Why is melatonin called the sleep hormone?

Answer 37

It promotes drowsiness

Question 38

▲ How can blackout curtains help maintain rhythms?

Answer 38

They reduce artificial light exposure at night

Question 39

▲ What behavioural advice helps reduce jet lag?

Answer 39

Eat and sleep at local times

Question 40

▲ How does social interaction act as a zeitgeber?

Answer 40

It influences when we feel alert or sleepy

Question 41

✪ Why does the shift from a 24 to 25-hour cycle in isolation matter?

Answer 41

It shows endogenous pacemakers are not exactly 24 hours

Question 42

✪ How do exogenous zeitgebers help maintain a 24-hour cycle?

Answer 42

They entrain pacemakers to external time

Question 43

✪ What is the effect of conflicting zeitgebers in shift work?

Answer 43

Circadian disruption and reduced cognitive function

Question 44

✪ How might modern lighting reduce sleep quality?

Answer 44

It interferes with melatonin production

Question 45

✪ Why is it problematic to isolate pacemakers in real life?

Answer 45

They interact constantly with external cues