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A-Level Psychology > Lesson 12 - Endogenous Pacemakers and Exogenous Zeitgebers > Flashcards

Lesson 12 - Endogenous Pacemakers and Exogenous Zeitgebers Flashcards

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1
Q

What are endogenous pacemakers?

A

Internal biological rhythms

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2
Q

What are exogenous zeitgebers?

A

External cues and factors

E.g. light

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3
Q

What is the role of endogenous pacemakers and exogenous zeitgebers?

A

To reset our biological rhythms every day

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4
Q

What is the most important endogenous pacemakers?

A

SCN

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5
Q

What is the SCN?

A

A tiny cluster of nerve cells in the hypothalamus

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6
Q

What role does the SCN play?

A

An important role in generating circadian rhythms

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7
Q

What does the SCN do?

A

Acts as the master clock

Linking other brain regions controlling sleep and arousal

And controlling all other biological clocks throughout the body

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8
Q

What do the neurons in the SCN do?

A

Neurons in the SCN synchronise with each other

So that their target neurons elsewhere in the body receive time-coordinated signals

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9
Q

Why are the peripheral clocks controlled by the SCN?

A

They can maintain a circadian rhythm but not for very long

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10
Q

Why can the SCN maintain a circadian rhythm?

A

It has a built in circadian rhythm

Only needs resetting when external light levels change

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11
Q

How does the SCN receive information about light levels?

A

Optic nerve

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12
Q

What happens when the biological clock is running slow?

A

Morning light shifts the clock

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13
Q

What does the SCN also regulate?

A

Regulates the manufacture and secretion of melatonin in the pineal gland
Via the interconnecting neural pathway

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14
Q

How does the SCN control melatonin levels?

A

SCN sends a signal to pineal gland -> increase production and secretion of melatonin at night and decrease it as light levels increase in morning

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15
Q

How does melatonin work?

A

Induces sleep by inhibiting the brain mechanisms that promote wakefulness

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16
Q

Folkard
1996

Endogenous pacemakers
+

A

Folkard studied university student Kate Aldcroft

Spent 25 days in laboratory with no access to exogenous zeitgebers which RESET SCN
e.g. daylight

Core temperature rhythm was still at 24 hours after 25 days

17
Q

Folkard
1996

A

Kate Aldcroft’s sleep-wake cycle extended to 30 hours

Periods of sleep as long as 16 hours

Shows we do need external influences to maintain our biological rhythm

18
Q

What does exogenous mean?

A

Anything with origins outside the organism

19
Q

What is the long definition for exogenous zeitgebers?

A

Environmental events that are responsible for maintaining the biological clock of an organism

20
Q

What is the most important zeitgeber for animals?

A

Light

21
Q

How does light synchronise the activity of the body’s organs and glands?

A

Receptors in the SCN are sensitive to changes in light levels during the day

Use this information to synchronise the activity of the body’s organs and glands

22
Q

What resets the biological clock each day?

A

Light

Keeps it on a 24 hour cycle

23
Q

What is melanopsin?

A

A protein in the retina of the eye

24
Q

What does melanopsin do?

A

Sensitive to natural light

Critical for resetting internal biological clock

25
Q

What happens when people travel to a different country or do night shift?

A

Endogenous pacemakers try to impose their inbuilt rhythm of sleep, circadian rhythm

This is out of synchrony with exogenous zeitgeber, light

26
Q

What do disrupted biological rhythms lead to?

A

Disrupted sleep patterns

Increased anxiety

Decreased alertness and vigilance

27
Q

Skene and Arendt
2007

Exogenous zeitgebers
+

A

Found vast majority of blind subjects with some light perception have normal circadian rhythms

People without light perception show abnormal circadian rhythms

28
Q

Burgess et al
2003

Exogenous zeitgebers
+

A

Exposure to bright light prior to an east-west flight

Decreased time needed to adjust to local time in arrival

29
Q

Vetter et al
2011

Exogenous zeitgebers
+

A

Compared sleep-wake cycle and activity-rest patterns of 2 groups over a five-week period

One group in normal warm artificial light; other group experienced artificial blue light

All participants kept a daily sleep log and wore movement-measuring devices

Participants under the warm light synchronised their circadian rhythms with the natural light of dawn

Participants exposed to blue light synchronised their patterns to office hours

A-Level Psychology (17 decks)

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