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Biopsychology > Circadian rhythms > Flashcards

Circadian rhythms Flashcards

1
Q

What is a biological rhythm?

A

A cycle of changes in bodily processes or behaviour in response to biological ‘body clock’ or external factors.

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2
Q

What are endogenous pacemakers?

A

A biological body clock

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3
Q

What are exogenous zeitgebers?

A

External factors.

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4
Q

Who long does it take for a circadian rhythm to complete?

A

24 hrs.

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5
Q

How many times does a circadian rhythm occur in 24 hrs?

A

Once

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6
Q

What are examples of circadian rhythms?

A
  • Temperature
  • Sleep/wake cycle
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7
Q

How much does our body temperature vary throughout the day?

A

2 degrees centigrade.

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8
Q

What is the main endogenous pacemaker for the sleep/wake cycle?

A

The suprachiasmatic nucleus (SCN)
(nucleus = small group of cells in this context).

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9
Q

Where is the SCN located?

A

The hypothalamus in each hemisphere.

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10
Q

Approximately how many hours does the SCN set for being asleep and awake?

A

Awake: 17
Asleep: 7

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11
Q

How does the SCN receive information about light levels?

A

Via the optic chiasm, connected by nerve cells.

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12
Q

What is the optic chiasm?

A

Where the nerve fibres from the eyes cross.

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13
Q

What gland produces melatonin?

A

The pineal gland.

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14
Q

How does the SCN wake us up or make us tired?

A
  • It detects light levels from light receptors on the eyelids
  • It passes on the information to the pineal gland
  • When light levels are high, it inhibits the production of melatonin
    When the light levels are low, it produces melatonin
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15
Q

What are the two jobs of the SCN?

A
  • To set the sleep/wake cycle to 24hrs
  • To synchronise the cycle with daytime and nighttime.
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16
Q

What is some evidence to support the role of the SCN as the internal body clock?

A
  • Stephen and Zucker, rats
  • Decoursey, chipmunks
17
Q

What is some evidence to support the role of light as an external cue?

A
  • Siffre, living in a cave for 6 months
18
Q

What happened during the experiment on rats by Stephen and Zucker?

A

The lesioned (destroyed) the SCN in rats.
They found circadian rhythms were disrupted. eg: sleep/wake, feeling hungry/thirsty.
The rats no longer had regular eating, sleeping, drinking patterns.
Suggests SNC is in control of circadian rhythms.

19
Q

What happened in Decoursey and his experiments on chipmunks?

A
  • Lesioned the SCN of chipmunks
  • Sleep/wake cycle was disrupted. Chipmunks were awake at night when they would normally be asleep.
  • Suggests SNC controls circadian rhythms not external factors.
20
Q

What are the weaknesses of the animal studies about the SNC?

A

We can’t easily generalise the findings to humans. Biological control of sleep/wake cycle is likely to be more complex in humans.

21
Q

What are the strengths of the animals studies about the SNC?

A

It acted as useful starting point, allowing other researchers to focus their attention on the SNC and its connections to other parts of the brain (optic chiasm, pineal gland).

22
Q

What happened in Siffre’s experiment?

A
  • French geologist lives in a cave for 6 months with artificial light, no external cues (like noise) and no access to the time.
  • Found that his free running sleep/wake cycle had changed to approx. 25hrs and sometimes extended to 48hrs.
23
Q

Evaluation points on Siffre’s experiment.

A
  • It was a case study so can’t easily generalise findings. For some sleep/wake cycle might be shorter than 24hrs.
  • Artificial light could have confounded the experiment, essentially replacing natural light. Could be why his free running body clock was close to 24hrs.
24
Q

What are some applications of the sleep/wake cycle?

A
  • Creating a sleep/wake cycle in babies.
  • Coping with shift work
  • Adjusting to time zones
25
Q

How can babies have their sleep/wake cycles be trained to natural light levels?

A
  • Use blackout blinds at night
  • Lots of light in day
  • Only feeding in the day (where possible)
  • Only playing during day.
    Usually by 16 weeks, the sleep/wake cycle is trained to natural light levels.
26
Q

What can help someone adapt to a night shift?

A

Using mealtimes as a cue for wakefulness. Eg: eating breakfast before shift
Reducing light levels as much as possible once home with blackout blinds etc

27
Q

What can help adjust to new time zones?

A

Light levels and mealtimes.
Matching your first meal to the time zone you’ve arrived in.
Going to bed according to the new time

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