Biological Rhythms

Question 1

What is a biological rhythm?

Answer 1

A series of repetitive biological processes regulated by your internal clock.

Question 2

What are biological rhythms regulated by?

Answer 2

-Endogenous pacemakers.
-Exogenous zeitgebers.

Question 3

What is the main example of an endogenous pacemaker?

Answer 3

-SCN.

Question 4

What are examples of an exogenous zeitgeber?

Answer 4

-Light.
-Social cues (e.g. meal times).

Question 5

What are endogenous pacemakers?

Answer 5

The body’s internal body clocks that regulate biological rhythms.

Question 6

What are exogenous zeitgebers?

Answer 6

External environmental cues that reset our biological clocks.

Question 7

Can endogenous pacemakers be affected by the environment?

Answer 7

Yes.

Question 8

What do external cues do to biological rhythms?

Answer 8

External cues entrain biological rhythms.

Question 9

What is a free running cycle?

Answer 9

Where one’s daily sleep cycle does not depend on external cues.

Question 10

Where is the SCN?

Answer 10

The hypothalamus.

Question 11

What is the SCN linked with?

Answer 11

The pineal gland.

Question 12

How does the sleep/wake cycle work?

Answer 12

1. The SCN (E.P.) receives information about light levels (E.Z.) from the optic nerve.
2. This sets the circadian rhythm so that it is in synchronisation with the outside world (e.g. day and night).
3. The SCN sends signals to the pineal gland (E.P.)
4. This leads to an increase in the production of melatonin (sleep hormone) at night, helping to induce sleep.

Question 13

If there is a lack of natural light, what exogenous zeitgebar can substitute for it?

Answer 13

Social cues (e.g. meal time).

Question 14

What are circadian rhythms?

Answer 14

Any cycle that lasts 24 hours.

Question 15

What is an example of a circadian rhythm?

Answer 15

The sleep/wake cycle.

Question 16

What does circadian mean in Latin?

Answer 16

About day.

Question 17

Why are circadian rhythms important?

Answer 17

It optimises an organism’s physiology and behaviour to meet the varying demands of the day/night cycle.

Question 18

What is the purpose of circadian rhythms?

Answer 18

Regulating behaviour and body states in response to environmental changes.

Question 19

How did Folkard (1985) research circadian rhythms?

Answer 19

Folkard placed 12 participants in a cave for three weeks with no E.Z., subtly giving them 22 hour time cues (e.g. by speeding up the clock).

Only 1 out of 12 participants couldn’t adjust to the shortened day.

This suggests the flexibility of the circadian system and how it differs between individuals.

Question 20

How did Siffre (1962) research circadian rhythms?

Answer 20

Siffre (1962)
Siffre tested his internal body clock (E.P.) by spending 61 days & nights in a cave with no E.Z. He settled into a 25-30 hour sleep/wake cycle.
This supports the assumption that endogenous pacemakers exert an influence on circadian rhythms, while showing the strength of circadian rhythms as a free running cycle.

Question 21

What is a limitation of Siffre’s (1962) circadian rhythm study?

Answer 21

He used artificial light (headlight), which could act as an E.Z.

Question 22

What are infradian rhythms?

Answer 22

A cycle that lasts longer than 24 hours (e.g. weekly, monthly, annually).

Question 23

What are examples of infradian rhythms?

Answer 23

-Female menstrual cycle.
-Season affective disorder (SAD).

Question 24

Features of the female menstrual cycle (infradian rhythms):

Answer 24

-24-35 days long.
-Ovulation (egg release) occurs.
-The thickening womb lining sheds if there is no pregnancy.

Question 25

Features of seasonal affective disorder (SAD) (infradian rhythms):

Answer 25

Lack of light in winter months results in a longer period of melatonin secretion, which is linked to depressive symptoms.

Question 26

How did McClintock (1998) study infradian rhythms?

Answer 26

McClintock conducted a longitudinal field study where the menstrual cycles of women became synchronised after being exposed to a ‘donor’ pheromone (E.Z.).

Question 27

What are ultradian rhythms?

Answer 27

Any cycle that lasts less than 24 hours.

Question 28

What is an example of ultradian rhythms?

Answer 28

The stages of the sleep/wake cycle.

Question 29

How many stages of the sleep/wake cycle are there?

Answer 29

5.

Question 30

How long does each stage of the sleep/wake cycle last?

Answer 30

90 minutes.

Question 31

Stages 1 & 2 of the ultradian cycle:

Answer 31

‘Light sleep’ stages.
One can be easily woken up.
Slower alpha wave brain patterns start to form, becoming even slower in the form of theta waves as sleep becomes deeper.

Question 32

Stages 3 & 4 of the ultradian cycle:

Answer 32

‘Deep sleep’ stages.
It will be more difficult to wake someone up.
Involves delta waves.

Question 33

Stage 5 of the ultradian cycle:

Answer 33

‘REM (rapid eye movement) sleep’ stage.
The body is paralysed while brain activity speeds up.
Highly correlated with people dreaming.

Question 34

How did Dement & Kleitman (1967) study ultradian rhythms?

Answer 34

Dement & Kleitman (1967) measured brain activity on 9 participants using EEG. When waking people up during the REM stage, people would recall what they had dreamt about clearly.