Biological Rhythms

Question 1

What are circadian rhythms ?

Answer 1

Biological rhythms lasting 24 hours
For example the sleep/ wake cycle including hormones like melatonin.

Question 2

What provides primary input into the circadian rhythm?

Answer 2

Light - it acts as the external cue for sleeping or waking.

Question 3

How does the detection work ?

Answer 3

Light is detected by the eye , a message (concerning the brightness) is sent to the SCN.
The SCN uses the info to coordinate activity of the C system

Question 4

Research into Circadian Rhythms ?

Answer 4

Siffre
- Used himself as a case study. A French man spent 6 months in a cave without natural light or cues.
- When he woke up , he had artificial light to help him.
- His internal body was allowed to free fun and his cycle was 25-30 hrs.

Question 5

What did Siffre find , what’s this suggest ?

Answer 5

• Found that when he returned , he believed the date to be a month earlier than it was.
• Suggests the 24 hr cycle was increased by lack of external cues : believed one day = longer than it was and he thought fewer days had passed

Question 6

What else are sleep and wakefulness determined by ?

Answer 6

Homeostasis
- when someone has been awake a while, homeostasis tells the body there is need to sleep due to energy consumption.
- The homeostatic drive for sleep ^ during the day , reaching max in late evening.

Question 7

Another example of a circadian rhythm ?

Answer 7

Body temperature

Question 8

When is human body temp lowest and highest ?

Answer 8

• Human BT is at lowest in early hours and highest early evening

Question 9

When does sleep occur ?

Answer 9

• Sleep occurs when core temp drops , BT rises toward end of sleep cycle - promotes alertness 1st thing in morning

Question 10

A weakness of circadian rhythms ?
( differences )

Answer 10

P : Individual differences
E : Duffy found morning people rise early , go bed early whereas evening people wake and go to bed later.
L : Shows that there may be innate differences in circ. rhythms which suggests researchers should focus on differences during investigations

Question 11

Weakness of circadian rhythms (Temp)

Answer 11

P : There is suggestion that temp is more important than light in determining circ. rhythms.
E : Buhr found fluctuations in temp set the timing of cells in the body and caused tissues and organs to be active or inactive.
E : Body temp fluctuates on a 24hr rhythm - small changes can send a signal to body clocks.
L: Shows c rhythms are controlled and affected by diff factors - more holistic approach is necessary.

Question 12

Weakness of Siffre ‘s research
(Case study)

Answer 12

P: Case study , Siffre conducted multiple isolation studies but his results can not be generalised to the wider population - lack of ecological validity
- E.g even Siffre found that as he grew older, his pacemaker slowed which may have been an uncontrolled confounding variable in investigations
- limits the extent to which findings represent general population.

Question 13

External factors affect sleep wake cycles, what are they called?

Answer 13

Exogenous zeitgebers - for example daylight.

Question 14

What is an infradian rhythm ?

Answer 14

These are biological rhythms lasting longer than 24 hours and can be weekly, monthly or annually.

Question 15

Example of infradian rhythms ?

Answer 15

The menstrual cycle, regulated by hormones to promote ovulation.
Length can vary from 23-36 days.

Question 16

A second example of infradian rhythms?

Answer 16

SAD - seasonal affective disorder
- psychologists believe melatonin may be partially responsible.
- Lack of light in winter - longer period of melatonin secretion = linked to depressive symptoms

Question 17

Evaluation of infradian rhythms - reinberg

Answer 17

Examined woman who spent 3 months in a cave w only a small lamp to give light.
Her cycle decreased from 28 - 25.7 days. The exogeneous zeitgeber of light - affected the infradian rhythm

Question 18

Further evidence showing the effect of exogenous zeitgebers - Russell

Answer 18

• Sweat from one group of women to other group’s upper lip.
• Their cycles synchronised - suggesting synchronisation can be affected by pheromones.

Question 19

What does Russell’s research show ?

Answer 19

Shows that external factors must be taken into consideration when investigating infradian rhythms - more holistic approach rather than reductionist view that only endogenous factors cause influence.

Question 20

What is a strength of Russell’s experiment ?

Answer 20

• there is an evolutionary strength as if women synchronise periods, they can synch pregnancies meaning childcare can be shared among multiple mothers w kids at the same time.

Question 21

What is an ultradian rhythm ?

Answer 21

A biological rhythm lasting less than 24 hours and an example is the pattern of human sleep

Question 22

Describe the cycle of human sleep

Answer 22

Starts at light sleep - deep sleep - REM sleep, brain waves speed up, dreaming occurs and this repeats every 90 minutes

Question 23

Stages 1 and 2

Answer 23

Light sleep - brainwave patterns are slower, more rhythmic , starting with alpha and progressing to theta waves

Question 24

Stages 3 and 4

Answer 24

Deep sleep - slow wave sleep stages where it is hard to wake someone - associated with delta waves

Question 25

Stage 5

Answer 25

REM or dream sleep - body is paralysed and brain activity resembles someone who is awake

Question 26

Another ultradian rhythm example ?

Answer 26

Appetite/ meal patterns in humans - most eat 3 meals a day and appetite falls and rises due to food consumption

Question 27

A weakness of studying ultradian rhythms - ID

Answer 27

P: One weakness is individual differences
E: Tucker found differences in duration of each stage in Ps - particularly in stages 3 and 4
E: suggests innate differences in Ultradian rhythms
L: It is worth focusing on these differences when investigating sleep cycles

Question 28

Another weakness - research into ultradian rhythms

Answer 28

P : Tucker carried out experiment in a controlled lab setting
E: means differences could not be attributed to situational factors but only biological differences
E: The study provides support for the role of biological factors on ultradian rhythms, no situational factors were examined which play a factor

Question 29

Weakness of research into ultradian rhythms - Eco Val

Answer 29

P: Way in which research is conducted - tells us little about Ult. rhythms
E: When investigating sleep Ps must be subjected to a level of control.
E: may be invasive for the participant leading them to sleep in a way that doesnt represent their actual sleep cycle
L : This makes investigating rhythms hard due to lack of MR therefore false conclusions may be drawn.