Biological rythms

Question 1

What is a circadian rhythm

Answer 1

• a cyclical 24 hour long biological rhythm
• Sleep/wake cycle
• Core body temperature
• Affected by endogenous pacemakers and exogenous zeitgebers

Question 2

Research support for free running cicardian rythms

Answer 2

Siffre
- descended into a dark cave w no natural light
- Came put in September beleived it still to be August
- Siffre sleep- wake cycle didnt conform to 24 hour period it increased to 24hour and 30 minutes, even when all external cues about sleep/wake cycle were removed

Question 3

Evaluation of Circadian rhythms

Answer 3

Limitation - There are individual differences in Circadian rhythms. In particular teenagers. Professor of sleep medicine at Oxford altered start time of]f high school 8am to 10am. Overall better GCSE results. Adult and teen circadian rhythms don’t align, should be appreciated in order for better education

Strength- Research supporting free running body clocks. Siffre. 24.5. Natural circadian rythm despite lack of cues
HOWEVER
Uses case studies and small sample sizes - may not be generlisable, individual differences in duration and stages of cicardian rythm shown.
Case study cant be genelised, lacks scientific vigour
small sample size- hard to generlise

Question 4

Infardiun and Ultradiun rythms

Answer 4

Infradiun- Last longer than 24 hours. Menstrul cycle. Seasonal affective disorder (SAD)

Ultradiun- Last less 24 hour. Stages of sleep

Question 5

SAD and menstral cycle

Answer 5

SAD- an infradiun disorde caused by disruption to sleep wake cycle. Occurs in Winter. Longer nights means more melatonin secreted from pitutary glands. Changes in production of melatonin can lead to feelings of depression and lonliness

Menstral cycle- McClintok et al researched menstral synchronisation amongst 29 women irregular periods. Used Pheremones from 9 women from under armpits rubbed onto upper lip of 20 women. Ended up synching cycles.

Question 6

Ultradiun rythms and stages of sleep

Answer 6

stages 1 and 2 ‘sleep escalator’ can be easily awoken during thi stage
stages 3 and 4 delt waves much longer and slower
stage 5 REM sleep closely associated with dream and movement inhibition

Question 7

Evaluation Ultradiun and Infradiun

Answer 7

• Research support for stages of sleep. Dement and Kleitman. Studied 33 adults where alchol and caffeine was controlled. used EEG scans which monitored brainwave and showed distinct stages in the sleep cycle that repeated several times a night.
• Research for menstral sychnronisation - McClintok. rubbing pheremones on lips. However didnt control extranous variables like smoking, alchol consumption, weight which all may affect and individuals rythms. Raises dubts about influence of pheremones as an exongonous zeitgeber.

Dispute over basis of SAD
- compared Vitamin D treatment and phototheaphy
- Vitaminin D signif improvment
- Phototherapy none
- Phototherapy includes bright light exposure in order to induce melatonin secretion
- Suggests melatonin may have less signif impact on development of SAD

Question 8

What are the two ways our body remains the cycles

Answer 8

Endogonous pacemakers- Internal bodily regulators of biological rhythms entraining bio rythms to conform to cyclic periods

Exogonous zeitgebers- External enviromental changes affecting biological rythms to conform to cyclic periods

Question 9

How does the body manage the sleep/wake cycle

Answer 9

• The SCN part of hypothalamus receives info about light and dark from optic chiasm
• SCN passes this info to pineal gland which secretes melatonin
• When there is less light more melatonin produced less serotonin causing tiredness.
• When more light less melotnin produced more serotonin- more wakefullness

Question 10

Animal studies and the SCN

Answer 10

Influence of SCN demonstrated in animal studies
- Decoursey et al destroyed SCN connections in brains of 30 chipmunks who then returned to natural habitat observed after.
- Sleep/wake cycle of chipmunks by end of study had disappeared
- significant proportion of them had been killed by predators as were awake and vunerable to attack

• Ralph et al bred ‘mutant hamsters’ with 20 hour cycle.
• SCN cells frommutants transplanted into normal hamster
• cycles defaulted to 20 hours

Question 11

Examples of exogenous zeitgebers

Answer 11

1) Light in entraining the sleep wake cycle demonstarted by Siffre and Cambell and Murphy ( produced 3 hour sleep deviations by shining light onto back of their knees , light not always detected by eyes in order to entrain.

2) Social cues - These include set bedtime andmeal times signifiy when to sleep and wake. In order to avoid Jet lag accustom yourself to set sleeping eating time of destination to avoid desynchronisation of a pre-set cicardian rythm.