Circadian rhythms : biopych

what is a circadian rhythm

internal cycles that last around 24 hours, eg sleep/wake cycle

what are our circadian rhythms influenced by

endongeneuos pacemakers (our internal body clock) , exogenous zeitgerbers (external factors effecting cycles)

what is the main endegenous pacemaker

the SCN , a bundle of nerves

where is the SCN located

in the hippothalmus in the brain , above the optic area(eyes)

Why is where the SCN important

it means it recieves info about light directly and can pass that info to the pineal gland

what does the pineal gland do

releases melotonin which induces sleepiness

therefore how does this process effect our circadian rhythms

the more light , the less melotonin the pineal gland releases

How then do our circadian rhythms work when we don't have access to any light

the SCN generates a rhythm related to the production of proteins, when at a certain level of protein , the pineal gland releases melotonin

What is an exogeneuous zeitgerber

external cues that effect our circadian rhythms

how are exogeneuous zeitgerbers important

governs the exogeneos pacemakers

Supporting research is

Siffre's cave study

What did Siffre do

spent two months living in a cave with no natural light and no clocks. Meaning the only influence was his internal body clock

What were some of Siffres findings

When he was released he had believed it to be a month earlier than it was, the lack of external cues had made him feel the day was longer

What did Siffre conclude from this

That when we have a lack of exogeneus zeitgerbers our natural body clock changes to 25 hours. This means that

Weakness of research into circadian rhythms

Small sample sizes, meaning it is difficult to make meaningful generalisations

An issue with the reasearch

Confounding variables, in theses studies they still has access to artifical light, which czeisler suggested that artifical light does have an influence on circadian rhythms.

A strength of research into circadian rhythms

Practical application, providing a better understanding for night workers ect

Research supporting exogeniours pacemakers

Ralphs hamster study

What did the hamster study do

hamsters bred to have a circadian rhythm of 20 hours , they transplanted these abnormal cells into normal hamsters

what did ralph find

that these hamsters adopted the same rhythm of 20 hours, showing the significance of the SCN on rhyhtms

Research supporting exogeneuos zeitgerbers

Campbell and murphy, showing light may be detected by skin

What was campbell and murphys study

15 participants woken up at random times and a light pad was shone on their knees, their sleep/wake cycle changed up to 3 hours in some cases

what does campbell and murphys research suggest

that exogenous zeitgerber (light) is so powerful that doesn't need to rely on eyes to work