outline and evaluate circadian rhythms Flashcards
outline
Circadian rhythms are rhythms that occur once in a 24-hour period, e.g., the sleep wake cycle.
All biological rhythms are controlled by 2 factors: endogenous pacemakers (the body’s internal biological clocks) and exogenous zeitgebers (external changes in the environment e.g., light and social cues).
The SCN is found in the hypothalamus in both hemispheres and is a group a neurones which regulate the actions of the pineal gland which is responsive to light.
During darkness, the pineal gland converts the hormone serotonin into melatonin (a chemical that encourages sleep) and it is these changing levels of hormones that affect the rhythms of the body.
In a case study, Siffre spent 61 days and nights in an underground cave, which was deprived of natural daylight, but with access to adequate food and drink.
During his time in the cave, Siffre found his biological rhythm remained regular (e.g., he fell asleep & woke up on a regular basis) but the rhythm extended to just over 25 hours.
strength 1
A strength of research into circadian rhythms is that it has practical applications, which is when the principles of biological rhythms have been applied in a real-world setting.
This is because research suggests that disrupting our circadian rhythm on a regular basis has negative effects, such as reduced concentration around 6am, making accidents and mistakes more likely.
Therefore, due to this research, preventative measures (such as scheduled breaks and rest) have been implemented to reduce accidents from occurring.
limit
A weakness of research into circadian rhythms is that there are individual differences, where there is variability between different groups of participants, which most research into circadian rhythms does not account for.
For example, research has suggested that cycle length can vary between 13 and 65 hours.
Additional research suggests differences in cycle onset, which could explain why some people prefer to rise early and go to bed early (e.g., 6am and 9am) whereas others prefer to rise late and sleep late (10am and 1am).
This challenges the concept that circadian rhythms are the same in all of us, and therefore reduces the validity of pieces of research that doesn’t account for these differences.
strength 2
Additional supporting research evidence comes from Decoursey et al who destroyed the SCN connections in the brains of 30 chipmunks and then were returned to their natural habitat and observed for 80 days.
Their sleep/wake cycle disappeared, and many were killed by predators.
This suggests endogenous pacemakers such as the SCN are clearly important in regulating our biological rhythms, which aid our survival.
