Biopsychology year 2 P2 //Biological rhythms Flashcards
what is meant by a circadian rhythm?
a cycle of activity that lasts for 24 hours for example the sleep wake cycle.
what is meant by a infradian rhythm?
a cycle of activity that lasts for more than 24 hours e.g. the menstrual cycle is 28 days.
what is meant by a ultradian rhythm?
a cycle of activity that lasts for less than 24 hours e.g. the sleep cycle is variations in brain activity that occurs over a 90 minute period several times in sleep.
what controls the sleep wake cycle and where is it located in the brain?
SCN - hypothalamus just above the optic nerves
what does our SCN do in the sleep wake cycle?
receives info about light from the eye, happens when our eyes are shut because light can penetrate through the eyelids, keeps us in rhythm with the outside world.
at night what does our SCN do in the sleep wake cycle?
level of light reduces so SCN sends signals to pineal gland instructing it to produce more melatonin which helps induce sleep. when sunrise comes melatonin is reduced .
what gene has been known to influence our sleep wake cycle?
PER3 - comes in different from and produces different circadian patterns - explains why peoples sleep patterns are different.
what evidence is there to support that SCN has importance in controlling our sleep wake cycle?
mutant hamsters specially produced to have a rhythm of 20 hours when cells from their SCN were transported to normal hamsters they had a shorter sleep wake cycle than 24 hours.
what practical application is there from research into the sleep wake cycle?
help people who need to go against their natural rhythm function. e.g. people who work night shifts need to be alert. research has produced more strategies e.g. working in very bright light and sleeping in total darkness - positive implications for economy - improved health and safety of shift workers.
explain the infradian rhythm the human menstrual cycle.
characterised by fluctuating hormone levels that regulate ovulation. Pituitary gland releases hormones which stimulates one ovary to ripen an egg - triggers the release of oestrogen. when egg is ripened progesterone is realised and prepares for pregnancy.
what external factors also effect the menstrual cycle?
pheromones - act on the person close by not the person producing them.
what supporting evidence is there for the role of external factors on the infradian rhythm the human menstrual cycle?
pheromones influencing the riming on menstrual cycle. collected sweat from under arm (sample of pheromones) and rubbed in on upper lip of other women, 68% of women experienced changes within their menstrual cycle.
what challenging evidence is there for the infradian rhythm the human menstrual cycle?
examined women basketball team and found no correlation between menstrual patterns. suggest external factors have less of an effect.
what is another example of a infradian rhythm?
seasonal affective disorder. - cycle of one year. brings out depressive symptoms during winter. triggered by melatonin - produced by pineal gland when dark to initiate sleep, in winter it is produced for long and surprises serotonin - low levels of serotonin = depression.
what practical application have we got from research into the second infradian rhythm SAD?
treatment to treat SAD - increases exposure to light to stop the production of melatonin through phototherapy - 60% effective.
