infradian and ultraradian rhythms

- 'universal' present across all of that gender and culture 

- nature vs nurture is this purely biological behaviour or are there envirmomental influences 

- infradian rhythms take over period over 24 hours eg menstral cycle 

- circalnnual rhythms happen yearly eg hibernation pattens 

- ultradian rhythm takes place over 24 hours eg slow wave sleep pattens 

- circadian rhythms operate with in 24 hour period eg sleep wake cycle 

seasonal affective disorder (SAD) - A winter depression which affects millions of people every winter between september and April in particular december, january, febuary. it is a type of infradian rhythm known as circannual rhythm as it is subject to a yearly cycle. this is caused by biochemical imbalance this is thought to be melatonin in the hypothalamus due to the shortening of daylight hours and lack of sunlight in winter. This can be a seriously disabling illness preventing them from functioning normally without continuous medical treatment treatments for others it is milder condition.

symptoms - a desire to oversleep and diffculty staying awake but in some cases disturbed sleep and early morning waking feeling fatigue and inability to carry out normal routine - craving carbs and sweet foods results in weight gain - feelings of misery, guilt and loss of self-esteem, sometimes hopelessness and dispair and loss of feelings -

SAD symtoms usually reoccur each winter a diagnosis can be made after two winters with symtoms the symptoms ussally disapper in spring this can begin at any age but main is 18-30 it occurs throughout the northern and southern hemispheres rare those living in hotter climates where daylight is stronger 

seen as an example of infradian rhythm as it only occurs once every month this is characterised by change in hormone levels which regulate ovulation a typical cycle lasts for 28 days during the cycle rising levels of oestrogen cause the ovary to develop an egg and release it after ovulation proesterone helps the womb grow thicker, preparing for pregnacy if pregnacy doesnt occur then the egg is absorbed and the womb lining comes away. endogenous system (internal) t is effected by external factors why women can sync 

study 

McClintock 1998 womens menstral cycles may start to synchronise as a result of female pherones that sample were 29 womne with historuy of irregular periods samples of pheromones of 9 women at different stages in their menstral cycles were taken by putting pads in their armpits they were worn for around 8 hours of the day to ensure pheromones were picked up the pads were treated with alchohol then frozen to be rubbed on the upper lip of the other paticpants on day one pads applied to all 20 women and on day two as well found that 68% of women expericed changes to their cycle which brought them closer to their odour donor.

It may have been advantageous for our ancestor females to menstruate together and become pregnant around the same time, so offspring could be cared for collectively, increasing their chances of survival. 

However, Schank (2004) questions the validity of this perspective - too mant females cycling together within a social group would produce competition for highest quality males (lowering the fitness of any potential offspring). From this point of view, the avoidance of synchrony would appear to be the most adpative evolutionary strategy and therefore, the one that would be naturally selected.

much of the knowledge of the influence of pheromones on behaviour is derived from animal studies in animal selection is well documented for instance the fact that sea urchins release pheromones into the surrounding water so other urchins in the collony will eject their sex cells simultaneously in contrast evidence for the effects on human behaviour remains speculative and inconclusive we dont really know if they have any effect 

evaluation for McClintock study the findings seem impressive but with such a small sample of women it can not be claimed that they are significant also there are a number of uncontrolled extraneous variables such as stress, diet, exercise which could explain the changes in menstral cycle the relationship to the donor could be by chance (or a product of the fact that all the women experieced increased similarities in these factors during the study) this means that the study offers very weak support for the concept of pheromones as an influence upon the menstral cycle 

evidence supports the role of melatonin in SAD. Terman (1988) found that the rate of SAD is more common in Northern countries where the winter nights are longer. For example, Terman found that SAD affects roughly 10% of people living in New Hampshire (a northern part of the US) and only 2% of residents in southern Florida. These results suggest that SAD is in part affected by light (exogenous zeitgeber) that results in increased levels of melatonin.

the understanding of the role of darkness in SAD has led to effective therapies, such as phototherapy.

Phototherapy uses strong lights in the evening and/or early morning to change levels of melatonin and serotonin - sufferers reported that daily use of this relieves them of their symptoms (although some question if this is down to the placebo effect).

EASTMAN ET AL. found that a placebo condition of phototherapy was less effective, but 32% of participants did improve with the placebo alone.

Ultradian rhythms last fewer than 24 hours and can be found in the pattern of human sleep A complete sleep cycle goes through the five stages examples included REM (rapid eye movement) and NREM (non-rapid movement) sleep Research using EEG has highlighted distinct brain waves patterns during the different stages of sleep introduction of the EEG in the 1930s was crucial in helping us understand how sleep works Dement and Kleitman in the 1950s used this to show that there are many stages of sleep that we go through in the night 

This reserch has helped people that work nightshifts that may lead to higher cases of deppression so number of employers use daylight bulbs and these same bulbs have been used to help treat those that have SAD.

 This reserch has helped people that work nightshifts that may lead to higher cases of deppression so number of employers use daylight bulbs and these same bulbs have been used to help treat those that have SAD. Also this has helped reserch into jet lag this is becasue you are adding multiple sleep cycles or adding a sleep cycle understand the physical and physcologial so planes have adapted such a windows and beds.

 There are 5 sleep stages - the cycle goes for 90 minutes.

- Awake brain produces Beta Waves.

- NREM sleep: Stages 1 and 2 - Relaxed, easily woken, heart rate slows. Alpha and Theta Waves.

- NREM sleep: Stages 3 and 4 - Metabolic rate slows, growth hormone produced, tempreture drops. Delta Waves.

- REM sleep: Brain/eyes active, body paralysed (paradoxical sleep).