Infradian and Ultradian rhythms

Question 1

What is an infradian rhythm?

Answer 1

• A type of biological rhythm with the frequency of less than one cycle in 24 hours such as menustruation and seasonal affective disorder

Question 2

What is an ultradian rhythm?

Answer 2

• A type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep

Question 3

Describe the endogenous system of the menstrual cycle

Answer 3

• The menstrual cycle is governed by changes in hormone levels which regulate ovulation.
• The cycle begins on the first day of their period to the day before her next
• During each cycle, oestrogen causes the ovary to develop an egg and release it
• After ovulation, the hormine progesterone helps the womb grow thicker, readying the womb for pregnancy
• If this doesnt occur, the egg is absorbed and the womb lining comes away and leaves the body

Question 4

What is an exogeneous factor on the menstrual cycle

Answer 4

• phermones which are chemical signals that organisms release to communicate with other members of their species. They are released through sweat,urine and feces and are detected by smell
• humans are absorbed by being in close proximity and are thought to synchronise period cycles

Question 5

What research was done on phermones?

Answer 5

• Stern and McClintock did research on the effect of phermones on the menstrual cycle
  Aim = they wanted to see if phermones had an effect on menstrual cycles
  Procedures = they gathered 29 participants with a history of irregualr periods
• they then gathered phermone samples from 9 of these women at different stages of their menustrual cycle via a cotton pad in their armpit for 8 hours
• the cotton pads were then treated with alcohol and freezed
• They then rubbed these on the lips of participants
• On day one pads from the start of the menstrual cycle were given and so on
  Findings = 68% of participants expierenced changes that brought them closer to cycle of the ‘odour donor’
  -

Question 6

What is seasonal affective disorder?

Answer 6

• A depressive disorder diagnosed by DSM - 5
• it is characterised by low mood, low activity and low interest in life
• this is known as a circannual rhythm ( a type of infradian) as it occurs at a yearly cycle

Question 7

What is the role of endogeneous and exogeneous factors in SAD?

Answer 7

(endogeneous) melatonin is a hormone that due to extended periods of darkness (exogeneous) is secreted for longer periods of time. This interferes with the secretion of serotonin and decreases it causing the onset of depression

Question 8

What are two strengths of research into infradian rhythms?

Answer 8

1. A strength is that we can understand the evolutionary basis if menstrual synchrony. Synchronisation can be linked to our distant ancestors who may have thought it was advantageous for women to menstruate together and become pregnant at the same time. This would allow babies who have lost their mothers to have access to breast milk, showing it is an adaptive strategy
2. Another strength is that there are real world applications such as light therapy to treat SAD. This stimulates a reset of the bodies internal clock and has reduced the effects of SAD in 80% of people.
   - It is also preferred over antidepressants as it is considered safe.
   - however light therapy has high relapse rates in 46% and side effects

Question 9

What is a limitation of infradian rhythms?

Answer 9

• Stern and McClintock may have had confounding variables in their research such as diet, stress and exercise which means there may not be cause and effet
• This may explain ehy his research has not been effectively replicated

Question 10

How long does each stage of sleep last and how many stages are there?

Answer 10

• Each stage in a cycle lasts 90 minutes
• There are 5 stages

Question 11

What occurs in stages 1 and 2?

Answer 11

• this is light sleep where a person may be easily woken. In stage 1, brain waves are high frequency and have a short amplitude. These are alpha waves

Question 12

What occurs in stages 3 and 4?

Answer 12

• this is deep sleep or slow wave sleep. Brain waves are delta waves with lower frequency and higher amplitude. It is difficult to wake someone at this point

Question 13

What occurs during stage 5

Answer 13

• The body is paralysed yet brain activity resembles an awake brain
• the brain has theta waves and our eyes occassionally move
• dreams are most often expierenced during REM sleep but may occur in deep sleep

Question 14

What is a strength of ultradian rhythms?

Answer 14

• one strength is that it provides an improved understand age related changes in sleep
• some scientists have observed that SWS reduces with age and have explained this as growth hormone is mostly produced in SWS, therefore in old age it is reduced
• ## A lack of SWS in older ages may cause lack of alertness. In order to increase SWS, relaxation and medication is used

Question 15

What are two limitations of Ultradian rhythms research?

Answer 15

• There are individual differences between the duration pf each sleep stage specifically 3 and 4
• Tucker said these differences are likely to be biological
• There are also also extraneous variables in research to sleep stages for example they occur in lab settings so noise and temp may affect sleep