Biolgical Rhythms: Infradian And Ultradian Rhythms

Question 1

Infradian rhythms - menstrual cycle

Answer 1

• mentraul cycle is an example of an Infradian rhythm
• time between the first day of a woman’s period when the womb lining is shed to the day before her next cycle
• cycle is typically 28 days to complete.
• oestrogen (dev egg) and progesterone (womb lining thickness) are involved in the mentraul cycle

Question 2

Synchronising the menstrual cycle - study by McClintock

Answer 2

• is an endogenous system; but it may be affected by exogenous systems such as cycles of other women
• McClintock study; how mentraul cycle may synchronise as a result of pheromones;
  29 women, with history of irregular periods, samples of pheromones gathered from 9 women’s t different stages of their M.C, cotton placed in armpit
• pads from the start were applied to all 20 women
• found that 68% of women experienced changes to their cycle, brought them closer to the cycle of their donor

Question 3

What is Seasonal affective disorder ?

Answer 3

Depressive disorder which has seasonal pattern of onset, mental disorder

Question 4

Main symptoms of SAD

Answer 4

• Persistent low mood
• General lack of activity and interest in life
  Triggered in the winter months when the days are shorter

Question 5

What type of rhythm is SAD

Answer 5

• Infradian rhythm called circadian rhythm, yearly cycle
• can be a circadian rhythm, experience of SAD may be due to the disruption of the sleep wake cycle

Question 6

What hormone is associated with SAD

Answer 6

• hormone melatonin is implicated in the cause of SAD
• during the night he pineal gland secretes melatonin until dawn when there is an increase in light
• during the winter, lack of light in the morning means the secretion lasts longer
• has a knock on effect of serotonin release in the brain - linked to the onset of depressive symptoms

Question 7

Ultradian rhythms - sleep stages 1 and 2

Answer 7

Light sleep where a person may be easily woken
Stage 1 = brain waves have high frq, short amplitude - alpha waves
Stage 2 = alpha waves continue but there are occasional random changes in pattern called sleep spindles

Question 8

Stage 3 and 4 of the sleep cycle

Answer 8

• Deep sleep or slow wave sleep
• Brain waves are delta waves with lower frq, higher amplitude
• Difficult to wake someone at this point

Question 9

Stage 5 - REM sleep

Answer 9

• body is paralysed, brain activity resembles an awake brain
• brain produces theta waves and the eyes occasionally move around (rapid eye movement REM)
• dreams are experienced most during REM sleep

Question 10

Evaluate Infradian rhythms

Answer 10

Strength - menstrual synchrony may be explained by natural selection
- evolutionary value to have menstrual cycle and pregnancy at the same time
- babies who had lost their mothers to have access to milk. Increased chances of survival

Limitation - methodological shortcomings
- confounding variables e.g. stress, diet, exercise can influence the menstrual cycle
- therefore the studies are flawed

Question 11

Evaluate Ultradian rhythms

Answer 11

Strength - improved understanding of age-related changes in sleep
- slow wave sleep reduces with age; growth hormone is mostly produced during slow wave sleep, therefore is reduced in older people
- sleep deficit can explain issues in old age, like reduced alertness

Limitation - individual differences between people
- tucker et al large differences between pts in duration of each sleep stage cycle
- said they were likely biologically determined