Biological Rhythms: Infradian Rhythms

Question 1

what are infradian rhythms?

Answer 1

• a cycle that takes longer than 24 hours to complete
• can be a month or year or seasonal

Question 2

what is an example of a infradian rhythm?

Answer 2

menstrual cycle

Question 3

what is the menstrual cycle?

Answer 3

it is governed by monthly changes in the hormone levels which regulate ovulation

Question 4

what type of system is the menstrual cycle?

Answer 4

endogenous system but can be affected by exogenous factors

Question 5

how long does the menstrual cycle last?

Answer 5

• first day of a women’s period to the day before her next period
• approximately 28 days (24-35 days)

Question 6

what happens during each cycle?

Answer 6

• rising levels of the hormones oestrogen causes the ovary to develop an egg and release it (ovulation)

Question 7

what happens after ovulation?

Answer 7

• hormone progesterone helps the womb lining to grow thicker, readying the womb for pregnancy
• if pregnancy does not occur, the egg is absorbed into the body, the womb lining comes away and leaves the body (menstrual flow)

Question 8

what can the menstrual cycle be influenced by even though it is an endogenous system?

Answer 8

exogenous factors, such as cycles other women

Question 9

who are the researchers involved with demonstrating synchronisation of menstrual cycles?

Answer 9

Stern and McClintock

Question 10

what are pheromones?

Answer 10

chemical signals that organisms release to communicate with other members of their species

Question 11

how are pheromones often released and detected?

Answer 11

• sweat
• urine
• faeces

and are detected through smell

Question 12

what was the aim of Stern and McClintock?

Answer 12

• see if the menstrual cycle can be synchronised by the influence of female pheromones

Question 13

what was the procedure of Stern and McClintock?

Answer 13

• 29 women with a history of irregular periods
• pheromone samples were gathered from 9 of these women at different stage of the menstrual cycle via a cotton pad place in their armpit, this was worn for 8 hours to pick up the pheromones
• the pads were frozen and treated with alcohol to be rubbed on the upper lip of the other ppts

Question 14

what were the results of Stern and McClintock?

Answer 14

• on day one, pads from the start of the menstrual cycle were given to each women and on day 2 pads from the second day of the cycle and so on
• 68% of women experienced changes to their cycle which brought them closer to the cycle of the odour donor

Question 15

what is SAD?

Answer 15

• seasonal affective disorder
• depressive disorder which has a seasonal pattern of onset, described and diagnosed as a mental disorder in the DSM-5

Question 16

what are the main symptoms of SAD?

Answer 16

• persistent low mood
• lack of activity
• low interest in life

Question 17

what is SAD often referred to as and why?

Answer 17

winter blues as the symptoms are triggered by the winter months when the day gets shorter

Question 18

what are the roles of endogenous and exogenous factors in SAD?

Answer 18

• melatonin is a hormone that is implicated in the cause of SAD, it is produced in the evening until dawn when there is an increase in light by the pineal gland, but in winter there is a lack of light in the morning so this secretion process continues for longer
• this has a knock on effect on the production of serotonin in the brain = a chemical that has been linked to the onset of depressive symptoms

Question 19

what are the evaluation points for infradian rhythms?

Answer 19

+ evolutionary basis
- methodological limitations
+ real-world applications