(7) INFRADIAN RHYTHMS

Question 1

What are the two infradian rhythms are we looking at

Answer 1

Menstrual cycle and seasonal affective disorder

Question 2

Definition of endogenous and exogenous and Infradian cycle

Answer 2

Endogenous - internal body factors
Exogenous - external environmental factors
Infradian cycle - over 24 hours

Question 3

How long is the menstrual cycle and when does the bleeding happen

Answer 3

28 days (21-35)
Bleeding happens on the 1st

Question 4

The cycle:

Answer 4

□ Oestrogen
® Levels increase, the ovary develops and releases an egg
□ Progesterone
® After ovulation
® Helps uterus lining grow thicker
® Readies body for pregnancy
□ If pregnancy occurs:
® Egg absorbed into body, womb lining leaves body
◊ Via blood
◊ This is menstrual flow

Question 5

What does research on the menstrual cycle suggest?

Answer 5

□ Menstrual cycle is an endogenous system
□ Research shows can be influenced by exogenous factors

Question 6

How was research on the menstrual cycle carried out?

Answer 6

® McClintok
◊ 29 women with irregular periods
◊ Sample of pheromones (from 9/29) women at different stages of cycle rubbed on upper lip of other participants

Question 7

What were the findings of McClintok’s menstrual cycle research and what do they suggest

+ criticisms

Answer 7

® Findings:
◊ 68% women experienced change to cycle
} Brought them closer to cycle of odour donor
□ So?
® Menstrual cycle could be influenced by exogenous factors

			□ Criticism:
				® Small sample
				® Uncontrolled extraneous variables
					◊ Eg stress, diet exercise

Question 8

What is the a03 of the menstrual cycle

Answer 8

□ Evolutionary explanation:
® What?
◊ Menstrual synchrony
} Birth happens at same time
– So everyone can collectively care for newborns
® However:
◊ Unfalsifiable
} Cannot scientifically prove this claim

Question 9

What is SAD and what are its main symptoms

Answer 9

○ What is it?
§ Depressive disorder with seasonal pattern
○ Main symptoms:
§ Persistent low mood
§ Lack of activity
§ Lack of interest

Question 10

When does SAD usually take place and why?

Answer 10

○ When?
§ During winter months
□ September-feb
□ Daylight hours = shorter
○ Why?
§ Melatonin
□ When dark, pineal gland secretes melatonin
□ More dark in winter months so more melatonin
□ More melatonin = less serotonin
® Lack of serotonin = depressive symptoms

Question 11

What is the a03 of SAD

Answer 11

Practical application:
• What?
○ Phototherapy
§ Stimulates very strong light in morning and evening
§ Resets melatonin levels
§ Relieves 60% of sufferers
• So?
○ Understanding the role of melatonin helps produce therapies to sufferers