Infradian Biological Rhythms

Question 1

Give an example of an Infradian Rhythm and explain why

Answer 1

Female menstrual cycle, regulated by monthly changes

one cycle lasting around 28 days

Question 2

How many phases are in a single menstrual cycle and what are they largely controlled by?

Answer 2

4 key phases

endogenous pacemakers such as hormones

Question 3

(Menstrual phase) As the lining of the uterus is shed, what does the hypothalamus stimulate?

Answer 3

The pituitary gland which releases follicle stimulating hormone.

Question 4

(Follicular phase) what increases as the follicles in the ovary mature to ripen an egg?

Answer 4

Oestrogen levels

Question 5

What happens as a consequence of increased FSH and Leutinising Hormone (LH) in the Ovulation phase?

Answer 5

An egg is released into the uterus

Question 6

In the Lutial stage, what causes the uterus lining to be thickened for pregnancy and what happens if that does not occur?

Answer 6

Increased levels of progestrogen

LH, FSH and progestrogen decrease.

Question 7

What evidence from Mc Clintock is there to suggest the influence of exogenous factors on the menstrual cycle?

Answer 7

29 iregular cycle females collected pheromones

rubbed on lips of other females

68% had changes to their cycle similar to their donor’s

Question 8

Female’s pheromones act as..?

Answer 8

exogenous zeitgebers that influence the control of the cycle

Question 9

What confounding variables can affect the menstrual cycle?

Answer 9

severe stress and malnutrition

Question 10

It is likely that infrafian rhythms are controlled by a combination of endogenous and exogenous factors because?

Answer 10

Patterns of synchronisation could be due to due to those factors and can be expected to occur by chance