Ovarian Cycle

Question 1

What is Spinnbarkeit?

Answer 1

Stretchiness of cervical mucus

Question 2

What is ferning?

Answer 2

In high oestrogen, just before ovulation, cervical mucus forms fern-like patterns due to crystallisation of NaCl on mucus fibres

Supports sperm penetration and increases ability to reach ovum

Question 3

Which two hypothalamic nuclei project to the portal plexus of the pituitary gland?

Answer 3

1. Medial pre-optic nucleus

2. Arcuate nucleus

Question 4

What controls GnRH secretion?

Answer 4

Feedback loops with gonadal hormones

Question 5

What type of feedback loop is seen in the male?

Answer 5

Only negative feedback

Question 6

What is the effect of testosterone on gonadotrophin output?

Answer 6

Depresses LH and FSH output

Question 7

What is the effect of inhibin on gonadotrophin output

Answer 7

Selectively depresses FSH output

No effect on LH

Question 8

What is the effect of slowly rising oestrogen in the female?

Answer 8

Negative feedback

Depresses LH and FSH output

Question 9

What is the effect of rapidly rising oestrogen?

Answer 9

Positive feedback

Stimulates LH and FSH output

Question 10

What is the effect of progesterone?

Answer 10

Depresses LH and FSH

1. Direct negative feedback
2. Inhibits positive feedback effect of oestrogen

Question 11

What controls LH and FSH secretion?

Answer 11

1. Output of GnRH
2. Sensitivity of pituitary to GnRH
3. Both

Question 12

Why is GnRH secretion pulsatile?

Answer 12

Continuous release would lead to adaptation and desensitisation

Question 13

Where is the site of negative feedback by oestrogen and progesterone in the brain?

Answer 13

Arcuate nucleus

Question 14

How does progesterone affect GnRH pulse?

Answer 14

Decreases pulse frequency

Question 15

How does oestrogen affect GnRH pulse?

Answer 15

1. Decreases pulse amplitude (in negative feedback)

2. Induces GnRH surge (in positive feedback)

Question 16

What causes the LH surge that triggers ovulation?

Answer 16

1. Gonadotropic cells of anterior pituitary hypersensitised due to inhibition of GnRH by negative feedback
2. Inhibition of anterior pituitary released due to rapidly rising oestrogen
3. GnRH surges due to hypothalamus stimulation by oestrogen
4. GnRH hyperstimulates hypersensitised anterior pituitary
5. Hypersecretion of LH

Question 17

What hormonal changes initiate puberty?

Answer 17

GnRH pulses

Question 18

What causes pubertal rise in GnRH?

Answer 18

Reaching body weight threshold

47kg for girls and 55kg for boys

Question 19

How body weight sensed?

Answer 19

Leptin receptors in hypothalamus

Gives indication of fat stores and therefore whether puberty should start

Question 20

What is menarche?

Answer 20

First period

Question 21

How do hormones affect behaviour?

Answer 21

1. Directly via action on brain

2. Indirectly via non-neural action

Question 22

What is the effect of testosterone on sexual behaviour in men?

Answer 22

1. Increases frequency of sexual thoughts
2. Increases frequency of sexual acts
3. Increases energy

Question 23

What is the effect of oestrogen in females on male activity?

Answer 23

Increased systemic oestrogen in females increases male’s sexual activity and acceptance of female’s invitations