Reproduction and the Sex Steroid Axis

Question 1

What is the range in days for a normal menstual cycle?

Answer 1

21-35

Question 2

Usually ovulation occurs at around day __

Answer 2

Usually ovulation occurs at around day 14

Question 3

Which hormones stimulate follicle development?

Answer 3

FSH and LH

Question 4

In the menstrual cycle, why does oestrogen levels increase throughout the follicular phase?

Answer 4

FSH and LH stimulate granulosa cells surrounding the egg

The granulosa cells increase in size and secrete insulin

Question 5

The follicular phase begins when levels of which hormone are low?

Answer 5

Oestrogen

Question 6

What is the impact of rising oestrogen levels in the menstrual cycle?

Answer 6

Uterine lining thickens

Question 7

After ovulation, what does the empty follicle become and which hormone does it secrete?

Answer 7

Corpus luteum

Progesterone

Question 8

What causes ovulation?

Answer 8

LH surge

Question 9

What causes rupture of the follicle wall allowing for the release of the egg?

Answer 9

Proteolytic enzymes and prostaglandins

Question 10

Which two hormones remain fairly low in concentration throughout the follicular phase?

Answer 10

1. Oestrogen
2. Progesterone

Question 11

What triggers menstruation?

Answer 11

Lack of hCG

Corpus luteum breakdown and subsequent progesterone decrease

Question 12

Describe the HPO axis

Answer 12

1. Hypothalamus secretes GnRH
2. Pituitary secretes FSH/LH
3. Ovaries produce oestrodiol, activins and inhibins

Question 13

Which part of the hypothalamus produces GnRH?

Answer 13

Arcuate nucleus

Question 14

Which cells does LH act on in order to produce oestrogen?

Answer 14

Theca cells

Question 15

Which cells does FSH act on in order to produce oestrogen?

Answer 15

Granulosa cells

Question 16

Which variant of GnRH is responsible for reproductive function?

Answer 16

GnRH1

Question 17

What are the key functions of FSH?

Answer 17

1. Recruits dominant follicle
2. Granulosa cell growth
3. Activates aromatase activity

Question 18

What is inhibin and what does it do?

Answer 18

Local peptide in follicular fluid

Negative feedback on pituitary FSH secretion

Enhances local LH-induced androstenedione production

Question 19

What is activin and what does it do?

Answer 19

Local peptide found in follicular fluid

Stimulates FSH induced oestrogen production

Question 20

Into which two components are the testes organised cellularly?

Answer 20

1. Tubular components
2. Interstitial components

Question 21

What are the two tubular components of the testes?

Answer 21

1. Sertoli cells
2. Germ cells

Question 22

What are the two interstitial components of the testes?

Answer 22

1. Leydig cells
2. Capillaries

Question 23

Which cells support germ cells within the testes in their development?

Answer 23

Sertoli cells

Question 24

Which hormone acts on

a) Sertoli cells
b) Germ cells

Answer 24

a) FSH
b) LH

Question 25

How long does spermatogenesis take?

Answer 25

Roughly 90 days

Question 26

Which two hormones stimulate spermatogenesis?

Answer 26

FSH and testosterone | (LH stimulates testosterone production)

Question 27

For which reasons is an oocyte much larger than a sperm cells?

Answer 27

1. Yolk proteins 2. Ribosomes 3. t-RNA 4. m-RNA 5. Protective chemicals

Question 28

Where does fertilisation occur?

Answer 28

Ampullary region of the Fallopian tubes

Question 29

What is capacitation?

Answer 29

The functional maturation of a spermatozoon (mature sperm)

Question 30

Where does capacitation occur?

Answer 30

Female reproductive tract

Question 31

What is the zona pelludica?

Answer 31

A glycoprotein layer surrounding the plasma membrane of the oocyte

Question 32

The acrosomal reaction of the sperm is triggered by what?

Answer 32

Binding to ZP3 (zona pelludica 3)

Question 33

How is polyspermy prevented?

Answer 33

1. Na⁺ influx in response to sperm binding (fast block) 2. Ca₂⁺ release in an indirect response to sperm binding (slow block)

Question 34

As well as egg activation, which 3 other effects does the sperm have during fertilisation?

Answer 34

1. Triggers the egg to complete meiosis 2. Triggers a cytoplasmic rearrangement 3. Causes a sharp increase in protein synthesis and metabolic activity in general

Question 35

What does the final stage of fertilisation involve?

Answer 35

Fusion of nuclei to form a zygote