Repro 2.1

Question 1

From what embryological structure does the anterior pituitary gland form?

Answer 1

Rathke’s pouch

Question 2

What type of tissue is the anterior pituitary gland?

Answer 2

Endocrine gland

Question 3

What type of tissue is the posterior pituitary?

Answer 3

Nervous tissue

Question 4

What are trophic hormones?

Answer 4

Hormones which act on other endocrine tissues and promote the secretion of further hormones.

Question 5

What does the posterior pituitary secrete?

Answer 5

ADH and oxytocin

Question 6

What do the gonadotrophs secrete?

Answer 6

FSH

LH

Question 7

What do the corticotrophs secrete?

Answer 7

ACTH

Question 8

What do the somatotophs secrete?

Answer 8

Growth hormone

Question 9

What do lactotrophs secrete?

Answer 9

Prolactin

Question 10

How are the secretory cells in the anterior pituitary controlled?

Answer 10

Releasing hormones produced by nerve cells in the median eminence of the hypothalamus which pass to the anterior pituitary in the hypophyseal portal vessels

Question 11

Why are the hypophyseal portal vessels short?

Answer 11

Concentrated amount of releasing hormone from the hypothalamus to the anterior pituitary gland

Question 12

What releasing hormone controls the secretion of hormones from gonadotrophs?

Answer 12

Gonadotrophin Releasing Hormone (GnRH) controls the release of FSH and LH. GnRH is released in a pulsatile fashion causing pulsatile release of FSH and LH

Question 13

What do the gonadotrophins do?

Answer 13

Act on the gonads to influence the production of gametes and to promote the secretion of gonadal steroids - oestradiol and progesterone in females and testosterone in males.

Question 14

What controls the release of GnRH?

Answer 14

Gonadal steroids
Affected by their connection to other parts of the brain influenced by factors such as body weight and change in environment

Question 15

What effect does testosterone have on the secretion of GnRH?

Answer 15

Reduces GnRH secretion

Question 16

What effect does oestrogen have on GnRH?

Answer 16

At intermediate concentrations, oestrogen reduces the secretion of GnRH by reducing the amount secreted per pulse pressure (negative feedback)
At high concentrations without progesterone, oestrogen promotes the release of GnRH producing a ‘surge’ (positive feedback)

Question 17

What effect does progesterone have on GnRH secretions?

Answer 17

Progesterone increases the inhibitory effect of oestrogen by reducing the frequency of pulses
It can also inhibits the GnRH surge at high levels of oestrogen

Question 18

What influences the release of FSH and LH?

Answer 18

GnRH is required for the release of FSH and LH - without GnR, none would be secreted.
Oestrogen at directly effects their release, reducing the amount secreted at intermediate concentrations and at high concentrations promotes it
Inhibin also reduces the amount of FSH secreted in response to GnRH

Question 19

Where is inhibin produced?

Answer 19

a protein hormone produced by developing follicles in the ovary granulosa cells and seminiferous tubules sertoli cells in the testis

Question 20

What stimulates the secretion of testosterone?

Answer 20

LH - amount of testosterone secreted for level of LH is relatively constant

Question 21

How much testosterone does a man secrete each day?

Answer 21

4-10 mg

Question 22

What effect do the gonadotrophins have in the ovary during the astral phase of follicular development?

Answer 22

Cells of the theca interna bind LH
Granulosa cells bind FSH
LH stimulate thecal cells to produce androgens
FSH stimulates the granulosa cells to develop enzymes which convert the androgens to oestrogens

Question 23

What effect do the gonadotrophins have in the ovary during the pre-ovulatory phase of follicular development?

Answer 23

LH receptors develop in the outer layers of granulosa cells

A surge of LH will stimulate ovulation

Question 24

What effects do the gonadotrophins have on the corpus lute?

Answer 24

LH stimulates the corpus luteum to secrete progesterone and oestrogen
As the corpus luteum grows more steroids are produced at a given LH concentration

Question 25

Where does LH bind in the testes?

Answer 25

Leydig cells

Question 26

What enhances the effects of LH in the testes?

Answer 26

Prolactin and Inhibin

Question 27

What does testosterone do?

Answer 27

Acts on Sertoli cells to promote spermatogenesis and elsewhere in the body to maintain the reproductive system

Question 28

What effect does FSH have in the male reproductive system?

Answer 28

Maintains Sertoli cells and makes them responsive to testosterone

Question 29

Why must there constantly be appropriate levels of FSH and LH in the male?

Answer 29

They must produce sperm continually and be ever ready to deliver them to the female

Question 30

How are constant levels of FSH and LH maintained in the male?

Answer 30

Negative feedback of testosterone on GnRH secretion and it also reduces sensitivity of gonadotrophs to GnRH

Question 31

How is the rate of spermatogenesis controlled?

Answer 31

If it proceeds too rapidly inhibin levels rise and reduce secretion of FSH by acting on gonadotrophs

Question 32

What type of rhythm does testosterone follow?

Answer 32

Circadian rhythm - highest in the early morning

Question 33

What are the categories of the effects of gonadal steroids?

Answer 33

Determinative - qualitative and only partly reversible if at all. Mostly secondary sexual characteristics
Regulatory - highly reversible and rely on continuous hormonal stimulation for their maintenance

Question 34

What are the regulatory effects of testosterone?

Answer 34

Maintenance of the male internal genitalia
Metabolic effects - anabolic action
Behavioural effects - aggression and sexual activity