Lecture 4.1: Hormonal Control of Reproduction

Question 1

Hypothalamic-Pituitary-Gonadal Axis: Males

Answer 1

Hypothalamus (GnRH)
Anterior Pituitary (FSH & LH)
Gonads/Testes (Inhibin, Testosterone)

Question 2

What cells in males does FSH affect? What do these produce?

Answer 2

Sertoli Cells produce Inhibin

Question 3

What cells in males does LH affect? What do these produce?

Answer 3

Leydig Cells produce Testosterone

Question 4

Hypothalamic-Pituitary-Gonadal Axis: Females

Answer 4

Hypothalamus (GnRH)
Anterior Pituitary (FSH & LH)
Gonads/Ovaries (Inhibin, Progesterone, Oestrogen)

Question 5

What cells in females does LH affect? What do these produce?

Answer 5

Theca Cells produce Androgens

Question 6

What cells in females does FSH affect? What do these produce?

Answer 6

Granulosa Cells produce Inhibin, Progesterone, Oestrogen

Question 7

What are the 2 parts of the Pituitary Gland?

Answer 7

• Anterior Pituitary
• Posterior Pituitary

Question 8

What is the composition of the Anterior Pituitary Gland?

Answer 8

• Arises from Rathke’s Pouch
• Not nervous tissue
• Endocrine gland
• Mostly ‘trophic’ hormones

Question 9

What is the composition of the Posterior Pituitary Gland?

Answer 9

• Nervous tissue
• Neurosecretory gland

Question 10

What does the Posterior Pituitary secrete? (2)

Answer 10

• ADH
• Oxytocin

Question 11

What is the importance of Oxytocin in reproduction? (4)

Answer 11

• Social interaction
• Orgasm
• Labour
• Lactation

Question 12

Glycoprotein Hormones ()

Answer 12

• Follicle stimulating hormone
• Luteinising hormone

Question 13

What Cells produce FSH and LH?

Answer 13

Gonadotrophic Cells of Anterior Pituitary

Question 14

Polypeptide Hormones

Answer 14

• Growth Hormone
• Prolactin

Question 15

What Cells produce GH?

Answer 15

Somatotrophs

Question 16

What Cells produce Prolactin?

Answer 16

Lactotrophs

Question 17

Anterior pituitary secretions are controlled by the….via….travelling in the …….?

Answer 17

• hypothalamus
• hormones
• hypophyseal portal circulation

Question 18

What Hypothalamic hormone controls reproductive
hormones? How often is it released?

Answer 18

• Gonadotrophin releasing hormone (GnRH)
• Release is pulsatile (about once an hour)

Question 19

What is Control of GnRH secretion influenced by?

Answer 19

• Other neurones
• KISS 1 neuron is a key player
• Environmental effects
• Body weight
• Influence KISS1 neurone or GnRH neurones directly
• ‘Feedback’ from gonadal hormones

Question 20

What male hormone reduces GnRH secretion?

Answer 20

Testosterone

Question 21

….. titres of oestrogen reduce GnRH secretion?

Answer 21

Moderate

Question 22

…..titres of oestrogen alone promote GnRH secretion?

Answer 22

High

Question 23

What hormone prevents positive feedback of high oestrogen?

Answer 23

Progesterone

Question 24

What is the difference between how oestrogen and progesterone reduce GnRH?

Answer 24

• Oestrogen reduces GnRH per pulse
• Progesterone frequency of pulses

Question 25

What hormone from the gonads inhibits FSH secretion selectively?

Answer 25

Inhibin

Question 26

What does FSH bind to in the Testis?

Answer 26

Sertoli Cells

Question 27

What effect does FSH have in the testis?

Answer 27

* Stimulates spermatogenesis * Focus on meiotic steps * Sertoli cells stimulated to produce Inhibin * Inhibin secretion is a marker of the rate of spermatogenesis

Question 28

Actions of Testosterone (6)

Answer 28

* Stimulates gamete production * Maintains epididymis and vas deferens * Maintains prostate, seminal vesicles, bulbo-urethral glands * Production of semen * Development and maintenance of external genitalia and secondary sexual characteristics * Sexual dimorphism throughout the body & behaviour

Question 29

Female Reproductive Cycle: ‘Follicular’ or ‘Proliferative’ Phase

Answer 29

* Previous cycle has been unsuccessful so starts again * Follicles grow in ovary * Uterus prepared for sperm transport & implantation of conceptus * Changes to facilitate sexual interactions

Question 30

Female Reproductive Cycle: Ovulation

Answer 30

* Brief period of fertility * Formation of corpus luteum

Question 31

Female Reproductive Cycle: ‘Luteal’ or ‘Secretory’ Phase

Answer 31

* Corpus luteum in ovary grows and secretes more steroids [(oestrogen (from granulosal luteal cells), progesterone (from thecal luteal cells)] * Changes in uterus in preparation for pregnancy * Starts to decrease in size after 7-10 days * Autophagy due to hypoxia/starvation * Lack of maintenance signals from embryo * CL dies after 14 days

Question 32

What do Oestrogens stimulate? (7)

Answer 32

* Fallopian tube function * Thickening of endometrium * Growth & motility of myometrium * Thin alkaline cervical mucus * Vaginal changes * Changes in skin, hair, metabolism * Calcium metabolism

Question 33

Progesterone Actions (7)

Answer 33

* Further thickening of endometrium into secretory form * Thickening of myometrium, but reduction of motility * Thick, acidic cervical mucus * Changes in mammary tissue * Increased body temperature * Metabolic changes * Electrolyte changes

Question 34

Changes in the Uterus in Menstrual Cycle: Early Proliferative

Answer 34

Glands sparse Straight

Question 35

Changes in the Uterus in Menstrual Cycle: Late Proliferative

Answer 35

Functionalis has doubled Glands now coiled

Question 36

Changes in the Uterus in Menstrual Cycle: Early Secretory

Answer 36

Endometrium maximum thickness Very pronounced coiled glands

Question 37

Changes in the Uterus in Menstrual Cycle: Late Secretory

Answer 37

Glands adopt characteristic “saw-tooth” appearance