BIOLOGY UNIT 2 K2

Hormonal control of reproduction

What is a hormone ?

A hormone is a chemical that is produced at one site but has an effect at another site

What do hormones produced in the pituitary glands and the hypothalamus control ?

Hormones produced in the pituitary glands and the hypothalamus control the onset of puberty, sperm production and the menstrual cycle

What hormone is produced during puberty ?

At puberty, the hypothalamus produced a releaser hormone whose target is the pituitary gland

What 2 hormones is the pituitary gland stimulated to produce ?

The pituitary gland is stimulated to produce 2 hormones :

1. FSH this is the follicle stimulating hormone and is present in males and females

2. ICSH is the interstitial cell stimulating hormone and is present in males and LH is the luteinising hormone that is present in females

What does the release of FSH, ICSH and LH trigger ?

The release of FSH,ICSH and LH triggers the onset sperm production in men and the menstrual cycle in women

What are FSH and ICSH produced by and where do they travel ?

FSH and ICSH are produced by the pituitary gland and they travel in the bloodstream to the testes

What does FSH do in the sperm production

FSH promotes sperm production in the seminiferous tubules

What does ICSH do in sperm production

ICSH stimulates the interstitial cells to produce the hormone testosterone

What is the role of testosterone 

• stimulates sperm production in the seminiferous tubules and activates the prostate gland and seminal vesicles to produce their secretions 

Name 1,2,3,4,5,6,7,8,9,10 and 11

1. hypothalamus

2. releaser hormone

3. pituitary

4. FSH

5. ICSH

6. testes

7. sperm

8. interstitial

9. testosterone

10. sperm

11. secretions

How is the concentration of testosterone in the blood prevented from becoming too high ?

As the concentration of testosterone builds up in the bloodstream, it reaches a level where it inhibits the secretion of FSH and ICSH by the pituitary gland which then leads to a decrease in testosterone production, this is called negative feedback control

At the start of puberty what is the part of the brain that produces the releaser hormone ?

The hypothalamus is the part of the brain that produces the releaser hormone at the start of puberty 

What are the stages of the menstrual cycle called ?

• The Follicular Phase

• The Luteal Phase

How long does the menstrual cycle take and what ice the first day called ?

The menstrual cycle takes approximately 28 days and the first day of menstruation is regarded as day one of the cycle

What hormones are produced during the follicular phase and what are they produced by ?

• FSH (produced by the pituitary gland)

• Oestrogen (produced by follicle in ovary)

• LH (produced by pituitary gland)

What does the hormone FSH do in the follicular phase of the menstrual cycle ?

FSH (produced by the pituitary gland) stimulates development and maturation of a follicle and stimulates production of the hormone oestrogen by the follicle 

What does the hormone Oestrogen do in the follicular phase of the menstrual cycle ?

Oestrogen (produced by follicle in ovary) stimulates the proliferation of the endometrium, preparing it for implantation. Peak levels of oestrogen stimulate a surge in the secretion of LH. Oestrogen affects the consistency of cervical mucus making it more easily penetrated by sperm

What does the hormone LH do in the follicular phase of the menstrual cycle ?

A surge of LH (produced by pituitary gland) triggers ovulation

What is ovulation and when does it occur ?

Ovulation is the release of an egg from a follicle in the ovary and it usually occurs around the midpoint (day14) of the menstrual cycle.

What hormones are produced during the luteal phase and what are they produced by ?

• LH (produced by pituitary gland)

• Progesterone (produced by corpus luteum) 

What does the hormone LH do in the follicular phase of the menstrual phase ?

LH (produced by the pituitary gland) stimulates the follicle to develop into the corpus luteum and the corpus luteum starts to secrete progesterone

What does the hormone progesterone do in the luteal phase of the menstrual cycle ?

Progesterone promotes further development and increases vascularisation of the endometrium, preparing it for implantation if fertilisation occurs

Name 1,2,3,4,5,6,7,8,9,10,11 and 12

1. hypthalomus 

2. releaser hormone

3. pituitary

4. FSH

5. LH

6. ovaries

7. FSH

8. oestrogen

9. LH

10. ovulation

11. corpus luteum

12. progesterone 

What happens to the corpus luteum if fertilisation does not occur ?

If fertilisation does not occur (lack of LH) this leads to the degeneration of the corpus luteum and therefore a decrease in progesterone eves leading to menstruation

If fertilisation does occur what happens to the corpus luteum ?

If fertilisation does occur the corpus luteum does not degenerate and progesterone levels remain high

What do high levels of oestrogen and progesterone cause ?

High levels of oestrogen and progesterone levels inhibit the secretion of FSH and LH by the pituitary gland. Concentrations of FSH and LH decrease preventing new follicles from development 

High levels of oestrogen and progesterone inhibit secretion of which hormones ?

High oestrogen and progesterone levels inhibit secretion of FSH and LH

What does this follicle develop into following ovulation ?

After ovulation the follicle develops onto the corpus luteum

Describe the role of oestrogen in triggering ovulation

Peak levels of oestrogen stimulate a surge in the secretion of LH which then triggers ovulation