Key Area 2- Hormonal Control of Reproduction

Question 1

What is a hormone?

Answer 1

A chemical that is produced at one site, and has an effect on another site.

Question 2

What are hormones produced by?

Answer 2

Endocrine glands. (They are secreted directly into the blood stream)

Question 3

What happens when a hormone reaches its target tissue?

Answer 3

It brings about a specific effect.

Question 4

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

Answer 4

The onset of puberty, sperm production and the menstrual cycle.

Question 5

What does the hypothalamus secrete at puberty?

Answer 5

A releaser hormone whose target is the pituitary gland.

Question 6

What hormones is the pituitary gland stimulated to release?

Answer 6

FSH (follicle-stimulating hormone, in males and females), and ICSH (interstitial cell-stimulating hormone, in males) or LH (luteinising hormone, in females0

Question 7

What does the release of these hormones trigger?

Answer 7

The onset of puberty, for example sperm producion and the menstrual cycle.

Question 8

What happens when FSH arrives in the bloodstream at the testes? (EFFECT)

Answer 8

It promotes sperm production in the seminiferous tubules.

Question 9

What happens when ICSH arrives in the bloodstream at the testes? (EFFECT)

Answer 9

It stimulates the interstitial cells to produce the male sex hormone testosterone.

Question 10

What does testosterone stimulate and activate?

Answer 10

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

Question 11

Describe the negative feedback control of testosterone production by FSH and ICSH.

Answer 11

• 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
• This leads to a decrease in testosterone concentration, which then triggers the pituitary gland to again make FSH and ICSH
• And so on…

Question 12

Where is FSH and ICSH released from?

Answer 12

The pituitary gland

Question 13

Where is testosterone released from?

Answer 13

Interstitial cells

Question 14

What is the target of FSH?

Answer 14

Seminiferous tubules

Question 15

What is the target of ICSH?

Answer 15

Interstitial cells

Question 16

What is the targets of Testosterone?

Answer 16

Seminiferous tubules, prostate gland & seminal vesicles and the pituitary gland

Question 17

What are the effects of Testosterone?

Answer 17

Sperm production, produce secretions and negative feedback of FSH and ICSH

Question 18

What are the Two stages of the menstrual cycle?

Answer 18

The Follicular phase and the Luteal phase

Question 19

What does FSH (secreted from pituitary gland) stimulate when it reaches the ovary?

Answer 19

• The development and maturation of a follicle
• The production of oestrogen by the follicle

Question 20

What happens when the ovary wall secretes oestrogen?

Answer 20

• It stimulates proliferation (cell division) of the endometrium (inner layer of the uterus) following menstruation, preparing it for implantation
• Affects the consistency of cervical mucus making it more easily penetrates by sperm

Question 21

What do high concentrations of oestrogen trigger?

Answer 21

The production of LH and FAH by the pituitary gland at approximately ‘day 14’

Question 22

What does the surge of LH cause?

Answer 22

.It directly causes ovulation by causing the follicle to rupture and release the ovum
.The ovum then moves along the oviduct, and over this very short period of 2-3 days, fertilisation may occur if the ovum meets a sperm

Question 23

What is ovulation?

Answer 23

.It is the release of an egg (ovum) from a follicle in the ovary. It usually occurs around the mid-point of the menstrual cycle

Question 24

What happens during the luteal phase?

Answer 24

.LH stimulates the follicle to develop into the corpus luteum
.The corpus luteum secretes progesterone
.The rise in progesterone concentration stimulates further development and vascularisation of the endometrium so it becomes thick, spongy and has an increase in vascular blood vessels, preparing it for implantation if fertilisation occurs
.High levels of oestrogen and progesterone trigger an inhibitory effect on the pituitary gland, so concentrations of FSH and LH drop as a result preventing further follicles from developing at this time. This is an example of negative feedback control

Question 25

What happens if fertilisation doesn’t occur?

Answer 25

.The lack of LH leads to the degeneration of the corpus luteum with a subsequent drop in progesterone levels leading to menstruation
.Menstruation involves the loss of the inner layer of the endometrium accompanied by a small volume of blood for a few days

Question 26

What happens if fertilisation does occur?

Answer 26

.The corpus luteum does not degenerate and progesterone levels remain high preventing menstruation from taking place