U2 KA2 - Hormonal Control Of Reproduction

Question 1

What hormonal changes occur at puberty?

Answer 1

At puberty, the hypothalamus secretes a releaser hormone whose target is the pituitary gland (another hormone-releasing gland)

Once the pituitary gland is stimulated, two hormones are produced​

• FSH – follicle-stimulating hormone​
  *ICSH – Interstitial cell-stimulating hormone ​(In men)
  *LH – Luteinising hormone ​(In women)

The release of these hormones during puberty triggers the onset of sperm production in men and the menstrual cycle in women

Question 2

Explain the Production of Semen in Terms of Hormonal Control

Answer 2

1. The Hypothalamus causes the release of releaser hormon which stimulates the pituitary gland
2. The pituitary gland regulates secretion of ICSH and FSH
3. FSH arrives at the testes in the bloodstream and promotes the production of sperm in the seminiferous tubules
4. When ICSH arrives in the testes, interstitial cells are stimulated to produce testosterone.
5. Testosterone stimulates sperm production by activating the prostate gland and seminal vesicles
6. The Accessory glands then produce semen

Question 3

Describe negative feedback control in terms of sperm production

Answer 3

The production of testosterone is also self-regulated by a negative feedback system ​

The build up of testosterone inhibits the secretion FSH and ICSH from the pituitary gland -> decreasing testosterone production ​

If testosterone concentration in the blood decreases, inhibition of FSH and ICSH is reversed -> FSH and ICSH concentration increase -> testosterone production increases

Question 4

How long is the menstrual cycle and when does it start?

Answer 4

Around 28 days long and starts on the first day of menstruation

Question 5

Effect of FSH on Ovaries

Answer 5

FSH stimulates development and maturation of follicle.​

It also stimulates ovary tissue to secrete the sex hormone oestrogen.​

Question 6

Effect of LH on Ovaries

Answer 6

LH triggers ovulation ​

It also prompts the development of the corpus luteum from the follicle and stimulates the corpus luteum to secrete the sex hormone progesterone

Question 7

Effect of Oestrogen on Uterus and pituitary gland

Answer 7

Oestrogen stimulates the proliferation of the endometrium. ​

This repairs the uterus lining following menstruation and prepares for potential implantation. ​

Oestrogen also stimulates secretion of LH by the pituitary gland

Question 8

Effect of Progesterone on Uterus and pituitary gland

Answer 8

Progesterone promotes the further development and vascularisation of the endometrium.

Progesterone also inhibits the secretion of the pituitary hormones (FSH and LH)

Question 9

What are the 3 phases of ovulation

Answer 9

1. Follicular Phase
2. Ovulation
3. Luteal Phase

Question 10

Describe the Follicular Phase

Answer 10

The FSH released from the pituitary gland during the first half of the stimulates​
* Development and maturation of a follicle​
* The production of oestrogen by ovarian tissues ​

​In turn, the increase in oestrogen ​
*helps to repair the endometrium​
*triggers a surge in the production of LH around day 14

Question 11

Describe the Ovulation

Answer 11

The surge in LH around day 14 results in ovulation and an egg is released from the ovary. ​
The egg is moved slowly along the oviduct. ​

There is a window of 3-4 days when fertilisation may occur if the egg cell meets a sperm.

Question 12

Describe the Luteal Phase

Answer 12

After ovulation, the peak LH levels stimulates the follicle in the ovary to become a corpus luteum​

The corpus luteum secretes oestrogen and progesterone​

an increased progesterone concentration further stimulates the development of the endometrium to prepare for implantation

The combined high levels of oestrogen and progesterone during the luteal phase results in a inhibition of the release of the pituitary gland hormones; FSH and LH​

This is another example of negative feedback as the drop in FSH and LH concentrations leads to no new follicles developing in the ovary.