AQA GCSE Hormones and human reproduction (Biology)

AQA GCSE Hormones and human reproduction(Biology)

Hormones and human reproduction

As a result of puberty hormones trigger secondary sexual characteristics.

Secondary sexual characteristic	Male, female or both
Breast development	Female
Facial hair growth	Male
Body hair growth	Both
Voice breaking	Male
Menstruation starts	Female
Sperm production starts	Male

Main reproductive hormones

The two main reproductive hormones are:

1.Oestrogen in females.

2.Testosterone in males.


	Oestrogen	Testosterone
Site of production	Ovaries	Testes
Effects	Inhibits the release of FSH, stimulates the release of LH Rebuilds and thickens the uterus lining Causes secondary sexual characteristics	Stimulates sperm production Causes secondary sexual characteristics

Menstrual cycle

The menstrual cycle begins at puberty in females. Each cycle lasts about 28 days, and during each cycle one egg is released. The menstrual cycle stops when menopause begins.

Day 1–5 of the menstrual cycle is menstruation. During this time the uterus lining is broken down and discharged from the body. This is known as a period.

Day 5–14 the uterus lining is rebuilt and thickens. Around day 14 ovulation occurs.

Day 14–28 the uterus lining is maintained. If the egg is not fertilised by day 28, hormone levels fall, the uterus lining breaks down and the cycle restarts.

If the egg is fertilised, the uterus lining is maintained throughout pregnancy.

Role of the hormones in the menstrual cycle.

Below is a summary table for the four main hormones involved in the menstrual cycle.

Hormone	Where it is produced	Role in menstrual cycle
FSH (Follicle stimulating hormone)	Pituitary gland	Causes an egg to mature in the ovary and stimulates oestrogen production
Oestrogen	Ovary	Rebuilds and thickens the uterus lining, inhibits release of FSH, stimulates LH release
LH (Luteinising Hormone)	Pituitary gland	Triggers ovulation (release of egg from ovary)
Progesterone	Ovary(after ovulation)	Maintains uterus lining, inhibits FSH and LH, drop in levels of progesterone causes menstruation

Day 1–5:
FSH is released and causes an egg to mature in the ovary.

Day 6–13:
The ovary secretes oestrogen, which rebuilds the uterus lining.
As oestrogen levels rise, FSH release is inhibited and LH release is stimulated.

Day 14:
LH levels peak, causing ovulation. The egg is released from the ovary.

Day 15–28:
The ovary secretes progesterone, which maintains the uterus lining and inhibits FSH and LH release.
If the egg is not fertilised, progesterone levels fall and the cycle restarts.

See the graph below