Virtual period: sex hormones and puberty

Sex hormones are responsible of the most dramatic changes that occur in the body. They control puberty, egg and sperm production, pregnancy, birth and lactation.

  1. Read the information about Puberty HERE.
  2. State the female and male hormones which are responsible for the development of the secondary sexual characteristics
  3. Build a comparison table between the changes that occur in male and female after puberty.
  4. Search in the internet and summarize the site of production and effects of the following sex hormones:

– FSH, LH, oestrogen, progesterone, oxytocine, Hcg, prolactine and testosterone.

5. The chart shows the ages at which the changes associated with puberty take place in boys and girls. Answer questions a, b, c, d and e.

(a) What is the most common age at which boys undergo the changes of puberty?

(b) If a girl had not started menstruation by the age of 15, would this be cause for concern?

(c) Which two features of puberty show the greatest range in the times at which they  occur.


(d) Is it unusual for a girl of 9 years to start her menstrual periods?

(e) On average, is it boys or girls who first show the onset of puberty?


2. The female hormones responsible for the development of the secondary sexual characteristics are; oestrogen and progesterone. This hormones make women breast grow, public hair grow and develop wide hips. The male hormone responsible for the development of the secondary sexual characteristics is testosterone. These hormones are stimulated by Luteinising Hormone (LH) and Follicle Stimulating Hormone (FSH) . This hormone makes the men body hair grow, the voice break and the muscles growth increase.



  • FSH: It is produced by the pituitary gland and it:
    • Causes an egg to mature in an ovary.
    • Stimulates the ovaries to release the hormone oestrogen.
  • LH: It causes the mature egg to be released from the ovary.
  • Oestrogen: It is secreted by the ovaries and it:
    • Stops FSH being produced – so that only one egg matures in a cycle.
    • Stimulates the pituitary gland to release the hormone LH.
  • Progesterone: It is secreted by ovaries. It maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy.
  • Oxytocin: It is a hormone produced by the hypothalamus and secreted by the pituitary gland. This important hormone plays a crucial role in the childbirth process and also helps with male reproduction.
  • HCG: It is a hormone produced by the placenta after implantation. Human chorionic gonadotropin interacts with the LHCG receptor of the ovary and promotes the maintenance of the corpus luteum during the beginning of pregnancy.
  • Prolactin: It is a hormone produced in the pituitary gland, named because of its role in lactation. It also has other wide-ranging functions in the body, from acting on the reproductive system to influencing behaviour and regulating the immune system.
  • Testosterone: It is a hormone that is responsible for many of the physical characteristics specific to adult males. It plays a key role in reproduction and the maintenance of bone and muscle strength.


a. The most common age is when they are 12.

b. No, the avarage age is between 12 and 13 years old. But it is normal.

c. The first menstrual period and the growth on breast and hair.

d. No, it is normal, but not very common.

e. Girls are usually developed first.

Pupil reflex


In pairs, add a video which shows the pupil reflex in your eyes.

Using your reflex actions´knowledge , sketch the sequence of the pupil reflex. State the stimulus, receptors, coordinator, effector, effect, response and all the neurones involved.

Stimulus —> receptors —> coordinator —> effector —> effect

Bright light —> cones —> brain —> muscles of the iris —> effect (circular muscles contract, radial muscles relax) —> response pupil constricts

Dim light —> nods —> brain —> muscles of the iris —> effect (circular muscles contract, radial muscles relax) —> response —> pupil dilates

What is the importance of this reflex?

The importance of the pupil reflex is controling the amount of light to prevent the retina from gettting damaged.

Booklet act: COMPLETE questions 1 b and c on page 9.