Puberty

Question 1

Describe the order in which secondary sexual characteristics appear in males. At what age does it begin? (7)

Answer 1

Testicular Development
Pubic hair growth 
Spermatogeneis 
Growth spurt
Penile enlargement
Adult distribution of pubic hair. 
Begins at 10-14 years.

Question 2

Describe the order in which secondary sexual characteristics appear in females. At what age does it begin? What other characteristic can be used to estimate start time? (8)

Answer 2

Thelarche (breast bid development)
Pubic hair growth 
Growth spurt
Menarche (period begins)
Adult pattern pubic hair
Breasts finish development.
Begins at 9-13 years - apx 47kg.

Question 3

What scale is used to determine the progression of secondary sexual characteristics? (1)

Answer 3

Tanner scale.

Question 4

Describe the HPG axis. (6)

Answer 4

Hypothalamus > GnRH» Pituitary > LH+FSH» Gonad > Androgens and oestrogens.

Question 5

What is precocious puberty? (1)

Answer 5

When GnRH is raised too early and puberty begins inappropriately early.

Question 6

What defines the initiation of puberty? (2)

Answer 6

Nocturnal GnRH pulsility preceding physical change, but slowly increases LH and FSH which will prompt the changes.

Question 7

Describe GnRH in the body. (5)

Answer 7

Secreted in pulses.
Acts on membrane receptors and uses second messengers
Stimulates synthesis and release of pituitary hormones
Stimulates hyperplasia and hypertrophy of target tissue
Regulates its own receptor.

Question 8

Describe the effects of LH and FSH on men. (4)

Answer 8

LH stimulates Leydig cells to produce testosterone from cholesterol - LH is pulsatile so testosterone is highest in the morning.
Sertoli cells of the seminiferous tubules provide nutrition to the germ cells, are sensitive to FSH and secrete inhibin.

Question 9

Describe the effects of LH and FSH on women. (4)

Answer 9

FSH and LH work on gonads via Ga-s. They target granulosa and Theca interna cells to stimulate sex hormone and oocyte production.

Question 10

Describe the different levels of feedback on the HPG axis. (6)

Answer 10

Moderate oestrogen causes negative feedback - reduced GnRH.
Excessive oestrogen causes positive feedback - increased GnRH - LH only surge because inhibin still exists.
Progesterone - prevents positive feedback of high oestrogen - reduced GnRH - no LH surge.

Question 11

Describe inhibin. (3)

Answer 11

Produced by granulosa cells of the ovary or Sertoli cells of the testicle. Inhibits FSH secretion only.

Question 12

Describe leptin. (4)

Answer 12

Adipocyte-derived protein hormone
Signals about energy stores
Pulsitile release
Can regulate GnRH levels outside of LH control.