1. Higher Human Biology Unit 2 – Physiology and Health
Section 10 – Hormonal Control of Reproduction

2. What Can You Remember? What are hormones?
How are hormones transported?
What type of molecules are proteins?
What do hormones bind onto?
Where are sperm produced?
What gamete is produced in the ovary?
What cells produce testosterone?
What does the Graafian follicle mature into?
What hormone does the Graafian follicle produces after ovulation?
chemical messengers
In the blood
Polypeptides
Specific receptor
Testes
Ovum
Interstitial cells
Corpus Luteum
Progesterone

3. a – Hormonal Influence on Puberty
We will be learning…
To state that the pituitary gland becomes stimulated by a gonadotrophic releaser hormone.
State that the pituitary gland then goes on to release hormones that trigger the onset of puberty
To be able to describe the role of the pituitary gland in releasing Follicle Stimulating Hormone (FSH)
To be able to describe the role of the pituitary gland in releasing Luteinising Hormone (LH)
To be able to describe the role of the pituitary gland in releasing Interstitial Cell Stimulating Hormone (ICSH)

4. Puberty
Puberty is the sequence of physical changes by which the human body develops from that of a child into that of an adult capable of reproduction. The process is initiated by a releaser hormone that is secreted by the hypothalamus. The target is the pituitary gland.

5. Where is your Hypothalamus & Pituitary Gland?
The Pituitary gland is located in the centre of the brain and produces many hormones. The hypothalamus is located centrally next to the pituitary gland.
Hormones are chemical messengers produced by an animal’s endocrine glands and secreted directly into the bloodstream. When a hormone reaches a certain target tissue, it brings about a specific effect.

6. What is the Role of Pituitary Gland?
Pituitary gland is a gland that produces many hormones in response to the releaser hormone.
Two of these are called gonadotrophic hormones because their target are the gonads (reproductive organs).
FSH –Follicle stimulating hormone – stimulates gamete production in both males and females
In men - ICSH – Interstitial Cell Stimulating hormone.
In women – LH – Luteinising hormone
These hormones are released at puberty which triggers sperm production in men and the menstrual cycle in women.

7. FSH – Follicle Stimulating Hormone
FSH initiates gamete production by means of the development of follicles in the ovaries, and sperm production in the seminiferous tubules.

8. Role of LH – Luteinising Hormone
FSH and LH act together to stimulate the production of oestrogen from the ovarian follicles, although LH prompts the corpus luteum to release progesterone after ovulation.

9. Role of ICSH – Interstitial Cell Stimulating hormone
ICSH in the male stimulates the release of testosterone from the interstitial cells of the testis.

10. b – Hormonal Control of Sperm Production
We will be learning…
To describe the role that FSH plays in promoting sperm production
To describe the role that ICSH plays in stimulating the production of testosterone
State that testosterone also stimulates sperm production and activates the prostate gland and seminal vesicles.
To be able to describe negative feedback control of testosterone by FSH and ICSH

11. Role of FSH in Sperm Production
Sperm production is directly controlled by the pituitary gland through the secretion of FSH and indirectly through the secretion of ICSH.
FSH stimulates the cells lining the seminiferous tubules to divide to produce sperm
ICSH causes the interstitial cells between the tubules to release testosterone which helps the spermatozoa to mature into motile sperm cells.

12. Role of ICSH in Stimulating Testosterone Production
ICSH causes the interstitial cells, in the testes, between the tubules to release testosterone, which then plays a major role in promoting sperm production. As well as promoting the production of sperm, testosterone also activates the prostate gland and the seminal vesicles which produce their secretions that contribute to seminal fluid.

13. Role of Testosterone
Testosterone is involved in the development of the male secondary sex characteristics e.g. stimulates hair growth, enlargement of the penis, larynx and promotes muscle development over fat.

14. Negative Feedback Control of Testosterone by FSH and ICSH
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. Since this leads in turn to a decrease in testosterone concentration, it then stimulates the pituitary gland to make more FSH and ICSH again.

15. Negative Feedback Control of Testosterone by FSH and ICSH

16. c – Hormonal Control of the Menstrual Cycle
We will be learning…
To be able to describe the 28 days of the menstrual cycle
To state that the menstrual cycle can be described as the follicular phase and the luteal phase
To state that FSH stimulates the development of a follicle and the production of oestrogen in the follicular phase
To describe how oestrogen goes on to stimulate proliferation of the endometrium in preparation for implantation.
To explain how the consistency of the cervical mucus changes in response to oestrogen
To state that when oestrogen levels peak this stimulates secretion of LH which triggers ovulation.
To describe the luteal phase as the follicle develops into the corpus luteum which secretes progesterone
To explain the role that progesterone plays in preparing for implantation if fertilisation occurs
To describe the role that negative feedback has on the pituitary gland
To be able to interpret graphs showing changes in FSH, LH oestrogen and progesterone concentrations

17. The Menstrual Cycle
The ovarian hormones oestrogen and progesterone, and the pituitary hormones FSH and LH interact with each other to coordinate the menstrual cycle.
The menstrual cycle is a repeating series of changes in the levels of the above hormones which is accompanied by changes in the development of the Graafian follicle and the lining of the uterus (the endometrium).
The average length of a cycle is 28 days, although it can vary greatly from one individual to another.
The first day of menstruation, that is the start of the monthly 'period', is usually regarded as day 1 of the cycle.

18. The Menstrual Cycle
The menstrual cycle in humans lasts approximately 28 days with the first day of menstruation being counted as day 1. Menstruation usually lasts about four days (but anything from 2-7 days is considered normal) and ovulation typically occurs at day 14. The first part of the cycle, from menstruation to ovulation, is known as the follicular phase; the second part, from ovulation to the start of menstruation, is the luteal phase.

19. The menstrual cycle can be divided into two parts:
Follicular Phase
First half - from day 1 (the start of menstruation) to about day 14 (when ovulation occurs)
Luteal Phase
Second Half - from day 14 to day 28, when menstruation begins again.
FOLP

21. Follicular Phase
Initially, Oestrogen and progesterone levels are low and, as a result of negative feedback control, the pituitary is releasing a high level of FSH. This prompts the development of a follicle in the ovary; as it grows, it releases increasing quantities of oestrogen, which inhibits the release of FSH by the pituitary.

22. Role of FSH in stimulating the development of a follicle and the production of oestrogen
FSH from the pituitary gland
stimulates the development and maturation of the Graafian follicle
produces oestrogen by the ovary

23. Role of Oestrogen
Oestrogen also promotes the proliferation of the endometrium of the uterus. This mean that it becomes thicker and vascularised with a dense system of blood vessels. This is in preparation to support the blastocyst if the ovum is fertilised.

24. Role of Oestrogen
Oestrogen also alters the viscosity of the mucus lining of the cervix, making it more watery and ultimately easier for the sperm to swim through.
As the concentration of oestrogen in the blood rises, it eventually reaches a critical level at which the pituitary responds by releasing a surge of LH. This sudden increase in LH concentration causes the follicle, which has moved to the surface of the ovary, to rupture and release the ovum into the oviduct. This marks the end of the follicular phase of the menstrual cycle.

25. Luteal Phase
Around day 14, after ovulation, the follicle develops into the corpus luteum under the influence of high levels of LH. The corpus luteum then begins to increase the production of progesterone, reaching a peak in production about halfway through the luteal phase.

26. Luteal Phase Increasing progesterone levels promote…..
the thickening and vascularisation (build up of blood vessels) of the endometrium, in preparation for the implantation of the blastocyst;
high levels of progesterone inhibit the secretion of FSH and LH by the pituitary gland;
As the levels of LH decrease the corpus luteum begins to degenerate (around day 22).
This causes the levels of progesterone to decrease until by around day 28 of the cycle the endometrium can no longer be maintained.
endometrium breaks down and is passed out of the body (menstruation).
The decrease in progesterone levels removes its inhibitory effect on the pituitary gland, which begins to secrete more FSH again.
As the levels of FSH rise the cycle begins again.

28. If Fertilisation Occurs….
If the ovum is fertilised, it develops into the blastocyst as it is carried down the oviduct. About nine days after fertilisation, the blastocyst implants in the endometrium and begins to secrete a hormone which causes the corpus luteum to continue to release progesterone until this function is assumed by the placenta some two months later.

29. Menstrual cycle- Hormonal Control
(a) changes in levels of the pituitary hormones FSH and LH;
(b) development of the Graafian follicle;
(c) changes in the levels
of the ovarian hormones oestrogen and progesterone
(d) changes in the thickness of the endometrium.

31. Menstrual cycle – Changes
Two other changes which take place during the menstrual cycle are changes to the
Cervix
Body Temperature.

32. Cervical Mucus Changes
The changes which occur to the cervix play a role in fertility.
The cells of the cervix secrete mucus.
High levels of oestrogen stimulate these cells to produce a thin and watery mucus and cervix becomes slippery and stretchy which is easily penetrated by sperm.
Since the highest levels of oestrogen occur just before ovulation, the production of thin mucus at this time increases the chances of fertilisation.
High levels of progesterone, on the other hand, cause the mucus secreted by the cervical cells to become thicker and, if pregnancy occurs, change into a semi-solid 'plug', which helps to protect the developing embryo against infection.

33. Diagram of changes to the cervix during menstrual cycle.

34. Changes to Body Temperature
A woman's body temperature rises by as much as 0.5°C at ovulation.
These changes in body temperature and the viscosity of cervical mucus can be used as indicators of ovulation and forms the basis of the rhythm method of birth control (see later).

36. Now I can….. a – Hormonal Influence on Puberty
State that the pituitary gland becomes stimulated by a gonadotrophic releaser hormone.
State that the pituitary gland then goes on to release hormones that trigger the onset of puberty
Describe the role of the pituitary gland in releasing Follicle Stimulating Hormone (FSH)
Describe the role of the pituitary gland in releasing Luteinising Hormone (LH)
Describe the role of the pituitary gland in releasing Interstitial Cell Stimulating Hormone (ICSH)

37. b – Hormonal Control of Sperm Production
Now I can…..
Describe the role that FSH plays in promoting sperm production
Describe the role that ICSH plays in stimulating the production of testosterone
State that testosterone also stimulates sperm production and activates the prostate gland and seminal vesicles.
Describe negative feedback control of testosterone by FSH and ICSH

38. Now I can….. c – Hormonal Control of the Menstrual Cycle
Describe the 28 days of the menstrual cycle
State that the menstrual cycle can be described as the follicular phase and the luteal phase
State that FSH stimulates the development of a follicle and the production of oestrogen in the follicular phase
Describe how oestrogen goes on to stimulate proliferation of the endometrium in preparation for implantation.
Explain how the consistency of the cervical mucus changes in response to oestrogen
State that when oestrogen levels peak this stimulates secretion of LH which triggers ovulation.
Describe the luteal phase as the follicle develops into the corpus luteum which secretes progesterone
Explain the role that progesterone plays in preparing for implantation if fertilisation occurs
Describe the role that negative feedback has on the pituitary gland
Interpret graphs showing changes in FSH, LH oestrogen and progesterone concentrations

39. Word
Meaning
Blastocyst
cellular structure that implants and becomes the embryo and the placenta
Corpus Luteum
formed from a follicle after ovulation;produces progesterone
Endometrium
inner lining of the uterus
Follicle
cluster of cells in the ovary that matures to release an ovum
Gamete
sex cell containing the haploid chromosome number
Interstitial Cells
cells in testes found between the seminiferous tubules; stimulated by ISCH to produce testosterone
Oestrogen
hormone produced by the ovary that helps in the repair and thickening of the endometrium after menstruation
Ovaries
female sex organsin which ova are produced
Oviduct
fine tube connecting an ovary to the uterus;location of fertilisation
Progesterone
hormone produced by the ovary that thickens and vascularises the endometrium
Prostate Gland
produces fluid that makes up part of the semen
Seminal Vesicles
glands producing fluid that forms part of the semen

40. very narrow tubes in the testes in which sperm cells are produced
Word
Meaning
Seminiferous Tubules
very narrow tubes in the testes in which sperm cells are produced
Testes
male sex organs responsible for the production of sperm
Testosterone
steroid hormone produced by interstitial cells
Zygote
fertilised egg cell
Endocrine Gland
gland that produces and releases hormones
Follicle Stimulating Hormone (FSH)
pituitary hormone that controls development of follicles in ovaries and sperm production in males
Follicular Phase
first stage in the menstrual cycle during which a follicle develops
Hormone
protein released by an endocrine gland into the blood that acts as a chemical messenger
Hypothalamus
region of the mammalian brain that secretes releaser hormone at puberty
Interstitial cell stimulating hormone (ICSH)
hormone from pituitary gland that stimulates testosterone production in seminiferous tubules

41. Luteinising Hormone (LH)
Word
Meaning
Luteal Phase
second stage of the menstrual cycle in which a corpus luteum is present
Luteinising Hormone (LH)
pituitary hormone that triggers ovulation and corpus luteum development
Menstrual Cycle
approximately 28-day cycle in the middle of which ovulation occurs
Menstruation
removal of the endometrium and an unfertilised egg cell at the end of a menstrual cycle
Negative Feedback
system of maintaining a steady state in various body systems
Pituitary Gland
gland in the brain that releases many hormones

42. Give an account of negative feedback control under the headings:
testosterone production; (3 marks)
the luteal phase of the menstrual cycle. (7 marks)

43. Testosterone production (maximum of 3 marks):
The pituitary gland releases ICSH.
ICSH stimulates the interstitial cells of the testes to release testosterone.
Increasing level of testosterone inhibits/reduces the production/release of ICSH.
Pituitary gland releases less ICSH…
…so testes/interstitial cells release less testosterone.
The luteal phase of the menstrual cycle (maximum of 7 marks):
After ovulation, the high level of LH causes the follicle to develop into the corpus luteum.
The corpus luteum secretes progesterone and oestrogen.
During this phase the secretion of oestrogen and progesterone rise to a maximum and then decline.
The high levels of oestrogen inhibit the pituitary from secreting FSH.
The high levels of progesterone inhibit the pituitary from secreting LH.
The resulting low level of FSH suppresses the development of further follicles.
The low level of LH causes the corpus luteum to degenerate…
…and progesterone secretion to fall to a minimum.
The falling level of progesterone at the end of the cycle triggers the start of menstruation.
The low level of oestrogen at the end of the cycle causes the pituitary to increase secretion of FSH.

44. HHB 201 ? Question ? C