1. Hormonal control of Reproduction

2. Learning Outcomes
Pituitary gland is stimulated to release FSH, LH, and ICSH by a releaser hormone produced in the hypothalamus
Hormonal control of sperm production
FSH promotes sperm production
ICSH stimulates the production of testosterone
Testosterone stimulates sperm production
Testosterone activates the Seminal vesicles and Prostate Gland
As testosterone concentration increases to a certain level this inhibits FSH and ICSH secretion
Testosterone level decreases
Pituitary releases FSH and ICSH again –
This self-regulating mechanism is ‘negative feedback control’

3. Hormones
Hormones are ‘chemical messengers’ produced by Endocrine Glands Hormones are secreted into the bloodstream When they reach a ‘target organ’ they bring about a specific effect In reproduction, hormones control – the onset of puberty sperm production the menstrual cycle

4. Hypothalamus
Brain
Pituitary

6. Onset of Puberty
At puberty the Hypothalamus secretes a releaser hormone whose target is the Pituitary Gland The pituitary responds by producing two hormones The first is FSH, follicle stimulating hormone In males, the second is ICSH (interstitial cell-stimulating hormone) In females, the second is LH (luteinising hormone)

7. Hormonal control of sperm production
FSH promotes sperm production in the seminiferous tubules ICSH stimulates the interstitial cells to produce the hormone Testosterone Testosterone – stimulates sperm production activates the Seminal Vesicles and Prostate Gland to produce secretions

8. Seminiferous tubules – sperm production here
Coiled Tubes
Leading to sperm duct
Seminiferous tubules – sperm production here

9. Negative Feedback Control
As testosterone concentration builds up in the bloodstream it reaches a level that inhibits FSH and ICSH secretion This leads to a decrease in testosterone concentration As a result, the pituitary gland releases FSH and ICSH again This type of self regulating mechanism is called negative feedback

10. Pituitary hormones and Ovaries
FSH stimulates the development and maturation of each follicle It also stimulates the ovary to secrete the female sex hormone Oestrogen LH triggers ovulation It also brings about the development of the corpus luteum from the follicle The corpus luteum then secretes the sex hormone Progesterone

11. Ovary- secretes Oestrogen
Mature Follicle
Corpus luteum -progesterone
Ovulation

12. Oestrogen
Oestrogen stimulates the proliferation of the Endometrium, the inner layer of the uterus This prepares the uterus for implantation of an embryo High levels of oestrogen stimulates the cells lining the cervix to secrete a watery mucus easily penetrated by sperm The highest concentration of oestrogen is just before ovulation (increases chance of fertilisation)

13. Progesterone
Oestrogen also stimulates the production of LH by the pituitary Progesterone – promotes the further development and vascularisation of the endometrium, in preparation to receive a blastocyst progesterone inhibits the secretion of FSH and LH by the pituitary

14. Try these questions
Name three reproductive processes that hormones control
Name two female hormones produced by the pituitary
What does testosterone do?
What does high levels of oestrogen do to the cells lining the cervix?
Name the two hormones that progesterone inhibits

15. Answers
the onset of puberty, sperm production, the menstrual cycle
FSH and LH
Stimulates sperm production and activates the Seminal Vesicles and Prostate Gland to produce secretions
High levels of oestrogen stimulates the cells lining the cervix to secrete a watery mucus easily penetrated by sperm
FSH and LH by the pituitary gland

16. Glossary
CORPUS LUTEUM – the ‘yellow body’ which forms from the follicle after ovulation
ENDOMETRIUM – the lining of the uterus
FOLLICULAR PHASE – phase of the menstrual cycle during which follicles in the ovary mature. This phase ends at ovulation
FOLLICLE STIMULATING HORMONE (FSH) – a pituitary hormone which stimulates the development of a ball of cells round the ovum
INTERSTITIAL CELLS – cells found between the seminiferous tubules of the testes, which produce testosterone
INTERSTITIAL CELL STIMULATING HORMONE (ICSH) - hormone produced by the anterior lobe of the pituitary gland that, in the male, stimulates the interstitial cells of the testes to produce testosterone
LUTEAL PHASE – stage of the menstrual cycle which occurs after ovulation and before a period starts. During this phase, the lining of the womb thickens.

17. LUTENISING HORMONE (LH) – a pituatry hormone which stimulates ovulation
OESTROGEN – a hormone involved in the menstrual cycle with a variety of functions
PROGESTERONE – a hormone produced by the corpus luteum, involved in the menstrual cycle
PROSTATE – gland of the male reproductive system which contributes fluid to the semen
SEMINAL VESICLE – a gland of the male reproductive system which contributes fluid to the semen
SEMINAL FLUID (SEMEN) – fluid which carries the sperm from the testes out of the penis during ejaculation
SEMINIFEROUS TUBULES – tubules of the testes in which sperm are made
TESTOSTERONE – a sex hormone which promotes male characteristics and sperm production