Hormonal Control of Reproduction Flashcards
Hormone
Chemical substance, produced by a gland and carried in blood, which alters activity of specific target organs (and is the destroyed by liver).
Pituitary gland
‘Master gland’ situated at base of brain
Examples of glands
Thyroid - thyroxine
Adrenal - adrenaline
Ovaries - Oestrogen
Testes - testosterone
Hormones are involved in control of…
Onset puberty, menstrual cycle and sperm production
Ages of puberty
10-16
Changes occur during puberty due to…
hormones
Onset of puberty
Hypothalamus gland in brain begins to secrete a releaser hormone which targets pituitary gland
Releaser hormone stimulates pituitary gland to release what 2 hormones?
- FSH follicle stimulating hormone
- Interstitial Cell stimulating hormone ICSH / Luteinising hormone (LH)
How do these hormones travel and where to?
Through blood to ovaries and testes
In Males
ICSH stimulates testes to produce testosterone - causes development of male sexual organs and male secondary sexual characteristics
In females
LH stimulates ovaries to produce oestrogen - causes development of female sexual organs and female secondary sexual characteristics
FSH promotes/where
Sperm production in seminiferous tubules
ICSH promotes what/where?
Interstitial cells to release testosterone
Testosterone stimulates what/where
Sperm production in seminiferous tubules and activates prostate gland and seminal vesicles to produce their secretion
Release of testosterone negative feedback system
- build up of testosterone concentration in blood inhibits secretion of FSH and ICSH in pituitary gland
- reduction of FHS and ICSH results in drop in production of testosterone
- reduction of testosterone concentration in blood stops inhibition of ICSH and ICSH production
- production and release of FSH and ICSH increases, stimulating increase production of testosterone.
How long does menstrual cycle last?
28 days
When is day one of menstrual cycle?
First day of period - blood - loss of lining of uterus with a limit
Day 5 of menstruation
Loss of blood stops
The lining of uterus begins to re-grow and an egg cell starts to mature in one of the ovaries
Around day 14 of menstruation
Mature egg is released form ovary - this is called ovulation. Egg travels through oviduct towards uterus
If egg doesn’t meet a sperm cell in oviduct
Lining of uterus begins to break down and cycle repeats
FSH
Causes the maturation of an egg in the ovary
pituitary gland
LH
Stimulates release of egg
pituitary gland
Oestrogen
Involved in repairing and thickening of uterus lining
ovaries
Progestrone
Maintains uterus lining
Ovaries
Oestrogen in cycle
Gradually increases and peaks approx on 12th day
Drops days 13 and 14
Progesterone in cycle
Stay approx at same level and begins to increase slightly from around day 12
Menstrual cycle is controlled by negative feedback loop
- The pituitary gland produces FSH which causes the development of a follicle in ovary
- As egg develops inside the follicle, the follicle produces hormone oestrogen
- Oestrogen causes growth and repair of lining of uterus wall. Oestrogen inhibits FSH
- When oestrogen rises to a high enough level it causes a surge in LH from pituitary gland which causes ovulation where an egg is released from follicle (day 14 of cycle).
- The follicle becomes the corpus luteum and this produces oestrogen and progesterone which inhibits FSH and LH production by pituitary. This is example of negative feedback.
- progesterone maintains uterus lining
- If egg fails to be fertilised, corpus luteum dies and progesterone levels drop. This causes menstruation, where the uterus lining breaks down - period
If women becomes pregnant
Placenta produces progesterone
This maintains lining of uterus during pregnancy and means menstruation does not happen
