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Think about…
4.1 Hormonal control of the
menstrual cycle
4.2 Use of hormones
Recall ‘Think about…’
Summary concept map
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The performance of
female athletes may
be affected by their
physiological
conditions before or
during menstruation.
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Some athletes may take
drugs to prevent menstruation
from occurring during sports
games.
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The drugs contain hormones
which are similar to those
naturally produced in the
female body.
What are the hormones involved?
How do the drugs prevent menstruation?
Can menstruation be resumed later?
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4.1 Hormonal control of the
menstrual cycle
Let’s revise the
menstrual cycle first.
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The menstrual cycle
Cycle repeats
until meno…
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The maturation and release of egg cells from the ovary
are synchronized with changes in the uterus
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The Ovarian Cycle
• In the ovarian cycle
– Hormones stimulate follicle growth, which results in
ovulation
• Following ovulation
– The follicular tissue left behind transforms into the
corpus luteum
 Three phases: follicular --- ovulation --- luteal
(1-14)
(14)
(14-28)
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The Uterine Cycle
Three phases : Menstrual -- proliferative ------- secretory
(1-6)
(6-14)
(14-28)
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4.1 Hormonal control of the menstrual cycle
Day 1 to 5 of the menstrual cycle
• uterine lining breaks
down
• follicle begins to
develop
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4.1 Hormonal control of the menstrual cycle
Day 5 to 14 of the menstrual cycle
• uterine lining begins
to thicken
• follicle becomes
mature
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4.1 Hormonal control of the menstrual cycle
Day 14 of the menstrual cycle
• uterine lining
becomes very thick
• ovulation occurs
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4.1 Hormonal control of the menstrual cycle
Day 14 to 28 of the menstrual cycle
• uterine lining
remains thick
• ovum is moved
along the oviduct
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4.1 Hormonal control of the menstrual cycle
What are the
hormones involved?
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4.1 Hormonal control of the menstrual cycle
• events synchronized by the
interaction of four hormones:
pituitary
gland
follicle stimulating
hormone (FSH)
luteinising hormone
(LH)
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4.1 Hormonal control of the menstrual cycle
• events synchronized by the
interaction of four hormones:
yellow
body
follicle
oestrogen
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4.1 Hormonal control of the menstrual cycle
• events synchronized by the
interaction of four hormones:
yellow
body
progesterone
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4.1 Hormonal control of the menstrual cycle
How do the
hormones interact?
• the hormones interact by feedback
mechanisms
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4.1 Hormonal control of the menstrual cycle
ovary
pituitary
gland
stimulation
 FSH
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4.1 Hormonal control of the menstrual cycle
pituitary
gland
ovary
 follicle develops
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4.1 Hormonal control of the menstrual cycle
pituitary
gland
ovary
 Above a certain level, oestrogen
stimulates FSH and LH secretion
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4.1 Hormonal control of the menstrual cycle
pituitary
gland
ovary
 LH
LH stimulates oestrogen secretion and oestrogen
stimulates FSH and LH secretion ….
A positive feedback effect at around day 14 that raise
LH to a peak level
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4.1 Hormonal control of the menstrual cycle
pituitary
gland
ovary
 ovulation
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4.1 Hormonal control of the menstrual cycle
pituitary
gland
ovary
yellow
body
 LH stimulates development of
yellow body and hence
progesterone secretion
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4.1 Hormonal control of the menstrual cycle
pituitary
gland
inhibition
ovary
 oestrogen and progesterone together
inhibit LH and FSH
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4.1 Hormonal control of the menstrual cycle
Let’s look at the menstrual
cycle from day 5.
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4.1 Hormonal control of the menstrual cycle
Before ovulation
1 The pituitary gland secretes FSH.
2 FSH stimulates the development
of follicles. As the follicle matures,
it secretes more oestrogen.
3 Under the action of oestrogen, the
uterine lining begins to thicken.
to chart
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4.1 Hormonal control of the menstrual cycle
Before ovulation
4 Oestrogen level continues to rise
and reaches a peak just before
ovulation. A high level of oestrogen
stimulates FSH and LH secretion.
The peaks of FSH and LH occur
just after the oestrogen peak.
5 A high level of LH causes
ovulation to occur on day 14.
to chart
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4.1 Hormonal control of the menstrual cycle
After ovulation
6 The remaining follicle cells form the
yellow body. A high level of LH
stimulates the yellow body to
secrete oestrogen and progesterone.
Oestrogen level rises again and
progesterone level reaches a peak.
7 Under the action of oestrogen and
progesterone, the uterine lining
to chart
remains thick.
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4.1 Hormonal control of the menstrual cycle
After ovulation
8 High levels of oestrogen and
progesterone together inhibit
FSH and LH secretion. A low level
of LH causes the yellow body to
degenerate around day 24.
to chart
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4.1 Hormonal control of the menstrual cycle
After ovulation
9 The yellow body gradually stops
secreting oestrogen and progesterone
and the thickened uterine lining soon
breaks down. Also, the inhibition of
oestrogen and progesterone on FSH
secretion is removed. The pituitary
gland secretes more FSH again and
the cycle repeats.
to chart
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4.1 Hormonal control of the menstrual cycle
levels of pituitary
hormones in
blood
events in ovary
levels of ovarian
hormones in
blood
thickness of
uterine lining
to text
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• Cyclic secretion of GnRH* from the hypothalamus
– And of FSH and LH from the anterior pituitary
orchestrates the female reproductive cycle
Five hormones
involved in an
elaborate scheme
involving both
positive and
negative feedback
*Gonadotropin-releasing hormone
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Hormone
Site of
Secretion
Follicle
Pituitary
Stimulating
gland
Hormone (FSH)
Oestrogen
Ovary
Lutenising
Pituitary
Hormone (LH)
Progestrone
Corpus
luteum
Target
Organ
Function
•stimulates the growth & development of the
follicle
Ovary
•stimulates secretion of oestrogen
•effect of LH in stimulating ovulation
•stimulates repair of uterine lining
Endometrium •at high conc. inhibits FSH, however during
(lining of the 'pituitary hormone surge' it stimulates further
uterus)
FSH production
•as conc. peaks stimulates release of LH
Ovary
•stimulates the final development of the follicle
•stimulates ovulation
•stimulates the development of the corpus
luteum
•stimulates production of progesterone
Uterus
•maintains uterine lining endometrium)
•inhibits release of FSH
•inhibits release of LH
•fall in conc. results in menstruation
•fall in conc. removes inhibition of FSH and a
new cycle begins.
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Feedback control of human menstrual cycle
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Atresia of corpus luteum -- degeneration and resorption of corpus luteum in ovary
Estradiol -- Oestrogen
Hormonal feedback control of menstrual cycle
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• The reproductive
cycle of the
human female
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• The reproductive
cycle of the
human female
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4.1 Hormonal control of the menstrual cycle
If fertilization occurs …
placenta
secretes
human chorionic gonadotrophin (HCG)
• acts like LH
• prevents degeneration of yellow body
 secretes oestrogen and progesterone
 uterine lining remains thick for embryo
development
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4.1 Hormonal control of the menstrual cycle
What is the significance of
hormonal control of the
menstrual cycle?
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4.1 Hormonal control of the menstrual cycle
i) Ensure one ovum is released at a
time
• after ovulation, high levels of oestrogen
and progesterone together inhibit FSH
and LH secretion
 prevents maturation of another follicle
Higher survival
chance!
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4.1 Hormonal control of the menstrual cycle
i) Ensure one ovum is released at a
time
• after ovulation, high levels of oestrogen
and progesterone together inhibit FSH
and LH secretion
 prevents maturation of another follicle
Avoid wasting of
energy!
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4.1 Hormonal control of the menstrual cycle
ii) Prepare for implantation
• oestrogen and progesterone stimulate
the thickening of the uterine lining
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4.1 Hormonal control of the menstrual cycle
iii) Prepare for the next possible
pregnancy
• if no fertilization occurs, levels of
oestrogen and progesterone fall which
causes menstruation to occur and the
pituitary gland secretes more FSH again
• the menstrual cycle repeats
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4.1 Hormonal control of the menstrual cycle
1 Hormonal
control of
menstrual
cycle:
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4.1 Hormonal control of the menstrual cycle
2 Significance of hormonal control
of the menstrual cycle:
a After ovulation,
high levels of
oestrogen and progesterone
together inhibit FSH and LH
secretion.
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4.1 Hormonal control of the menstrual cycle
2 Significance of hormonal control
of the menstrual cycle:
a This prevents the maturation of
another follicle and ensures only
one ovum is released in each
cycle. This would result in higher
survival chance of the foetus.
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4.1 Hormonal control of the menstrual cycle
2 Significance of hormonal control
of the menstrual cycle:
b Oestrogen and progesterone
stimulate the thickening of the
uterine lining to prepare for the
implantation of the embryo.
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4.1 Hormonal control of the menstrual cycle
2 Significance of hormonal control
of the menstrual cycle:
c If no fertilization occurs, levels of
oestrogen and progesterone fall
which causes menstruation to
occur. The pituitary gland begins
to secrete more FSH again.
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4.1 Hormonal control of the menstrual cycle
2 Significance of hormonal control
of the menstrual cycle:
c The menstrual cycle repeats to
prepare for the next possible
pregnancy.
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4.2 Use of hormones
• used as contraceptives or in the
treatments of infertility
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4.2 Use of hormones
How are hormones used to
prevent pregnancy?
• contraceptive pills contain synthetic
progesterone or a combination of
synthetic oestrogen and progesterone
 high levels inhibit FSH and LH
secretion
 follicle development and
ovulation do not occur
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4.2 Use of hormones
contraceptive pills
for 21 days
for 28 days
hormone-free
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4.2 Use of hormones
contraceptive patches and injections
to be replaced
weekly
to be taken every 3
months
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How the injection works (ref)
•
•
•
•
•
The contraceptive injection works in the same way as the implant. It steadily releases
the synthetic hormone progestogen into your bloodstream.
The continuous release of progestogen:
stops a woman releasing an egg every month (ovulation)
thickens the mucus from the cervix (neck of the womb), making it difficult for sperm to
pass through to the womb and reach an unfertilised egg
makes the lining of the womb thinner so that it is unable to support a fertilised egg
Disrupted periods
• Periods irregular and may be very heavy, or shorter and lighter, or stop altogether.
This may settle down after the first year, but may continue as long as the injected
progestogen remains in your body.
• It can take a while for your periods and natural fertility to return after you stop using
the injection. It takes around eight to 12 weeks for injected progestogen to leave the
body, but you may have to wait longer for your periods to return to normal if you are
trying to get pregnant.
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4.2 Use of hormones
• morning-after pills contain a high
dose of synthetic progesterone or a
combination of synthetic oestrogen
and progesterone
 prevent ovulation and
implantation
 prevent pregnancy after
sexual intercourse
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4.2 Use of hormones
They are not for regular
use and must be
prescribed by doctors.
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4.2 Use of hormones
How are hormones used to
treat infertility?
• causes of infertility:
- does not produce enough
sperm
- sperm have low motility
- sperm have structural
defects
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4.2 Use of hormones
How are hormones used to
treat infertility?
• causes of infertility:
- fails to release ova from the
ovaries
- oviducts are blocked
- uterine environment does
not allow implantation
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4.2 Use of hormones
• fertility drugs contain:
- FSH
 stimulates follicle development
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4.2 Use of hormones
• fertility drugs contain:
- LH
 stimulates ovulation
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4.2 Use of hormones
• fertility drugs contain:
- synthetic oestrogen and progesterone
 stimulates the thickening of the
uterine lining to prepare for
implantation of the embryo
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4.2 Use of hormones
1 Synthetic
oestrogen and
progesterone are present in
contraceptives. They inhibit FSH
and LH secretion by the pituitary
gland. This prevents follicle
development and ovulation, so
that no ova are released into the
oviducts for fertilization.
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4.2 Use of hormones
2a FSH, LH,
HCG , synthetic
oestrogen and progesterone are
present in fertility drugs.
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4.2 Use of hormones
2b FSH promotes
follicle
development. LH and HCG
stimulate ovulation . Synthetic
oestrogen and progesterone
stimulate the thickening of the
uterine lining to prepare for
implantation .
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1
What are the hormones present in
the drugs?
The drugs contain synthetic oestrogen
and progesterone.
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2
How do the drugs prevent
menstruation?
High levels of oestrogen and
progesterone in blood maintain the
thickness of the uterine lining to
prevent menstruation.
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3
How can menstruation be resumed?
Menstruation will resume after the
female has stopped taking the drugs.
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Menstrual cycle
is controlled by interaction of
pituitary
hormones
ovarian
hormones
can be used as
contraceptives
treatment
of fertility
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pituitary hormones
include
follicle stimulating
hormone (FSH)
stimulates
follicle
development
luteinising
hormone (LH)
ovulation
stimulates
yellow body
formation
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ovarian hormones
include
oestrogen
progesterone
stimulate
thickening of
uterine lining
low levels
cause
menstruation
to prepare for
implantation
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