Topic 7- Hormones, the Menstrual cycle and Fertility Flashcards
What are hormones?
Chemicals released directly into the blood that target specific organs, controlling things in organs or cells that need constant adjustment.
Where are hormones produced?
In endocrine glands
Describe the function of the pituitary gland
It produces many hormones that regulate body temperature and also act on other glands to release hormones.
Describe the function of the Thyroid gland
This produces thyroxide which regulates things like metabolism, heart rate and temperature.
Describe the function of the adrenal glands
These produce adrenaline which is used to prepare the body for ‘fight or flight’
Describe the function of the pancreas
This produces insulin which is used to regulate the blood glucose level.
What hormones do testes produce?
Testosterone which controls puberty and sperm production
What are the differences between neurones and hormones?
Neurones: very fast action, act for a short time and in a very precise area
Hormones: slower action, act for a long time and in a more general way
How does the hormone adrenaline prepare the body for ‘fight or flight’?
Adrenaline binds to specific receptors in the heart. This causes the heart muscle to contract more frequently and with more force so heart rate and blood pressure increase.
This increases blood flow to the muscles so the cells receive more oxygen and glucose for increased respiration.
Adrenaline also binds to the receptors in the liver which causes to breakdown it glucose stores so it releases glucose.
This increases blood glucose levels so they can be transported to cells.
How does the negative feedback system keep the right amount of thyroxine in the blood at the right level?
When the blood-thyroxine level is lower than normal, the hypothalamus is stimulated to release TRH.
TRH stimulates the pituitary gland to release TSH.
TSH stimulates the thyroid gland to release thyroxine, so the blood thyroxine level goes back to normal.
When the blood thyroxine level becomes higher than normal, the release of TRH is inhibited which reduces the release of TSH so blood thyroxine levels fall.
Identify and describe the stages of menstruation
Stage 1- Day 1 is when menstruation starts (the uterus lining breaks down and is released)
Stage 2- The uterus lining is repaired – from day 4 to day 14 – (becomes a spongey thick layer full of blood vessels ready for a fertilised egg.
Stage 3- An egg develops and is released from the ovary (ovulation) at about day 14
Stage 4- The lining is then maintained for about 14 days until the 28th. If no egg is planted in the uterus wall by the 28th day, the spongy lining breaks down and the cycle restarts.
Describe the role of the FSH (follicle stimulating hormone)
It is released by the pituitary gland and causes the a follicle (an egg and its surrounding cells) to mature in one of the ovaries. It also stimulates Oestrogen production.
Describe the role of Oestrogen
It is released by the ovaries and causes the lining of the ovaries to thicken and grow. A high level stimulates an LH surge.
Describe the role of LH
It is released by the pituitary gland and stimulates ovulation at day 14- the follicle ruptures and the egg is released.
It also stimulates the remains of the follicle to develop into a structure called corpus luteum which secretes progesterone.
Describe the role if progesterone
It is released by the corpus luteum after ovulation and it maintains the lining of the uterus.
It also inhibits the release of FSH and LH
When the level of FSH falls and there’s low oestrogen levels, the uterus lining breaks down.
A low progesterone level allows FSH to increase and then the whole cycle starts again.
How does clomifene therapy help treat infertility?
Some women are infertile because they don’t ovulate regularly so they take clomifene. This causes more LH and FSH to be released by the body which stimulate egg maturation and ovulation. By knowing when the female is ovulating, the couple can have intercourse during this time to increase the chance of pregnancy.
How does IVF help treat infertility?
IVF involves collecting a womans eggs and fertilising them in a lab. These are grown into embryos. Once they are tiny balls of cells, a few are transferred to the woman’s uterus to improve the chance of pregnancy.
FSH and LH are given before egg collection to stimulate egg production so they can collect more than one.
IVF is an example of ART
How can oestrogen be used as a contraceptive?
If the level of oestrogen is kept permanently high, it inhibits the production of FSH and after a while egg development and production stay stopped
How can progesterone be used to reduce fertility?
One way is by stimulating the production of thick cervical mucus which prevents any sperm from getting through the entrance to the uterus and reaching the egg.
Give 1 advantage of hormonal contraceptive methods
They are more effective at preventing pregnancy and there isn’t the hassle about worrying about contraceptives every time they have intercourse
Give 1 disadvantage of hormonal contraceptive methods
They can have unpleasant side effects like headaches and mood changes as well as not being defences against STIs
