Control in the body - Hormones Flashcards
What are hormones?
Chemical messengers which travel in the blood to activate target cells
How are hormones trasported?
They are carried in the blood plasma to other parts of the body
What sort of cells do hormones affect?
Target cells
What do hormones control?
Things in organs and cells than need constant adjustment
What are hormones produced and sectreted by?
Glands
How fast do hormones travel through the body?
At ‘the speed of blood’
What does the pituitary gland produce?
Many important hormones including FSH and LH
What do the ovaries produce?
Oestrogen
3 differences between the ways hormones and the nervous system
Nerves
- Very fast action
- Act for a very short time
- Act on a very precise area
Hormones
- Slower action
- Act for a long time
- Act in a more general way
Definition of the menstrual cycle
The monthly release of an egg from a woman’s ovaries, and the build-up and breakdown of the protective lining in the uterus (womb)
What happens on day 1-5 of the menstrual cycle?
The uterus lining breaks down. This is called menstration.
The pituitary gland releases FSH
What happens on day 5-14 of the menstrual cycle?
FSH causes an egg folicle inside the ovary to grow and mature.
Oestrogen is released from the egg follicle as it grows and matures
Oestrogen makes the pituitary gland stop FSH and start LH and causes the uterus lining to thicken
What happens on day 14 of the menstrual cycle?
LH levels peak and the egg is released from the follicle
LH stops Oestrogen release
The release of the egg is called ovulation
What happens day 14-21 of the menstrual cycle?
Progesterone is released by the empty follicle - this maintains the uterus lining and stops LH
What happens day 21-28 of the menstrual cycle?
If the egg is not fertilised then the levels of progesterone start to fall
The uterus lining will soon break down again
If the egg is fertilised the uterus wlining must ont break down (otherwise the fertilized egg will not develop)
Corpus luteum continues to produce progesterone
How does Oestrogen reduce fertility?
It prevents the release of an egg - if the oestrogen is taken every day to keep the level of it permanently high which inhibits the production of FSH - after a while egg development and production stop and say stopped
How does progesterone reduce fertility?
It stimulates the production of thick cervical mucus (which prevents any sperm getting thorugh and reaching the egg)
Pro’s of the combined pill?
- The pill’s over 99% effective at preventing pregnancy
- It reduces the risk of getting some types of cancer
Cons of the pill?
- It isn’t 100% effective
- It can cause side effects like headaches, nausea, irregular mestrual bleeding and fluid retention
- It doesn’t protect you against STD’s
A reason why some women can’t get pregnant
They have low FSH levels which mean the egg can’t meture - meaning no eggs are released and the woman can’t get preggers
How can fertility be increased?
By injecting hormones FSH and LH to stimulate egg release in their ovaries
Pro’s of increasing fertility?
It helps a lot of women to get pregnant when previously they couldn’t
Cons of increasing fertility?
It doesn’t always work, some women may have to do it many times - which can be expensive
Too many eggs could be stimulated, resulting in unexpected multiple births (21% of IVF babies are twins)
Pro of IVF?
It can give an infertile couple a child
