Biological Control of Fertility Flashcards
Give 4 examples of factors which can affect a person’s fertility?
weight
stress
disease
pollutants e.g. cigarette smoke
What are the 2 types of fertility?
Continuous
Cyclical
What do men have the potential to father?
a child from puberty onwards due to the negative feedback effect of testosterone
What does the negative feedback effect of testosterone maintain?
a constant level of the pituitary hormones FSH and ICSH in the bloodstream, resulting in the steady release of testosterone
What does the steady release of testosterone cause?
sperm to be continually produced in the testes , resulting in men being fertile throughout their lives.
When do women only release eggs?
from puberty until they reach the menopause
What is the menopause?
when ova are no longer released from the ovaries and menstruation no longer occurs.
In most women when does menopause occur?
45-55
When can a woman fall pregnant?
Each month there is only a limited number of days either side of ovulation
What does the interaction of the pituitary and ovarian hormones result in?
the period of fertility in females only lasting for 1-2/3-4 days
What is a woman’s fertility?
cyclical
What are the 2 main indicators that can be used to calculate a woman’s fertile period?
body temperature
consistency of cervical mucus
Why are the 2 indicators useful?
as they can be used to predict when a woman will ovulate and therefore when she is most likely to fall pregnant.
What is the method of fertility by using the indicators to predict when a woman will ovulate and therefore when she is most likely to fall pregnant called?
rhythm method
What are the processes of menstruation and ovulation are separated by?
intervals of about 2 weeks
Roughly 1 day after the surge in LH in the bloodstream that triggers ovulation, what happens to a woman’s body temperature?
rises by about 0.2-0.5’c
What happens after the body temperature rises?
it remains at this level for the duration of the luteal phase of the menstrual cycle
How long does the period of fertility last for?
about 1-2 days (after ovulation)
After a third daily recording of this increased body temperature what happens to the period of infertility?
the period of fertility is resumed as the unfertilised egg will have disintegrated
What happens to the cervical mucus during the fertile period?
the cervical mucus is secreted into the vagina
Describe the consistency of cervical mucus during the fertile period?
thinner, slippery and stretchy to allow sperm easy access to the female reproductive system
Why does the consistency of cervical mucus change during the fertile period?
due to the increasing oestrogen levels in the follicular phase
What happens to the consistency of cervical mucus after ovulation?
the mucus gradually increases in viscosity under the action of progesterone, showing that the system has returned to the infertile phase
What has the advancement of modern medicine allowed?
the development of a number of methods which can be used to overcome infertility
Give 4 examples of treatments used to help overcome infertility
stimulating ovulation
artificial insemination
IVF
ICSI
Why might a woman fail to ovulate?
failure of pituitary gland to secrete enough FSH or LH
If a woman fails to ovulate due to the failure of pituitary gland to secrete enough FSH or LH. How can ovulation be successfully stimulated?
by drugs that prevent the negative feedback effect of oestrogen on FSH secretion.
drugs that mimic the normal action of FSH and LH
What can ovulation stimulating drugs cause?
‘super-ovulation’ that can result in multiple births or be used to collect ova for IVF programmes
What is artificial insemination?
the insertion of semen into the female reproductive tract by some other means than sexual intercourse
Why might artificial insemination be used?
if a man has a low sperm count - several samples of his semen can be collected over a period of time and each preserved by freezing . They are defrosted and released into the female’s cerivical region at a time when she is most likely to be fertile.
if Donor semen is required - if the male is sterile, healthy semen samples may be obtained from a donor
What is the problem of infertility caused by which results in the use of IVF?
A blockage of the oviducts