Unit 2 KA3 - biology of controlling fertillity

Question 1

compare men and women’s fertile periods and describe why

Answer 1

men are continuously fertile due to the negative feedback control of testosterone maintaining a constant level of pituitary hormones FSH and ICSH in the bloodstreams so sperm are continuously being made
whereas women show cyclical fertility, meaning they are only fertile for a short period of time due to the changes in hormones in the menstrual cycle.

Question 2

what indicates the female fertile period? explain why

Answer 2

temperature rise - after the LH surge triggers ovulation the women’s body temp. increases by about 0.5 degrees Celcius.
thin watery cervical mucus - this allows easier access for sperm

Question 3

after ovulation, the mucus increases in ………..(due to the action of ……….) showing the ………… period is resumed.

Answer 3

viscosity, progesterone, infertile

Question 4

name the treatments for infertility

Answer 4

stimulating ovulation, artificial insemination, intracytoplasmic sperm injection (ICSI), or in vitro fertilisation (IVF)

Question 5

how is ovulation stimulated to treat infertility?

Answer 5

1 - drugs that mimic the normal action of FSH and LH

2 - drugs that prevent negative feedback of oestrogen on FSH secretion during the luteal pahse

Question 6

what is artificial insemination? describe the process

Answer 6

the introduction of semen into the female reproductive tract by some other means than sexual intercourse
several samples of the man’s semen are collected and frozen until required and are then defrosted and released into the female’s cervix during her fertile period.

Question 7

what is intracytoplasmic sperm injection? (ICSI)

Answer 7

when the head of a sperm is drawn into a syringe needle and injected into an egg to achieve fertilisation

Question 8

when is ICSI carried out?

Answer 8

if the male’s sperm are defective or low in number

Question 9

what is in vitro fertilisation? (IVF)

Answer 9

fertilisation that occurs outside the body in a culture dish

Question 10

why is IVF carried out?

Answer 10

to solve infertility caused by a blockage of the oviducts.

Question 11

describe the steps of IVF

Answer 11

1 - woman is given hormonal treatment to stimulate superovulation
2 - surgery to remove eggs
3 - eggs mixed with sperm in a culture dish of nutrient medium to allow fertilisation to occur
4 - fertilised eggs are incubated until they have formed at least 8 cells
5 - the embryos are then transferred to the uterus for implantation

Question 12

……………. can be carried out during IVF treatment to allow identification of ……………. and …………….

Answer 12

preimplantation genetic diagnosis (PGD) chromosomal abnormalities, gene disorders

Question 13

name the physical contraception methods and give examples

Answer 13

barrier method (condom, diaphragm), non-barrier method (intra-uterine device), or sterilisation (vasectomy, tubal ligation)

Question 14

name the chemical contraception methods and explain how they work

Answer 14

1 - pills: contain synthetic progesterone and oestrogen
increase the concentration of progesterone and oestrogen in the bloodstream to mimic negative feedback control so that; FSH and LH are inhibited from pituitary gland, follicle maturation is inhibited and ovulation fails to occur
2 - ‘morning after’ pills: emergency hormonal contraception which contains high doses of P and O
3 - mini pills: contains synthetic progesterone to thicken cervical mucus to reduce sperm access to the uterus