B3.2 Flashcards
what are the target cells
target cells are cells with the specific receptor for a hormone that produce an effect when the hormones binds
what are hormones
hormones are chemical messengers that are secreted by glands of the endocrine system into the bloodstream
what does the hormone thyroxine control in the body
thyroxine controls metabolic rate
describe thyroxine as a negative feedback system
when the level of thyroxine decreases the pituitary gland produces thyroid stimulating hormone which causes the thyroid gland to produce more thyroxine
When the level of thyroxine increases, the pituitary gland produces less TSH
when is adrenaline secreted
during times of anxiety, fear or stress
give 3 effects of adrenaline in the body
increases heart and birthing rate
increases blood glucose concentration
dilates the pupils
what does oestrogen do
oestrogen causes the uterus lining to thicken
what hormones does oestrogen inhibit?
oestrogen inhibits follicle stimulating hormones(FSH)
what does progesterone do
maintains the womb lining
what hormone does progesterone inhibit
progesterone inhibits FSH
what does FSH do?
FSH stimulates the follicle to mature and release oestrogen
what does LH do
a surge in LH causes the release of an egg from a follicle (ovulation)
how do oestrogen pills work to prevent pregnancy
oestrogen pills inhibit FSH which stops the egg from maturing
how do progesterone pills work to prevent pregnancy
progesterone pills cause a sticky mucus to form at the cervix which prevents the sperm from fertilising the egg
give one advantage and one disadvantage of hormonal contraception (e.g. the pill)
advantage - more than 99% effective
disadvantage - it can cause side effects like weight gain
give one advantage and one disadvantage of condoms as non-hormonal contraception
advantage - 98% effective and prevents from STDs
disadvantage - condoms are only one time use and they can break
describe how IVF is carried out
the mother is given FSH
sperm from the father and eggs from the mother are collected
the egg is fertilised in a laboratory and allowed to develop into an embryo
the embryo is then put into the mother’s uterus
what hormone is given in female fertility drugs
FSH
what does auxin trigger?
auxin triggers growth of the main stem of the plant ( and it inhibits the growth of side shoots)
what is phototropism and which part of a plant is positively phototropic?
phototropism is the growth of a plant towards a light source. the shoots are positively phototropic ( they grow towards the light source)
what is geotropism and which part of a plant is positively geotropic?
geotropism is the growth of a plant towards the pull of gravity. the roots are positively geotropic (they grow down in the same direction as the pull of gravity)
how does auxin cause the shoots to grow towards the light source?
auxin collects on the shaded side
promotes cell growth
shoot curves towards the light
what do gibberellins do
promote seed germination
increase the length between stem nodes
delays leaf shedding
what does ethene cause when it is applied to plants?
it causes fruit ripening which is useful so that fruit can be transported long distances
how do selective weedkillers work
they contain auxin
they work on some plants (weeds) and not others
they cause the plant to grow too quickly which kills it
what are parthenocarpic fruit
seedless fruit
