B10 Animal and Plant Hormones Flashcards
What happens in stage one of the menstrual cycle?
Menstruation- the lining of the uterus breaks down for about 4 days
Between which days does the uterus lining build back up?
From day 4-14
What occurs in the third stage and when?
An egg is released from the ovary at day 14.
For how long is the wall of the uterus maintained?
14 days, until around day 28
What happens to the uterus wall if no fertilised egg has been received?
The spongy lining breaks down.
What 2 things does follicle-stimulating hormone do?
- Trigger maturation of an egg in an ovarian follicle
- Stimulates the ovaries to produce oestrogen
What does luteinising hormone do?
Stimulates the release of an egg
What 3 things does oestrogen do?
- Causes uterus lining to grow/maintains it
- Inhibits FSH release
- Stimulates LH release
What 2 things does progesterone do?
- Maintains the uterus lining
- Inhibits LH and FSH
The falling level of which hormone causes the uterus lining to break down?
Progesterone
Why can oestrogen be used as a contraceptive?
Maintaining high oestrogen levels inhibits FSH, so egg maturation and therefore egg release will stop.
Why can progesterone be used as a contraceptive?
- Stimulates the production of thick mucus in the cervix which acts as a barrier
- Inhibits egg maturation and release
Which contraceptive pill has the least side effects?
progesterone-only
List 2 benefits of the oral contraceptive pill:
- 99% efficacy
- Reduces risk of some cancers
List 2 disadvantages of the pill:
- Doesn’t protect against STDs
- Side effects- headaches, nausea
What is a contraceptive patch?
A small patch containing oestrogen and progesterone that is stuck to the skin
What is a contraceptive implant?
An implant inserted under the skin that releases progesterone
What is a contraceptive injection?
An injection containing progesterone
What is used with a diaphragm to increase its efficacy?
Spermicide
Where is a diaphragm fitted?
Over the cervix
What are the two types of IUDs?
- Hormonal IUDs- release progesterone
- Copper IUDs- make uterus inhabitable for sperm
List 2 problems with fertility drugs
- Not always effective
- Excessive stimulation of eggs could lead to unexpected multiple pregnancies
What does IVF stand for?
In vitro fertilisation
What steps does IVF entail?
- Woman given FSH and LH
- Eggs collected from ovaries
- Eggs fertilised in lab with sperm
- Fertilised eggs grow into embryos in an incubator
- Once formed, 1 or 2 embryos are transferred to the uterus
List 3 disadvantages of IVF:
- Low success rate (26% in the UK)
- Hormone side effects (abdominal pain, vomiting, dehydration)
- Can lead to multiple births, which are riskier
Name 2 social and ethical issues regarding IVF:
- Unused embryos are destroyed- killing potential lives
- Genetic testing before implantation causes concern for selection based on certain characteristics
Which gland releases TSH?
The pituitary gland
What does thyroxine regulate?
Basal metabolic rate
How is thyroxine level controlled?
By a negative feedback system
Where are the adrenal glands found?
Above the kidneys
When is adrenaline released?
In response to stress or fear
How does adrenaline increase the supply of oxygen and glucose to cells?
By increasing your heart rate
What does auxin control in plants?
Phototropism and geotropism
Where is auxin produced?
The tips of roots and shoots
Where do auxins tend to accumulate?
On the shaded and lower sides
Explain what will happen in terms of growth to a shoot with a light source on its right hand side:
The auxins will accumulate on the left hand side as they move away from light. They will stimulate growth on this side, causing the cells on the left side to elongate faster than the right. This imbalance will cause the shoot to curve towards the source.
How do shoots grow relative to gravity?
In the opposite direction- they are negatively geotropic
Explain what will happen to shoot growing sideways in terms of growth:
The auxin will accumulate on the lower side of the shoot due to gravity, causing the cells on the lower side to elongate faster than on top. The shoot will end up pointing upwards.
Auxin […] root growth.
Inhibits
Why do some selective weed-killers contain auxin?
It disrupts the growth patterns of broad-leaved weeds, killing them.
How can auxin be used to grow plants from cuttings?
You can add rooting powder (containing auxins), which stimulates the growth of roots from the cutting.
What type of plant hormones stimulate seed germination?
Gibberellins
List 3 uses of gibberellins:
- Controlling dormancy- plants grow at any time and at same time
- Inducing flowering
- Growing larger fruit
What gas is produced by aging parts of a plant?
Ethene
What is the role of ethene?
- Controls cell division
- Stimulates enzymes that ripen fruit
How is ethene used commercially?
To speed up the ripening of fruit, so that it can be picked whilst still unripe
Define ovulation
The release of an egg from the ovary
Define phototropism
The growth of a plant in response to light
Define geotropism
The growth of a plant in response to gravity
Define dormancy
When a seed is temporarily unable to germinate even when conditions are favourable
