B3.2 - Hormones, Edocrine System, Menstrual Cycle Flashcards
What is the menstrual cycle
The menstrual cycle is the monthly sequence of events in which the female body releases an egg and prepares the uterus (womb) in case it receives a fertilised egg
What happens on day 1 in the menstrual cycle
The uterus lining breaks down and is released
What happens from day 4 to 14 in the menstrual cycle
The lining of the uterus builds up again into a thick spongy layer full of blood vessels ready to receive a fertilised egg
What happens at day 14 in the menstrual cycle
An egg develops and is released from an ovary (ovulation)
What happens from day 14 to 28 in the menstrual cycle
The lining of the uterus is maintained. If no fertilised egg has planted into the uterus wall by day 28, the spongy lining starts to break down again and the whole cycle starts over
Where is FSH and LH released, and what do they do
FSH and LH are released from the pituitary gland in the brain. They help to control the menstrual cycle
Where is progesterone produced and what does it do
It is produced in the ovaries. It helps to support pregnancy and is involved in the menstrual cycle
Where is oestrogen prod fed and what does it do
It is produced in the ovaries. It’s involved in the menstrual cycle and promotes female sexual characteristics. Oestrogen is the main female sex hormone
Where is testosterone produced and what does it do
It is produced in the testes. It stimulates sperm production and is important for the development of the male reproductive system. Testosterone is the main male sex hormone
The menstrual cycle is controlled by 4 hormones. What does FSH do?
Causes an egg to mature in one of the ovaries.
Stimulates the ovaries to produce oestrogen.
The menstrual cycle is controlled by 4 hormones. What does oestrogen do?
Causes the lining of the uterus to thicken and grow.
Stimulates the production of LH
Inhibits the production of FSH so that only one egg is released in each cycle.
The menstrual cycle is controlled by 4 hormones. What does progesterone do?
Maintains the lining of the uterus. When the level of progesterone falls and there’s a low oestrogen level, the lining breaks down.
Inhibits the production of FSH and LH.
A low progesterone level allows FSH to increase and then the whole cycle starts again.
The menstrual cycle is controlled by 4 hormones. What does LH do?
Stimulates the release of an egg at day 14 (ovulation).
Indirectly stimulates progesterone production.
What are hormones
Hormones are chemicals produced in various glands called endocrine glands. These glands make up your endocrine system
How do hormones travel and where are they released
Hormones are released directly into the blood. The blood then carries them to other parts of the body. They travel all over the body but they only affect particular cells in particular places
What do target cells have
They have the right receptors to respond to that hormone
What is adrenaline
A hormone released by the adrenal glands
What does adrenaline prepare the body for
Adrenaline prepares the body for ‘fight or flight’
Fill in the gaps
Hormones are ______ compared to nervous impulses but they have _______ lasting effects
Slower
Longer
Adrenaline binds to specific receptors in the heart which causes…..
The heart muscle to contract more frequently and with more force so heart rate and blood pressure increase. The increases blood flow to the muscles, so the cells receive more oxygen and glucose for increased respiration
Adrenaline also binds to receptors in the liver which causes…..
The liver to break down it’s glycogen stores to release glucose. This increases the blood glucose level so there’s more glucose in the blood to be transported to the cells
What happens when you brain detects a stressful situation
The brain sends nervous impulses to the adrenal glands which respond by secreting adrenaline. This gets the body ready for action
How can your body control the levels of hormones in the blood
By using negative feedback systems
What is negative feedback systems
When the body detects that the level of a substance has gone above or below the normal level it triggers a response to being the level back to normal again
What is thyroxine and what is it made from
Thyroxine is a hormone released by the thyroid gland (found in the neck). Thyroxine is made in the thyroid gland from iodine and amino acids
What is the role of thyroxine
It regulates metabolic rate (or metabolism) - the speed at which chemical reactions in the body occur. It’s important for loads of processes in the cosy such as growth and protein synthesis
Thyroxine is realised in response to…
Thyroid stimulating hormone which is released from the pituitary gland
What does a negative feedback system do in terms of thyroxine
It keeps the amount of thyroxine in the blood at the right level
What happens if a fertilised egg implants in the uterus (I.e. the women become pregnant)
The progesterone level will stay high to maintain the uterus lining during pregnancy
What does it mean if a person is infertile
They can’t reproduce naturally
Some women have levels of FSH that are too low to cause their eggs to mature. This means….
No ovulation takes place (no eggs are released) and the women can’t get pregnant
The hormones FSH and LH can be injected to….
Stimulate ovulation
What does IVF involve
Collecting eggs from the women’s ovaries and fertilising them in a lab using the mans sperm. These are then grown into embryos.
What happens once the embryos are tiny balls of cells
Or or two of these calls are transferred to the women’s uterus to improve the chance of pregnancy
Why are FSH and LH give before egg collection
To stimulate egg production (so that more than one egg can be collected)
Why are contraceptives used
To prevent pregnancy
How does the hormone progesterone work
- stimulates the production of thick cervical mucus, making it less likely that any sperm will get through and reach an egg
- thins the lining of the uterus to reduce the change of a fertilised egg implanting
- prevents ovulation by inhibiting the products of FSH and LH
Which hormone does the INJECTION use and how effective is it
The INJECTION uses progesterone and it is effective for up to 3 months and more than 99% effective
Which hormone does the IMPLANT use, how is it used, and how effective is it
The IMPLANT uses progesterone, it is inserted beneath the skin of the arm and is effective for 3 years and more than 99% effective
Which hormone does IUS use, what is it, and how effective is it
IUS uses progesterone, it is a T shaped piece of plastic inserted into the uterus and is effective for 3-5 years and more than 99% effective
What hormone does the mini pill use, and how many times does it have to be taken
The MINI PILL uses progesterone and it had to be taken every day
It is more than 99% effective
How does oestrogen prevent ovulation
By inhibiting FSH
What hormone does the COMBINED PILL use and how is it taken
The COMBINED PILL uses progesterone and oestrogen and it is taken in a 21 day pill 7 days no pill cycle
It is more than 99% effective
What hormone does the PATCH use and how is it worn
The PATCH uses progesterone and oestrogen and is worn on the skin in a 4 week cycle (replaces once a week for 3 weeks then no patch worn for a week)
It is more than 99% effective
What is a barrier method and what are some examples
A barrier method tries to stop the egg and speed meeting. Some examples include a
•condom
•female condom
•diaphragm
How effective is a condom and how is it used
A condom is 98% effective and is worn over the penis during intercourse to prevent sperm entering the vagina
How effective is a female condom and how is it used
A female condone is 95% effective and is worn inside the vagina during intercourse
How effective give is a diaphragm, how is it used, and how is it fitted
A diaphragm is 92-96% effective and fits over the cervix to stop sperm from meeting the egg. Has to be fitted by a GP/nurse the first time it’s used and has to be used with a spermicide
What is an IUD, how is it used how effective is it
IUDs are T shaped devices that contain copper. They’re inserted into the uterus and prevent sperm from surviving. They also alter the lining of the womb so that fertilised eggs can’t implant. They’re more than 99% effective and can be kept in for up to 10 years
What does sterilisation involve and how effective is it
Sterilisation involves a surgical procedure to cut or tie tubes in the reproductive system. In women the procedure means eggs are prevented from travelling from the overuse to the uterus. In men it prevents sleek from being ejaculated. The methods are over 99% effective
Why might side effects be a con (disadvantage) for contraception
Hormonal methods can have unpleasant side effects e.g. heavy or irregular periods, acne, headaches, mood changes
Why might medical input be a con (disadvantage) for contraception
Many methods involve at least one trip to a nurse or doctor and people may feel uncomfortable about the procedures involved. However these methods tend to be more effective than barrier or natural methods
Why might length of action be a pro (advantage) for contraception
Long lasting methods may be preferable over having to think about contraception every day or every time intercourse is on the cards
What are natural methods and how effective are they
Natural methods refer to just not having sexual intercourse when the women is most fertile or withdrawal. These methods are the least effective at preventing pregnancy as they rely on getting the timing exactly right
Why is possibility of doing it wrong a con (disadvantage) of contraception
Barrier methods and natural methods have to be done properly each time a couple have intercourse. The same is true with some hormonal methods for example if a woman doesn’t take her pills correctly the methods won’t work properly
Why might sexually transmitted infections (STIs) be a con (disadvantage) to contraception
These are infections that are passed from person to person during sexual intercourse. the only method of contraception that can protect against them is condoms
What are auxins
Auxins are plant hormones which control growth at the tips of shoots and roots. They move through the plant in solution
Where is auxin produced and what does auxin promote
Auxin is produced in the tops and
diffuses backwards to stimulate the cell elongation process which occurs in the cells just behind the tips.
Auxin promotes growth in the shoot but actually inhibits growth in the root
What are auxins involved in
Auxins are involved in the growth responses of plants to light (phototropism) and gravity (gravitropism)
What happens when a shoot tip is exposed to light
It accumulates more auxin on the side that’s in the shade than the side that’s in the light. This makes the cells grow (elongate) faster on the shaded side so the shoot bends towards the light
Shoots are positively phototropic. What does this mean
The shoots will grow towards light
Shoots are negatively gravitropic. What does this mean
The shoots will grow away from gravity
What does it mean when a shoot is growing sideways
Gravity produces an unequal distribution of auxin in the tip with more auxin on the lower side. This causes the lower side to grow faster, bending the shoot upwards
Roots are positively gravitropic. What does this mean
The root will grow towards gravity
Roots are negatively phototropic. What does this mean
The roots grow away from light
A root sideways means that
It will have more auxin on its lower side
In a root the extra auxin inhibits growth. This means
The cells on top elongate faster and the root bends downwards
What happened if a root starts being exposed to some light
More auxin accumulates on he more shaded side
The auxin inhibits cell elongation on the shaded side which means
The root bends downwards back into the ground
What is gibberellin and what does it stimulate
Gibberellin is a type of plant growth hormone
It stimulates seed germination, stem growth and flowering
It stimulates the stems of plants to grow by stem elongation - this helps plants to grow tall
Gibberellin stimulates plant stems to grow
What is ethene produced by and what does it stimulate
Ethene is produced by aging leaves. It stimulates shedding of leaves. It also stimulates enzymes that cause fruit to ripen
What do auxins inhibit, what are they produced by
Auxins inhibit the shedding of leaves and auxins are produced by young leaves. As the leaves get older, they produce less auxin leading to leaf loss
Plant hormones can be used as selective herbicides (weedkillers). Explain which hormone is used and how it is used as a weed killer
Selective herbicides have been developed using auxins which only affect the broad leaved plants. They totally disrupt their normal growth patterns which soon kills them, whilst leaving the grass and crops untouched
Plant hormones can be used as growing from cuttings with rooting powder. Explain which hormone is used and how it is used as growing from cuttings with rooting powder
Normally if you stick cuttings in the soil they won’t grow but if you add rooting powder (with contains auxins) they will produce roots rapidly and start growing as new plants. This enables growers to produce lots of clones of a really good plant very quickly
Plant hormones can be used to produce seedless fruit. Explain which hormones are used and how it is used to produce seedless fruit
If auxins and gibberellins are applied to unpollinated flowers of some types of plant, the fruit will grow but the seeds won’t. This produces fruit without seeds
Plant hormones can be used to control dormancy. Explain which hormone is used and how it is used to control dormancy
Seeds can be treated with gibberellin to alter dormancy and make them germinate at times of year that they wouldn’t normally. It also helps to make sure all the seeds in a batch germinate at the same time
