B3.2 The Endocrine System Flashcards
What are hormones?
Hormones are chemical messengers
Where are hormones produced?
They are produced in endocrine glands and are secreted into the blood.
Where in the blood do hormones travel in?
The blood transports the hormones in the plasma around the body
What do hormones control?
Hormones control body processes that need constant adjustment - such as body temperature
Define homeostasis
Maintaining a controlled internal environment
Name all the glands and the hormones they produce
thyroid gland produces thyroxine adrenal glands produces adrenaline Pancreas produce insulin and glucogen Reproductive glands: - ovaries produce oestrogen and progesterone - testes produce testosterone
What do the hypothalamus and pituitary gland produce?
These produce hormones that regulate production of other hormones
How do hormones travel to target organs?
Hormones diffuse out of the blood and bind to specific receptors for that hormone, found on membranes or in the cytoplasm of cells in the target organs, known as target cells. Once bound to their receptors the hormones stimulate the target cells to produce a response
Compares the nervous system to the endocrine system
The speed of communication for nerves is very fast whereas for hormones it is slower.
In the nervous system an electrical impulse travels along the axon of a neurone. In the endocrine system the hormones are transported in the blood.
The duration is response is short for nerves whereas for hormones it is long acting.
Nerves target a very precise area whereas hormones target a larger area
Where are the adrenal glands located?
The adrenal glands are located just above the kidneys
What does adrenaline do?
Adrenaline prepares the body for intensive action. It is called the ‘fight or flight’ response. They are secreted in times of stress.
It activates processes that increase the supply of oxygen and glucose to cells.
How do adrenaline prepare the body for ‘fight or flight’?
Adrenaline binds to specific receptors in the heart. This causes the heart muscle to contract more frequently and with more force, so heart rate and blood pressure is increased.
This 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. This causes the liver to break down its 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.
Where is the thyroid gland located?
In the neck
What is thyroxine for?
Thyroxine plays an important role in regulating metabolic rate
It controls how much energy is available to the cells.
How are thyroxine levels controlled?
When the body requires more energy, the hypothalamus causes the pituitary gland to releases thyroid-stimulating hormone (TSH). TSH stimulates the thyroid gland to release thyroxine. This increase the metabolic rate, allowing cells to transfer additional energy.
When cells have the required amount of energy, the hypothalamus inhibits TSH. The thyroid gland therefore stops releasing thyroxine.
Testosterone
Main sex hormone
Produced in the testes
Stimulates sperm production and is important for the development of the male reproductive system.
What is the menstrual cycle?
The menstrual cycle is a monthly cycle during which a woman’s body gets ready for pregnancy.
How long does the menstrual cycle last?
28 days
What happens in each stage of the menstruation cycle?
Day 1- The uterus lining breaks down and is released
From day 4 to day 14 the lining of uterus starts to thicken, to get ready to receive a fertilising egg.
About day 14 an egg develops and is released from an ovary. This is called ovulation.
The lining is then maintained for about 14 days, until day 28. If no fertilised egg has implanted into the uterus wall by day 28, the uterus lining starts to break down and then the whole cycle starts again.
How effective is the oestrogen and progesterone pill?
Over 99%
Ovary
Eggs mature here
Negative tropism
If a part of the plant grows away from the stimulus
cervix
entrance to uterus
vagina
Receives sperm from the penis during sexual intercourse
How effective is intrauterine device?
Over 99%
Oestrogen
made and secreted by the ovaries
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
Peaks between day 4 and day 14
Explain the commercial use of plant hormones:
Producing seedless fruits
Fruits normally grow on plants which have been pollinated by insects. If the plant doesn’t get pollinated, the fruit and seeds don’t grow.
If auxins and gibberellins are applied to the unpollinated flowers of some types of plant, the fruit will grow but the seeds won’t.
This produces parthenocarpio fruit- fruit without any seeds
How effective is condom (female)?
95%
LH
luteinising hormone
Released from the pituitary gland
Stimulates the release of an egg at day 14 (ovulation)
Indirectly stimulates progesterone production
Progesterone
Produced by the ovaries
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 levels allows FSH to increase and then the whole cycle starts again
If a fertilised ago implants in the uterus (i.e the woman becomes pregnant) then the progesterone level will stay high to maintain the uterus lining during pregnancy
The progesterone levels stay high between day 14 and day 28 to see if the egg is going to be fertilised or not
diaphragm or cervical cap
Non-hormonal
Inserted into the vagina to cover the cervix. Prevents sperm cells from entering the uterus
Removed after six or more house following sexual intercourse
Not effective unless used in combination with a spermicide
Define hormonal contraception
These use hormones to disrupt the normal female reproductive cycle.
Explain the commercial use of plant hormones:
Ripening fruit
Ethene is sprayed on fruit trees and plants so that their fruits ripen quicker. This allows fruit to be ready earlier in the growing season.
Progesterone pill
Hormonal
Involves the hormone progesterone
Thickens mucus from the cervix, stopping sperm from reaching an ovum
It also thins the lining of the uterus preventing implantation, and can prevent ovulation
Must be taken around the same time everyday
How effective is condom (male)?
98%
Describe the shoot’s phototropism
Shoots are positively phototropic
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 elongate (grow) faster on the shaded side, so the shoot bend towards the lights.
How effective is diaphragm and cap?
92% - 96%
How effective is the progesterone pill?
Over 99%
Define non-hormonal contraception
These are barrier methods that prevent a sperm contacting the egg or physical devices that release chemical compounds. These chemical kill sperm cells (spermicides) or prevent the implantation of fertilised eggs
Condom
Non-hormonal
Placed over the penis (male) or vagina (female). Prevents sperm entering the vagina.
Prevents sperm entering the vagina
Can also prevent the spread of sexually transmitted infections (STIs)
Phototropism
Growing towards the light
Explain the commercial use of plant hormones:
Controlling dormancy
Seeds remain dormant until conditions are ideal for growth. This normally prevents them germinating at the end of the summer so they survive the winter. Commercial growers trigger seeds to germinate in the winter by spraying them with gibberellins or auxins in the greenhouse. It also helps make sure all the seeds in a batch germinate at the same time.
‘Natural’ methods of contraception
Not having sexual intercourse is most fertile or withdrawal where the man pulls the penis out before ejeculation
Non-hormonal
intrauterine device (IUD, coil)
Non-hormonal
Inserted into the uterus
Releases copper, which prevents sperms surviving in the uterus and fallopian tubes
Can also prevent implantation of a fertilised ovum
remains effective for 5-10 years
oestrogen and progesterone pill (combined pill)
hormonal
Prevents ovulation
Thickens mucus from the cervix, stopping sperm from reaching an ovum
Prevents implantation of a fertilised egg onto the uterus wall
Taken daily for 21 days of the me trial cycle
Fallopian tube (oviduct)
where the egg is fertilised before travelling along the tube to the uterus
Explain the commercial use of plant hormones:
Delaying ripening
Auxin is sprayed on fruit trees to delay ripening. This allows a harvest to be collected all at the same time, and can prevent fruit from dropping off trees early.
Why are natural methods least effective in preventing pregnancy?
They rely on getting the timing exactly right
Describe the root’s phototropism
Roots are negatively phototropic
If a root starts being exposed to light, more auxin accumulates on the more shaded side. The auxin inhibits cell elongation on the shaded side so the root bends downwards, back into the ground
Cause of infertility
Blocked Fallopian tube
Blocked sperm ducts
Not enough sperm being produced in the testes
A lack of matured eggs produced in the ovaries
A failure of the ovaries to release an egg
Too low FSH levels to cause their eggs to mature
uterus (womb)
the foetus develops here
Fertility treatment
Infertility treated by hormones
FSH can be used as an artificial fertility drug. When the woman takes this drug it stimulates eggs to mature in her ovaries. It also triggers oestrogen production. This significantly increases her chances of getting pregnant as it increases the likelihood of one or more eggs being released
How does IVF work?
IVF stands for in vitro fertilisation
If treatment with hormones alone is not successful people may use IVF.
This technique involves doctors collecting eggs from the ovary of the mother and fertilising them with sperm from the father outside the body. FSH and LH are given to the mother to ensure that as many eggs in her ovaries mature as possible and are harvested.
As female age increases, the success rate for IVF treatment…
decreases
Describe the root’s gravitropism
Roots are positively gravitropic
A root growing sideways will have more auxin on its lower side
The auxins will inhibit growth on the lower side which means the cells at the top will elongate faster so the root will bend downwards.
What are the considerations around IVF treatment?
It is not a natural process
It allows parents to conceive who would otherwise not be able to have a baby
It enables older parent to have children though they can find the demands of bringing up a child challenging
Many IVF treatments results in multiple births. This can be dangerous for both mother and the unborn babies
IVF treatment is very expensive. There is only limited availability through the National Health Service (NHS)
It allows younger women’s to focus on their careers, and choose to have a baby later in life.
Define tropism
When plants detect stimuli in their environment, and can respond by growth in a particular direction which is called tropism.
Positive tropism
If a part of a plant grows towards a stimulus
How can you investigate the effect of light on the growth of cress seeds?
Put 10 cress seeds into three different Petri dishes, each lined with moist filter paper.
Shine a light into one of the dishes from above and two of the dishes from different directions
Leave your cress seeds alone for one week until you can observe their response
You will find the seeds growing towards the light
Control variables- temperature, distance from lamp, type of seeds, number of seeds
Ethane effect on fruits
Causes plants fruits to ripen by stimulating the conversion of starch into sugar. This is why a ripe fruit tastes sweeter than an unrepentant one. It is the only plant hormone that exists as a gas.
Ethene stimulates enzymes that causes fruit to ripen
Ethene is produced by aging leaves. It stimulates the cells that connect the leaf to the rest of the plant to expand. This breaks the cell walls and causes the leaf to fall of the plant.
How effective is the intrauterine system?
Over 99%
Gibberellins
They promote growth, particularly stem elongation. They can also end the democracy period of seeds and buds. This leads to shoots and flowers opening.
Stimulates seed germination, stem growth and flowering
Gravitopism
Growing in the same direction as gravity
Explain the commercial use of plant hormones:
Killing weeds
Many weed killers contain auxins. Weed killers are eclecticism herbicides. They kill weeds that are broad-leaved plants (dicotyledons) but do not affect narrow leaf plants (monocotyledons eg. Grass). The auxin weed killer makes the weeds grow too fast. This rapid uncontrolled growth kills the plant.
Intrauterine system (IUS, hormonal coil)
hormonal
Inserted into the uterus
Has the same effect on the body as the progesterone-only pill
Remains effective for 3-5 years
FSH
Follicle stimulating hormone Secreted by the pituitary gland Causes an egg to mature Stimulates the ovaries to produce oestrogen Peak on day 14
Describe the shoot’s gravitopism
Shoots are negatively gravitropic
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.
Explain the commercial use of plant hormones:
Promoting root growth
Rooting powder contains auxins. Horticulturists and gardeners use auxin to produce identical plants, or clone, from cuttings. They cut off a plant shoot, dip it into rooting powder and plant it. After a few days roots develop from the cut stem. The new roots anchor into the soil and take up water and minerals.
Auxins
They are plant hormones that enables a plant to grow towards or away from a stimulus
They move through the plant in solution
They are produced in the tips and diffuses backwards to stimulate the cell elongation process which occurs in the cells just behind the tips.
They promote growth in shoots and inhibit growth in roots
Sterilisation contraceptive method
Non-hormonal
Involves a surgical procedure to cut or tie tubes in the reproductive system.
In women, the procedure means eggs are prevented from traveling from the ovaries to the uterus
In men, it prevents sperm from being ejaculated
Over 99% effective
IVF is not reliable. What can it result in?
no pregnancy
multiple pregnancies
Which contraceptive methods involve the hormone progesterone?
Injection-effective for up to 3 months;does what a mini pill does Implant-inserted beneath the skin of the arm;effective for 3 years;does what a mini pill does Intrauterine system (IUS)-a T-shape piece of plastic inserted into the uterus. Effective for 3-5 years Mini-pill- has to be taken everyday
