b5 homeostatis Flashcards
(156 cards)
1
Q
what do cells in the body need to survive?
A
a constant temperature and pH. and a constant supple of water and dissolved minerals
2
Q
how are the conditions in the body controlled and regulated?
A
the body has control systems that constantly monitor and adjust the composition of the blood and tissues
3
Q
what do the control systems include?
A
receptors which sense changes and effectors which bring about changes
4
Q
what is homeostasis?
A
the regulations of internal conditions or a cell or organism to maintain optimal conditions for function in response to internal and external changes
5
Q
what does homeostasis maintain the optimum conditions for?
A
- blood glucose concentrations
- temperatures
- water levels
6
Q
what types of responses can automatic control systems have?
A
- nervous responses
- chemical responses
7
Q
what components do all control systems have?
A
1) receptors- detect stimuli
2) co ordination centres- receive and process information from the receptors
3) effectors- bring about responses to restore optimal condition levels
8
Q
what does the nervous system enable for humans to do?
A
react to their surroundings and co ordinate their behaviour
9
Q
what are the components of the nervous system (in order)?
A
1) stimulus
2) receptor
3) co ordinator
4) effector
5) response
10
Q
how does the nervouus system work?
A
Information from receptors passes the neurones as electrical impulses to the central nervous system (CNS). The CNS. The CNS coordinates the response of effectors by sending electrical impulses to the motor neurones, leading to muscles contracting or glands secreting hormones in response to the stimuli
11
Q
what are the CNSes ?
A
in vertebrates, it is the brain and spinal chord
12
Q
what are the CNSes connected to?
A
sensory neurones and motor neurones
13
Q
what do sensory neurones do?
A
carry the information as electrical impulses from the receptors to the CNS
14
Q
what do motor neurones do?
A
carry electrical impulses from the CNS to the effectors
15
Q
what are effectors and what do they do?
A
they can be muscles or glands, they respond to nervous impulses from the CNS and bring about a change
16
Q
what are some different types of receptors?
A
taste receptors, light receptors and sound receptors
17
Q
what do synapses do?
A
they connect neurones , the nerve signal is transferred by chemicals which diffuse across the gap, these chemicals then set off a new electrical signal to the next neurone
18
Q
what are reflexes?
A
rapid, automatic responses to certain stimuli that dont involve the conscious part of the brain. they can reduce the chances of being injured
19
Q
examples of reflexes?
A
- if someone shines a bright light in your eyes, the pupils automatically get smaller so less light gets into the eye
- if you get a shock, your body releases the hormone adrenaline automatically
20
Q
what is a relay neurone?
A
it carries impulses within the CNS
21
Q
where do neurones in reflex arcs go through?
A
the spinal cord or the unconscious part of the brain
22
Q
what is the brain?
A
it controls our behaviour and is made of billions of interconnected neurones. it has different regions which carry out different functions
23
Q
what is the function of the cerebral cortex?
A
responsible for:
- consciousness
- intelligence
- memory
- language
24
Q
what is the function of the medulla?
A
controls unconscious activities such as:
- breathing
-heartbeat
25
what is the function of the cerebellum?
responsible for muscle co odrination
26
what are some methods that scientists use to study the brain?
1) studying patients with brain damage
2) electrically stimulating the brain
3) MRI scans
27
why do scientists study patients with brain damage?
because the effect of a damaged part of the brain can tell you a lot about what it does. for example, if an area at the back of the brain was damaged and the patient went blind, you know that area has something to do with vision
28
why do scientists electrically stimulate the brain to study it?
because the brain can be stimulated electrically by pushing a tiny electrode into a tissue and giving it a small zap of electricity. scientists can then observe what stimulating the different parts of the brain actually does to get a possible idea of their functions
29
why do scientists use MRI scans to study the brain?
it can produce very detailed pictures of the brain's structures. scientists can use it to find out which parts of the brain are active when people are doing things like recalling a memory or listening to music
30
what are some advantages to studying the brain?
knowledge of how the brain works has led to the development of treatments for disorders of the nervous system. eg: electrical stimulation can help reduce muscle tremors caused by nervous system disorders such as parkinson's disease
31
what are some of the downsides of scientists trying to study the brain?
the brain is incredibly complex and delicate, therefore the investigation of any treatment of the brain or disease is difficult. it also carries risks such as physical damage to the brain or increased problems with brain function
32
what is the sclera and its function?
its the tough, supporting wall of the eye. it protects the eye from injury
33
what is the cornea and its function?
its the transparent outer layer found at the front of the eye. it refracts light into the eye
34
what is the iris and it's function?
iris controls how much light enters the eye. it contains muscles that contract and relax that control the diameter of the pupil
35
what is the lens and its function?
it focuses the light into the retina (which contains receptor cells sensitive to light intensity and colour)
36
what are the ciliary muscles and suspensory ligaments?
they control the shape of the lens
37
what is the optic nerve and its function?
its a nerve which carries impulses from the receptors on the retina to the brain
38
how does the iris reflex to adjust for bright light?
when light receptors detect very bright light, a reflex is triggered which makes the pupils smaller. the circular muscles in the iris contract and the radial muscles relax. this decreases the diameter of the pupil and decreases the amount of light which can enter the eye
39
how does the iris reflex adjust for dim lighting?
when light receptors detect very dim lighting, a reflex is triggered which makes the pupils bigger. the radial muscles contract and the circular muscles relax. this increases the diameter of the pupil and increases the amount of light that can enter the eye
40
what can damage the retina?
bright light
41
what is accomodation?
when the eye focuses light onn the retina by changing the shape of the lens
42
what happens to the eye when you focus on a nearby object?
1) the ciliary muscles contract which slackens the suspensory ligaments
2) the lens becomes more fat
3) this increases the amount by which it refracts light
43
why do some people need reading glasses as they get older?
the lens loses its flexibility so it cannot spring back to its round shape, therefore light cant be focused well for near viewing
44
what happens to the eye when you look at a distant object?
1) ciliary muscles relax which allows the suspensory ligaments to pull tight
2) this makes the lens go thin
3) so it refracts light by a smaller amount
45
what causes long-sightedness?
1) this occurs when the lens is the wrong shape and doesnt refract light enough or the eyeball is too short.
2) the images are bought into focus behind the retina.
46
which type of glasses lens can fix long- sightedness?
convex lens (it curves outward).
it refracts light more so the light rays focus on the retina
47
what is the medical term for long- sightedness?
hyperopia
48
what causes short- sightedness?
1) the lens is the wrong shape and refracts the light too much, or the eyeball is too long.
2) the images of distant objects are bought into focus infront of the retina
49
what glasses lenses can fix short- sightedness
concave lenses which curves inwards so the light rays refract less and focus on the retina
50
what is the medical term for short- sightedness?
myopia
51
a) what are contact lenses?
b) advantages?
c) 2 different types?
a) they are thin lenses that sit on the surface of the eye and are shaped to compensate for the fault in focusing
b) they're lightweight, almost invisible and convenient for sports
c) the two types are hard and soft. soft lenses are more comfortable but carry a higher risk of infections
52
how is laser eye surgery done?
1) the laser can be used to vaporise tissue, changing the shape of the cornea, therefore changing how much light is refracted.
2) slimming it down makes it less powerful, so less light is refracted. changing the shape so that its more powerful will mean that more light is refracted
53
advantages and disadvantages of laser eye surgery?
ADVANTAGES: the surgeon can control how much tissue to take off and completely corrects vision. also it is permanent.
DISADVANTAGES: there are risks of complications such as an eye infection or the eye reacting in a way that makes your vision worse than before
54
a) what is replacement lens surgery?
b) what vision problem does it solve?
c? how is it done?
a) it is the replacement of the lens of the eye
b) treats hyperopia
c) the natural lens of the eye is removed and an artificial lens, made of clear plastic is inserted in its place
55
disadvantages of replacement eye surgery?
as it involves work inside the eye, replacing the lens carries higher risks than laser eye surgery. including possible damage to the retina (which could resort in loss of sight)
56
what is the core body temperature?
the temperature inside your body where your organs are
57
how does the body sense changes in temperature?
1) there is a thermoregulatory centre in the brain, which contains receptors that are sensitive to the temperature of the blood through the brain
2) the thermoregulatory centre also receives impulses from temperature receptors in the skin, giving information about the skin temperature
58
what are antagonistic receptors?
when effectors work at the same time to achieve a very precise condition (eg temperature) and this mechanism allows a more sensitive response
59
what does the body do when you're too hot?
1) hairs lay flat
2) sweat is produced by sweat glands and evaporates from the skin. this transfers energy into the environment
3) the blood vessels supplying the skin dilate more so blood flows close to the surface of the skin. this is called vasodilation and helps transfer energy from the skin into the environment
60
what does the body do when you're too cold?
1) hairs stand up and trap an insulating layer off hair
2) no sweat is produced
3) blood vessels supplying the skin capillaries constrict to close off the skins blood supply. this is called vasoconstriction
4) also the body shivers , this needs respiration which transfers some energy to warm the body
61
what are hormones?
chemical molecules released directly in the blood
62
how are hormones carried and where are they carried to?
they are carried in the blood and they are carried to other parts of the body, but only particular cells in particular organs (called target organs)
63
what do hormones control?
things in organs which need constant adjustment
64
where are hormones produced and secreted in?
various glands called endocrine glands which make up the endocrine system
65
what is the role of the pituitary gland?
1) produces many hormones that regulate the body's conditions
2) it is also called the master gland because these hormones act on other glands, directing them to release hormones to bring about change
66
what is the role of the thyroid gland?
produces thyroxine which is involved in regulating things like the rate of metabolism, heart rate and temperature
67
what is the role of the adrenal gland?
produces adrenaline, which is used to prepare the body for a 'fight or flight' response
68
what is the role of the ovaries?
produces oestrogen, which is involved in the menstrual cycle
69
what is the role of the pancreas?
produces insulin, which is used to regulate the blood glucose levels
70
what is the role of the testes?
produces testosterone, which controls puberty and sperm production in males
71
what are some key differences between nerves and hormones?
1) nerves have very fast action, whereas hormones have slower action.
2) nerves act for a very short time, whereas hormones act for a long time.
3) nerves act on a precise area, whereas hormones act in a more general area
72
how can you identify a nervous response?
if the information in your body is passed to the effectors really quickly as its no good using hormones to carry the message as they're too slow
73
how can you identify a hormonal response?
if the effects of it lasts a long time. for example, adrenaline happens really quickly however even afterwards, you still feel wobbly for a while
74
how can you differentiate between hormonal responses and nervous responses easily in an exam?
look at the speed in which it happens and also how long it lasts
75
what is blood glucose concentration controlled by?
the pancreas
76
what happens when blood glucose levels are too high?
the pancreas secretes the hormone, insulin, which causes glucose to move from the blood into the cells. in liver and muscle cells, the glucose is converted into glycogen for storage
77
what happens when blood glucose levels are too low?
the pancreas secrets the hormone, glucagon, which causes the stored glycogen in the liver cells to covert back to glucose and leave the cells
78
what is diabetes?
diabetes is a non-communicable disease which affects your ability to control your blood sugar levels, there are two types
79
what is type 1 diabetes?
it is when there pancreas produces little or no insulin.
this means that a person's blood glucose level can rise to a level that can kill them
80
what are the treatments for type 1 diabetes and how do they work?
-INSULIN THERAPY-
1) this usually involves several injections of insulin throughout the day, most likely at mealtimes. this makes sure that the glucose is removed from the blood quickly once the food has been digested, stopping the level getting too high. its very effective
2) limiting the intake of foods that are rich in simple carbohydrates (eg sugar), as it causes the blood glucose to rise rapidly.
3) also taking regular exercise to help remove excess glucose from the blood
81
for a patient with type 1 diabetes, what factors determine how much insulin is needed to be injected?
diet and how active they are, because a normal metabolism of cells removes glucose from the blood, so more vigorous exercises remove much more glucose from the blood
82
what is type 2 diabetes?
when a person becomes resistant to their own insulin, the cells dont respond properly to the hormone.
this could cause a person's blood glucose level to rise dangerously
83
what is a risk factor for type 2 diabetes?
obesity
84
how can type 2 diabetes be controlled?
eating a carbohydrate- controlled diet and getting regular exercise
85
what is the function of the kidneys?
1) the kidneys act as filters to 'clean the blood' . they make urine by taking waste products out of your blood.
2) substances are filtered out of the blood as it passes through the kidneys, this process is called filtration.
3) useful substances like glucose, and some ions and the right amount of water are then absorbed back into the blood. this process is called selective reabsorbtion
86
how is urea created?
1) proteins and amino acids cant be stored in the body, so any excess amino acids are converted into fats and carbohydrates, which can be stored. (THIS HAPPENS IN THE LIVER AND IS CALLED DEAMINATION)
2) ammonia is a waste product of this process
3) because ammonia is toxic, it is then converted to urea in the liver.
4) urea is then transported to the kidneys, where it is filtered out of the blood and excreted from the body in urine
87
how is the amount of ions in the body regulated?
1) ions such as sodium are taken into the body in food, then absorbed into the blood.
2) if the ion (or water) content of the body is wrong, this could upset the balance between ions and water, meaning that too much or too little water is drawn into the cells by osmosis. this could damage the cells, meaning they wont work normally.
3) ions are lost in sweat, as this is not regulated, the right balance of ions must be maintained by the kidneys. so the right amount of ions is reabsorbed into the blood after filtration and the rest is removed from the body in urine
88
how is the amount of water in the body regulated?
1) drinking water increases the volume water in our body.
2) so we lose some of that water from the skin in sweat, or the lungs by breathing it out.
3) however those are not regulates, therefore the amount of water is balanced by the volume we consume and the volume removed by the kidneys in urine
89
what is the concentration of urine controlled by and where is it secreted from?
1) a hormone called anti-diuretic hormone (ADH).
2) it is secreted from the pituitary gland
90
how are water levels controlled when there is TOO MUCH water in the blood?
1) a receptor in the brain detects that the water content is too high.
2) the coordination centre in the brain receives the information and coordinates a response.
3) the pituitary gland releases less ADH, so less water is reabsorbed from the kidney tubules
91
what would happen if the kidneys did not work properly?
waste substances build up in the blood and you lose your ability to control the levels of water an ions in your body, eventually, this results in death
92
how can people with kidney failure be kept alive?
1) a dialysis treatment. this is when a machine does the job of the kidneys.
2) kidney transplant
93
how does the dialysis machine work?
1) the person's blood flows between partially permeable membranes, surrounded by dialysis fluid. the membranes are permeable to things like ions and waste substances. but not big molecules like proteins (just like in the kidney)
2) the dialysis fluid has the same concentration of dissolved ions and glucose in healthy blood
3) this means that useful dissolved ions and glucose wont be lost from the blood during dialysis.
4) only waste products and excess ions and water will diffuse across the barrier
94
1) how often does dialysis have to take place?
2) how long is each session?
1) around 3 times a week. it has to be done regularly to keep the concentrations of dissolved substances in the blood at normal levels, and remove the waste substances
2) 3-4 hours
95
what are some downsides to dialysis?
1) could cause blood clots or infection
2) not a pleasant experience and is very costly for the NHS
96
what are some pros and cons to kidney transplants?
PROS-
1) cheaper than dialysis in the long run
2) cures the patient
CONS-
1) long waiting lists
2) the kidney could be rejected by the immune system
3) have to take drugs to prevent rejection
4) you can only really take organs from people who have agreed to be on the organ donor register or carry a donor card. plus their relatives must agree too so this means that there is a very low chance of getting a donor
97
what happens at puberty for men and women?
the body starts releasing sex hormones that trigger off secondary sexual characteristics
98
1) what is the main reproductive hormone for men?
2) where is it produced?
3) what is its main function?
1) testosterone
2) produced by the testes
3) it stimulates sperm production
99
1) what is the main reproductive hormone for women?
2) where is it produced?
3) what is its main function?
1) oestrogen
2) produced by the ovaries
3) is involved in the menstrual cycle and brings about physical changes
100
describe the 4 stages of the menstrual cycle
STAGE 1- from day one to four, the uterus lining breaks down down.
STAGE 2- from day four to fourteen, the uterus lining builds up again into a thick spongy layer full of blood vessels, ready to receive a fertilised egg.
STAGE 3- on day fourteen, one egg is developed and released from the ovaries (ovulation).
STAGE 4- from day fourteen to twenty eight, the uterus wall is maintained, if no fertilised egg has landed on it, the lining starts to break down and the whole cycle starts again
101
what hormones is the menstual cycle controlled by?
1) FSH (follicle-stimulation hormone)
2) oestrogen
3) LH (luteinising hormone)
4) progesterone
102
where is FSH produced and what is its function?
it is produced in the pituitary gland and it causes the egg to mature from the ovaries, in a structure called a 'follicle'. it also stimulated the ovaries to produce oestrogen
103
where is oestrogen produced and what is its function?
its produced in the ovaries and it causes the uterus lining to grow. it stimulates the release of LH (which releases the egg) and inhibits the release of FSH
104
where is LH produced and what is its function?
its produced by the pituitary gland and stimulated the release of an egg at day 14
105
where is progesterone produced and what is its function?
its produced in the ovaries by the remain of the follicle after ovulation and it maintains the lining of the uterus during the second half of the cycle, when the level of progesterone falls, the lining breaks down. it also inhibits the release of LH and FSH
106
how can oestrogen be used to reduce fertility?
1) oestrogen can be used to prevent the release of an egg, so it can be used as a method of contraception.
2) if oestrogen is taken everyday to keep the level permanently high, it inhibits the production of FSH, after a while, the egg development and production stop and stay stopped.
107
how can progesterone be used to reduce fertility?
it stimulates the production of thick mucus which prevents any sperm from getting through and reaching an egg
108
what is 'the pill'?
how effective is it?
disadvantages?
an oral contraceptive which contains oestrogen and progesterone. it is over 99% effective but can cause side effects like headaches and nausea, and doesnt protect against STDs
109
whats another pill alternative to 'the pill'?
a progesterone-only pill. it has fewer side effects than the pill and is just as effective
110
what are other hormonal contraceptives?
1) contraceptive patch.
2) the contraceptive implant.
3) contraceptive injection
4) intrauterine device (IUD)
111
how does the contraceptive patch work?
contains oestrogen and progesterone and is a small (5x5) patch thats stuck to the skin, each patch lasts one week
112
how does the contraceptive implant work?
it is inserted under the skin of the arm and releases a continuous amount of progesterone, which stops the ovaries from releasing eggs, makes it hard for the sperm to swim to the egg, and stops any fertilised egg implanting in the uterus. an implant can last for three years
113
how does the contraceptive injection work?
contains progesterone. each dose lasts two to three months
114
how does an IUD work?
its a T- shaped device which is inserted into the uterus to kil sperm and prevent implantation of a fertilised egg. there are two main types:
PLASTIC IUD- it releases progesterone.
COPPER IUD- prevents the sperm surviving in the uterus .
115
what are barrier methods of contraception?
non- hormonal methods of contraception which are designed to stop the egg and sperm from meeting
116
what are some barrier methods of contraception and how do they work?
1) CONDOMS, either worn by the male (over the penis) or female (in the vagina) and prevent against STDs.
2) DIAPHRAGM, a plastic cup that fits over the cervix to form a barrier and must be used wutg spermicide.
3) SPERMICIDE, can be used by itself but its ot as effective (70-80%) and its a substance that disables or kills the sperm
117
what is sterilisation?
cutting or tying the fallopian tubes in a woman or sperm duct in a male. this is permanent but there is a small chance that the tubes can rejoin
118
what is a natural method of contraception?
tracking the woman's menstrual cycle and avoiding sexual intercourse while the woman is the most fertile but its not very effective
119
what is abstinence?
refraining from having sex
120
what can be used to increase fertility?
the hormones FSH and LH can be given to the woman as a fertility drug to stimulate ovulation
121
why can some women not get pregnant?
they have low FSH levels and this means that eggs cant mature. therefore no eggs are released and they cant get pregnant
122
what is an advantage of using FSH and LH to improve fertility?
helps a lot of women get pregnant
123
what are some disadvantages to using FSH and LH to improve fertility?
1) it doesnt always work- some women have to do it multiple times and it can be expensive
2) too many eggs can be stimulated, resulting in unexpected pregnancies (twins, triplets ect)
124
how does an IVF work?
1) involves collecting eggs from the woman's ovaries and fertilising them in a lab using the man's sperm.
2) the IVF treatment can also involve a technique called ICSI, where the perm is directly injected into the egg. this is useful if the man has a very low sperm count.
3) the fertilised eggs are then grown in a laboratory incubator.
4) once the embryos are tiny balls of cells, one or two of them are transferred to the woman's uterus to improve the chance of pregnancy.
5) FSH and LH is given to the woman before egg collectionto stimulate several eggs to mature
125
the benefit of an IVF?
helps an infertile couple have a child
126
what are disadvantages to an IVF?
1) multiple births can happen if more than one embryo grows into a baby- these are risky for the bother and baby (theres a higher chance of a miscarriage/ stillbirth)
2) the success rate is low (only around 26% in the UK), this makes the process very stressful and upsetting if there are multiple failures.
3) there are physical drawbacks because of the strong reaction from the hormones. for example, vomiting, abdominal pain and dehydration)
127
different advances in technology which have helped improve IVF?
1) advances in microscope techniques
2) development specialised micro-tools
3) development of time lapse imaging
128
how has the development of specialised micro-tools helped improve IVF?
1) they can be used on eggs and sperm under the microscope
2) they're also used to remove single cells from the embryo for genetic testing (checking if its healthy)
129
what is the development of time- lapse imaging and how did it help improve IVF?
1) using a microscope and a camera built into the incubator
2) means that the growth of the embryos are continuously monitored to help identify those that are more likely to result in a successful pregnancy
130
why are some people against IVF (ethical) ?
1) the process of IVF often results in unused embryos that are eventually destroyed. these can be seen as unethical as the embryo is potential human life.
2) the genetic testing of the embryos before implantation also raises the ethical issues as some people think it could lead to preferred characteristics, such as gender or eye colour
131
when is adrenaline produced?
during stressful or scary situations- your brain detects fear or stress and sends nervous impulses to the adrenal glands, which respond by secreting adrenaline
132
what does adrenaline do to the body?
gets the body ready for 'fight or flight' by triggering mechanisms that increase the supple of oxygen and glucose to cells in the muscles. eg increasing heart rate
133
what is negative feedback?
controlling the hormone levels in the blood when the body detects that the level of a substance has gone above or below the normal level. this triggers a response
134
how is thyroxine controlled by negative feedback
1) thyroxine controls metabolic rate and the stimulation of protein synthesis for growth and development.
2) the negative feedback system keeps the amount of thyroxine in the blood at the right level.
2) when the level of thyroxine in the blood is higher than normal, secretion TSH is from the pituitary gland is inhibited and this reduces the amount of thyroxine released from the thyroid gland, so the level in the blood falls back towards normal
135
what is thyroxine made out of?
iodine and amino acids
136
what is the use of auxin?
it is a plant hormone that controls growth near the tips of the shoots and roots
137
what does auxin work in resonse to?
light (phototropism) and gravity (geotropism)
138
how does auxin work in the tips?
it is produced in the tips and moved backwards to stimulate the cell elongation process which occurs in the cells just behind the tips
139
what can happen if the tip of a shoot is removed?
no auxin is produced and available and the shoot may stop growing
140
what is the benefit and drawback of extra auxin?
promotes more growth in the shoot but inhibits growth in the root
141
in what direction does the shoot grow in (phototropism) ?
1) when the shoot tip is exposed to light, more auxin accumulates on the side thats in the shade than thats in the light.
2) this makes the cells elongate faster on the shaded side , so the shoot bends towards the light
142
in what direction does the shoot grow in (geotropism)
1) when a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side.
2) this causes the lower side to grow faster, bending the shoot upwards
143
in what direction does the root grow in (geotropism) ?
1) a root growing sideways will have more auxin on its lower side.
2) but in the root, the extra auxin inhibits growth. this means the cells on the top elongate faster, and the root bends downwards
144
what other uses does auxin have?
1) killing weeds
2) growing from cuttings with root powder
3) growing cells in a tissue culture
145
how can auxins be used for killing weeds?
as most weeds growing in fields of crops or in a lawn are broad leaved, selective weedkillers are specifically developed using auxins, which only affect broad-leaved plants.
- they totally disrupt their normal growth patterns which soon kills them, leaving the grass and crops untouched
146
how can auxins be used for growing a plant from cuttings with rooting powder?
normally if you stick cuttings into the soil, they wont grow. however, if you add rooting powder, which contains auxins, they'll produce roots rapidly and start growing as new plants.
this enables growers to produce a lot of clones of a really good plant very quickly
147
what are cuttings of a plant?
a part of a plant that has been cut off it, eg a branch with a few leaves on it
148
how can auxins to grow cells in tissue cultures?
auxins can be added to the growth medium (as long as nutrients) to stimulate the cells to divide to form roots and shoots
149
what is gibberellin and what does it stimulate?
another type pf plant growth hormone.
IT STIMULATES:
- seed germination
- stem growth
- flowering
150
how can gibberellin help to control dormancy?
lots of seeds wont germinate until they've been through certain conditions.
seeds can be treated with gibberellin to alter dormancy and make them germinate at times of year that they wouldnt.
this also helps to make sure all the seeds in a batch germinate at the same time
151
how can gibberellin help to induce flowers?
some plants require certain conditions to flower, for example, longer days or higher temperatures.
if these flowers are treated with gibberellin, they will flower without any change in their environment.
- gibberellin can also be used to grow bigger flowers
152
how can gibberellin be used to grow larger fruit?
seedless varieties of fruit often to not grow as large as seeded fruit.
however, if gibberellin is added to these fruit, they will grow larger to match the normal types
153
what is ethene and what does it stimulate?
ethene is a gas produced by ageing parts of a plant.
it influences the growth of the plant by controlling cell division.
it also stimulates enzymes whiich causes the fruit to ripen
154
when can ethene be used to ripen fruits?
when the fruits are on the plant or being transported to the market
155
how can ripening be delayed?
adding chemicals that block ethene's effect on the fruit or reduce the amount of ethene that the fruit can produce when the fruit is in storage.
furthermore, some chemicals can react with ethene to remove it from the air
156
how can ripening be delayed?
adding chemicals that block ethene's effect on the fruit or reduce the amount of ethene that the fruit can produce when the fruit is in storage.
furthermore, some chemicals can react with ethene to remove it from the `
