5. Homeostasis and Response Flashcards
1
Q
What are the two communication systems in the body?
A
The nervous system and the endocrine system
2
Q
How does the nervous system communicate with parts of the body?
A
Electrical impulses along neurones
3
Q
How does the endocrine system communicate with parts of the body?
A
Hormones (chemical messages) via the blood
4
Q
What are the two parts that make up the nervous system?
A
The central nervous system and the peripheral nervous system
5
Q
What is a stimulus?
A
A change in the environment which causes a response in the body
6
Q
How many organs can detect stimuli?
A
5
7
Q
What stimuli can ears detect?
A
Sound and balance
8
Q
What stimuli can eyes detect?
A
Light
9
Q
What stimuli can skin detect?
A
Temperature and pressure (pain)
10
Q
What stimuli can the nose detect?
A
Chemicals
11
Q
What stimuli can the tongue detect?
A
Chemicals
12
Q
Receptors for sound and balance?
A
Cochlea
13
Q
Receptors for light?
A
Rods and cones on retina
14
Q
Receptors for temperature and pressure?
A
Mainly nerve endings on the skin
15
Q
Receptors in the nose?
A
Olfactory receptors
16
Q
Receptors on the tongue?
A
Found on taste buds
17
Q
What is a sense organ?
A
Organ made up of a cluster of receptor cells, which are sensitive to specific stimuli
18
Q
Describe the pathway of an electrical impulse in the nervous system
A
Stimulus - receptor- sensory neurone - coordinator (CNS) - motor neurone - effector - response
19
Q
What are sensory neurones?
A
Cells that carry impulses from sense organs to CNS
20
Q
What are motor neurones?
A
Cells that carry impulses to make effector organs respond
21
Q
What is an effector?
A
A muscle or gland - muscles respond to arrival impulses by contracting
22
Q
How do muscles respond to arrival impulses?
A
By contracting
23
Q
What is the cerebral cortex concerned with?
A
Consciousness, intelligence, memory and language
24
Q
What is the cerebellum concerned with?
A
Mainly coordinating muscular activity and balance
25
What is the medulla concerned with?
Unconscious activities e.g. Controlling heartbeat, breathing
26
What is the hypothalamus concerned with?
Controlling body temperature
27
What is the pituitary gland concerned with?
Produces many different hormones which play a big part in coordinating and controlling body systems
28
How can matching changes in behaviour with the damaged part of the brain help scientists?
They can map the function of some parts of the brain
29
How can electrical stimulation of the brain help scientists?
They cans stimulate parts of the brain and see what effects it has e.g. hunger, fear
30
How can MRI scans of brains help scientists?
So they can understand development. Can link a loss of a certain function with damage to a particular region of the brain
31
How do scientists map brain regions?
By studying patients with brain damage, electrically stimulating areas of the brain and using MRI scans
32
What are potential problems when treating brain complications?
Processes involve neurones and chemicals released in synapses which can easily be damaged
Drugs do not always reach brain
Surgery is difficult as its not fully understood what part of brain does what
33
What are reflexes for?
To protect the body from harm or control basic body functions
34
What extra neurone is used in reflex actions?
Relay neurone
35
How does caffeine affect reaction time?
It decreases reaction time
36
What happens when an electrical impulse arrives at the synaptic knob?
Vesicles containing neurotransmitters migrate to the nerve cell membrane
37
Where do vesicles release neurotransmitters?
Into the synaptic gap where they diffuse across to the next neurone and attach to their receptor sites
38
Where may synapses occur?
Between sensory and relay neurones, and between relay and motor neurones
39
What are neurotransmitters?
Chemicals that diffuse between neurones and attach to receptor sites
40
What is the eye?
A sense organ containing many receptors that are sensitive to light intensity and colour
41
How are light sensitive cells arranged in the eye?
They are arranged together inside the back of the eye in a light-sensitive layer known as the retina
42
What is a blind spot?
The point where the optic nerve leaves the eye
43
What is the function of the cornea?
Changes direction of light rays entering the eye
44
Is the cornea transparent?
Yes
45
What is the function of the iris?
It is a muscle that controls the size of the pupil
46
What is the function of the lens?
A clear disk that fine-tunes, focuses light by changing shape
47
What is the function of the retina?
Converts light to electrical impulses
48
What is the function of the optic nerve?
Where impulses are sent from the brain to the retina
49
Why does the pupil constrict in bright light?
To reduce the amount of light entering the eye which could damage the retina
50
What is binocular vision?
Vision using two eyes, the range of vision overlaps
51
What is monocular vision?
Vision using one eye, the range of vision does not overlap
52
What is an advantage of binocular vision?
Judged distance and ability to see in 3D
53
What is a disadvantage of binocular vision?
Smaller field of view
54
What is an advantage of monocular vision?
Eyes on side of head so wider field of vision
55
What is a disadvantage of monocular vision?
Unable to judge distance, no 3D
56
What do the ciliary muscles and suspensory ligaments do?
Act together in the eye to pull or push on the lens
57
What happens when the lens in the eye is flatter?
Light is refracted more
58
What is myopia?
Short-sightedness
59
What is hyperopia?
Long-sightedness
60
What is short sightedness?
The inability to focus on distant objects
61
What is long sightedness?
The inability to focus on near objects
62
How can short sightedness be corrected?
Concave lens to refract light outwards before hitting the cornea so image focuses on retina
63
How can long sightedness be corrected?
Convex lens to refract light inwards so it lands on the retina
64
What does laser eye surgery do?
Changes the shape of the cornea, not the lens
65
What are replacement lenses?
Adding another lens inside the eye, permanent contact lenses, or removing faulty lenses and putting a new one on
66
Advantages of contact lenses?
Can't be seen, good for sports
67
Disadvantages of contact lenses?
Can cause eye infections, expensive, need to be sterilised each night
68
Advantages of laser eye surgery?
The majority of people don't need to wear glasses, can be used for long and short sightedness
69
Disadvantages of laser eye surgery?
Only available to adults when eyes stop growing
70
Advantages of replacement lenses?
Permanent corrections to visual impairment
71
Disadvantages of replacement lenses?
Damage to retina, cataracts, infection
72
How does the eye accommodate for a distant object?
Relaxed muscle, taut ligaments - longer, flatter, narrower lens
73
How does the eye accommodate for a near object?
Contracted muscle, slack ligaments - shorter, fatter lens
74
What is homeostasis?
The control of constant internal conditions
75
What parts of the body does homeostasis involve?
The nervous system, the endocrine system and many body organs
76
How are hormones transported to their target organ?
By the bloodstream
77
What to the nervous and endocrine systems work together to do?
Coordinate responses to changes in the external and internal environment
78
What does homeostasis involve the control of?
* water and ions
* temperature
* blood glucose levels
79
What hormones are produced at the pituitary gland?
* antidiuretic hormone, ADH
* thyroid stimulating hormone, TSH
* follicle stimulating hormone, FSH
* luteinising hormone, LH
* growth hormones
80
What is the pituitary gland also known as?
The master gland
81
Where is the pituitary gland?
The brain
82
What hormone is produced at the thyroid gland?
Thyroxin
83
What is thyroxin?
A hormone that helps regulate heart rate, metabolism and temperature
84
Where is the thyroid gland located?
The front of the neck
85
What hormone do the adrenal glands produce?
Adrenaline
86
What is adrenaline?
A hormone which is used to prepare the body for a 'fight or flight' response
87
Where are the adrenal glands located?
The kidneys
88
What hormones does the pancreas produce?
Glucagon and insulin
89
What do insulin and glucagon do?
Regulate blood glucose levels
90
Where are insulin and glucagon produced?
Pancreas
91
What hormone do the ovaries produce?
Progesterone and oestrogen
92
What hormone do the testes produce?
Testosterone
93
What does testosterone do?
Controls puberty and sperm production
94
Why is it important to control water levels in the body?
Too much water moving in and out cells means they could be destroyed
95
Why is important to control body temperature?
Reactions in cells stop and you will die
96
Why is it important to control glucose levels in the blood?
Short term: die of a diabetic coma
Long term: organ damage especially eyes, also limbs - blood vessel damage
97
What is the body's core temperature?
37*C
98
What is the core temperature?
The temperature deep in the body e.g. in organs
99
What happens if core body temperature is too high?
Enzymes start to denature
100
What happens if core body temperature is too low?
Few enzyme/substrate collision and so chemical reactions slow down
101
What can affect body temperature?
* external temperature rising or falling
* fevers caused by disease
* energy produced in muscles from respiration during exercise
102
Why does exercise affect body temperature?
Heat is a by-product of respiration
103
What are arterioles?
Smaller arteries
104
What do the thermoreceptors in the hypothalamus do?
Detect blood temperature
105
What do the thermoreceptors in the skin do?
Detect external temperature
106
What do the receptors in the hypothalamus do?
* sensitive to temperature changes
| * monitor temperature of the blood flowing through brain
107
What do the thermoreceptors in skin do?
* provide extra information - impulses sent to thermoregulatory centre giving information about skin temperature
* can detect a difference of 0.5*C
108
How does vasodilation work?
When the body is too hot:
* blood flows to surface capillaries
* pre-capillary sphincter muscle dilates
* much heat radiates from skin surface
109
How does vasoconstriction work?
When the body is too cold:
* little blood flows through surface capillaries
* pre-capillary sphincter muscle constricted
* little heat radiates from skin surface
110
When does sweat cool the body?
When the sweat evaporates
111
How is body temperature maintained?
Negative feedback
112
What is the body's response if temperature is too high?
* blood vessels supplying the skin capillaries dilate so more blood flows through capillaries and more heat is lost - vasodilation
* sweat glands release more sweat which cools the body as it evaporates
* pilorelaxation
113
What is the body's response if temperature is too low?
* blood vessels supplying the skin capillaries constrict to reduce the flow of blood through the surface capillaries - vasoconstriction
* muscles may shiver - their contraction needs respiration which release some energy as well as heat
* piloerection - hairs stand up, trapping a layer of insulated air
114
What is responsible for the level of glucose in the blood?
Sugar and other carbohydrates in food
115
How are blood glucose levels kept relatively constant?
Insulin and glucagon
116
Where are insulin and glucagon made?
The pancreas
117
What do insulin and glucagon ensure?
That cells have a constant supply of energy
118
What happens when blood glucose levels rises above ideal range?
* insulin is released causing liver to remove any glucose which is not needed from the blood
* soluble glucose is converted to the insoluble carbohydrate, glycogen
119
Where is glycogen stored?
In the liver
120
What does insulin do?
Causes the liver to remove excess glucose
121
What does insulin convert glucose into?
Glycogen
122
What happens when blood glucose levels falls below ideal range?
* the pancreas secretes glucagon causing the liver to break down glycogen
* glycogen is converted back to glucose
123
What does glucagon do?
Makes the liver break down glycogen, converting it back to glucose
124
Properties of type 1 diabetes?
* early onset
* caused by a sudden inability to produce insulin
* fast diagnosis
125
What are type 1 diabetes caused by?
A sudden and almost complete inability to produce insulin
126
Symptoms of type 1 diabetes?
* thirst
* weight loss
* tiredness
127
Treatment for type 1 diabetes?
Insulin injections
128
Properties of type 2 diabetes?
* either when body is unable to make enough insulin or a fault in the body's response to insulin
* caused by being overweight
* more gradually onset of symptoms
129
What are type 2 diabetes caused by?
* when the body is unable to make enough insulin
* or when there's a fault in the body's response to insulin (hormone cannot move glucose into cells)
*ultimately caused by being overweight
130
Symptoms of type 2 diabetes?
* tiredness
* thirst
* need to pass urine more often
* in some: blurred vision
* in some: weight loss
131
Treatment for type 2 diabetes?
A balanced diet and exercise - to control blood sugar levels as they are given tablets which stimulate insulin production or help the body use insulin
132
How is water lost from the body?
* urine
* sweat
* breath
* (faeces)
133
What is lost from the body as well as water?
* salt (ions)
| * urea
134
What percentage of water is lost through urine on a cold day?
62%
135
What percentage of water is lost through breath on a cold day?
20%
136
What percentage of water is lost through faeces on a cold day?
5%
137
What percentage of water is lost through sweat on a cold day?
13%
138
Why is more water lost to sweat on a warm day?
The body is trying to cool down, so it sweats more. The sweat evaporates and this sweat contains water
139
Why is it important to remove waste products from the body?
* CO2 forms an acidic solution in the blood and can be toxic
| * urea is toxic
140
Where is urea produced?
In the liver
141
How is urea produced?
By the deamination (breakdown) of excess amino acids
142
How is urea removed from the body?
By the kidneys in the urine, which is temporarily stored in the bladder
143
What do the kidneys control?
The balance of water and ions
144
What will happen if the water or ion content of the body is wrong?
Too much water may move in or out of cells and damage them
145
How do the kidneys produce urine?
* filtration of the blood: small molecules pass out of the blood into the tubule
* selective reabsorption of useful substances (e.g. glucose, some ions and water)
146
What moves into the kidney tubules?
Glucose, amino acids, mineral salts and urea move out of the blood into the kidney tubules
147
How do substances move into the kidney tubules?
By diffusion down a concentration gradient
148
What does not diffuse into the kidney tubules?
Blood cells. They are too big to pass through the membrane of the tubule
149
How much glucose is reabsorbed back into the blood from the kidney tubules?
All of it
150
How is glucose reabsorbed into the blood from the kidney tubules?
By active transport
151
How much water and dissolved mineral ions are reabsorbed from the kidney tubules?
It varies depending on what it needed by the body - selective reabsorption
152
What happens to urea after it has diffused to the kidney tubules?
Urea is lost in the urine
153
When do the kidneys produce urine?
All the time
154
Do the kidneys have a rich blood supply?
Yes
155
What is filtered from the Bowman's Capsule into the tubule?
* glucose
* amino acids
* mineral salts
* urea
156
What is reabsorbed by the blood in the kidneys?
* all glucose (by active transport)
| * varied amounts of water and mineral ions (selective reabsorption)
157
Adaptations of the kidney tubules for reabsorption?
* tubule wall is one cell thick
* cells lining the wall contain large numbers of mitochondria (especially for active transport)
* the cells lining the wall contain microvilli
158
What does a presence of glucose in urine mean?
High blood glucose levels; it has not been reabsorbed into the blood
159
What does a presence of protein (trace) in urine mean?
Damage to capsule nephron allowing proteins through
160
What is ADH?
Anti-diuretic hormone
161
What is diuresis?
Increased urine production
162
What hormone controls the water level in the body?
ADH
163
What does ADH act upon?
The kidney tubule
164
What is ADH released by?
The pituitary gland
165
When is ADH released?
When the blood is too concentrated
166
What does ADH do?
Causes more water to be reabsorbed back into the blood from the kidney tubules
167
What happens when water concentration is high?
* less ADH is secreted by the pituitary gland
* the kidneys reabsorb less water
* lots of dilute urine is produced
168
What happens when water concentration is low?
* more ADH is secreted by the pituitary gland
* the kidneys reabsorb more water
* little concentrated urine is produced
169
What are water levels controlled by?
Negative feedback
170
Examples of treatments for kidney failure?
* dialysis
| * transplant
171
How does dialysis work?
* dialysis fluid contains the same concentration of useful substances as the patients blood
* dialysis machine - persons blood leaves their body and flows between partially permeable membranes
* urea diffuses out into dialysis fluid from blood
* cells and large proteins cannot pass through dialysis membrane
172
What should successful dialysis do?
Restore concentration of substances back to normal, but needs repeating at regular intervals
173
What does dialysis fluid contain?
The same concentration of useful substances as the patient's blood does (glucose, mineral ions)
174
What to people who receive dialysis have to do?
Manage their diets carefully as this helps keep their blood chemistry as stable as possible
175
How do kidney transplants work?
Diseased or damaged kidneys are replaced with a healthy kidney from a donor
176
Problems with kidney transplants?
The donor kidney may be rejected by the recipient's immune system
177
How is kidney rejection prevented?
* tissue types of the donor and the recipient are matched as closely as possible
* immunosuppressant drugs are used
178
What hormones are in the female reproduction system?
* oestrogen
* progesterone
* LH
* FSH
179
What hormones are in the male reproduction system?
testosterone
180
What glands produce the female reproductive hormones?
ovaries and pituitary gland
181
What glands produce the male reproductive hormones?
testes
182
What are the secondary sexual characteristics females develop during puberty?
* growth spurt
* breasts develop
* external genitals grow and skin darkens
* pubic and armpit hair grow
* fat on hips, buttocks and thighs
* mature egg each month
* uterus grows and activates
183
What are the secondary sexual characteristics males develop during puberty?
* growth spurt
* pubic, armpit and facial hair
* larynx grows and voice breaks
* testes grow and become active
* produce sperm
* shoulders and chest broaden
* brain develops
184
What are female reproductive hormones involved in?
Control of menstrual cycle
185
What are male reproductive hormones involved in?
Sperm production
186
What does FSH stand for?
Follicle stimulating hormone
187
What does FSH do?
* stimulates a follicle to mature
| * stimulates ovaries to release oestrogen
188
What does LH stand for?
Luteinising hormone
189
What does LH do?
Stimulates ovulation
190
What is ovulation?
The release of an egg
191
Explain the menstrual cycle.
* FSH is secreted by the pituitary gland and causes eggs to mature in the ovaries and also stimulates the ovaries to produce oestrogen
* Oestrogen inhibits further production of FSH
* Oestrogen stimulates womb lining to build up
* Oestrogen stimulates the pituitary gland to produce LH
* LH stimulates ovulation from ovary in the middle of the menstrual cycle
192
What is the role of progesterone in the menstrual cycle?
* maintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy
* progesterone inhibits FSH and LH
193
What hormone causes eggs to mature?
FSH
194
What is the role of oestrogen in the menstrual cycle?
* inhibits FSH production
* stimulates womb living to build up
* stimulates pituitary gland to produce LH
195
What are contraceptives used for?
To prevent pregnancy
196
What are oral contraceptives?
Pills which may contain oestrogen only, progesterone only, or a mixture of the two
197
What are some features of the oestrogen only pill?
* taken every day
* keeps oestrogen levels permanently high
* inhibits FSH production
* egg maturation and release will stop
198
Why was a combined oestrogen and progesterone pill developed?
Following concerns regarding links with oestrogen and side effects e.g. blood clots
199
How does a progesterone pill reduce fertility?
It stimulates production of a thick, cervical mucus which prevents sperm reaching an egg.
It can inhibit egg maturation and therefore release
200
What has more side effects, the combined pill or progesterone only?
Combined pill
201
Benefits of combined oral contraception?
* over 99% effective of reducing pregnancy
| * shown to reduce risks of getting some types of cancer
202
Problems of combined oral contraception?
* not 100% effective so there is a very slight chance of getting pregnant
* side effects include headaches, nausea, irregular menstrual bleeding and fluid retention
* doesn't not protect against STDs
203
Side effects of combined oral contraception?
* headaches
* nausea
* irregular menstrual bleeding
* fluid retention
204
What types of contraception are there?
* oral
* skin patches, implants and injections
* intrauterine devices
* surgical methods
* natural methods
* barrier methods
205
What are the types of skin contraception available?
* contraceptive patches
* contraceptive implants
* contraceptive injections
206
What hormones do contraceptive patches contain?
Oestrogen and progesterone
207
How big are contraceptive patches?
5x5cm
208
How long do contraceptive patches last?
One week approx.
209
What are the types of barrier contraception available?
* condoms
| * diaphragms
210
What is the only form of contraception that can protect from STDs?
Condoms
211
What is a diaphragm?
A plastic cup that fits over the cervix. Has to be used with spermicide.
212
What are the types of natural contraception available?
abstinence - don't have sex just to be sure
213
What is not an effective contraceptive method?
Finding out when the menstrual cycle is most fertile and avoiding intercourse on those days
214
What are the types of surgical contraception available?
Sterilisation
215
What is sterilisation?
Cutting or tying the Fallopian tubes or sperm duct. It is permanent however there's a small chance the tubes could rejoin
216
What are intrauterine devices?
T-shaped devices inserted into the uterus to kill sperm and prevent implantation of a fertilised egg
217
What do plastic IUDs do?
Release progesterone
218
What do copper IUDs do?
Prevent sperm surviving in the uterus
219
What are the most effective types of contraception?
Hormone based - pills, injections, patches, vaginal rings and IUDs
220
What are the least effective forms of contraception?
Withdrawal
221
What does IVF stand for?
In vitro fertilisation
222
What is IVF?
A process that can be used to help couples who are experiencing difficulty having children
223
Explain the IVF process.
* FSH and LH are given to the woman to stimulate the maturation of multiple eggs
* Eggs are then collected from the woman's ovaries
* Eggs are fertilised in a lab using the man's sperm
* Fertilised eggs grow into embryos in a laboratory incubator
* Once embryos have formed a couple are transferred to the woman's uterus
224
Advantages of IVF?
• can give an infertile couple a child
225
Disadvantages of IVF?
* can lead to multiple births - higher risk of miscarriages and stillborns
* expensive procedure
* average success rates in the U.K. is 26%
* emotionally upsetting and stressful
* physically stressful as woman is treated with hormones - side effects include abdominal pain, vomiting and dehydration
226
Social issues with IVF?
* lots of children who could be adopted as an alternative
| * embryos are a potential human life and some are destroyed in the process
227
Ethical issues with IVF?
Some people think genetic testing of embryos could lead to the selection of preferred characteristics e.g. gender
228
Arguments for having IVF on the NHS?
* every couple should have the chance to have a child - infertility isn't a choice
* important for poorer couples - shouldn't be a privilege for the rich
229
Arguments against having IVF on the NHS?
* high cost of treatment - how many trials should people be allowed?
* used to help older woman with infertility - how old is acceptable?
* lots of children on adoption list
* more multiple births - high medical costs
* low success rates
* less money available for other treatments
230
How is does adrenaline prepare the body for 'flight or fight'?
* brain detects fear/stress
* brain sends impulses to the adrenal gland
* secrete adrenaline in response
* adrenaline increased oxygen and glucose supply to cells in brain and muscles e.g. increases heart rate
231
What is the body's response to adrenaline?
Increased supply of oxygen and glucose to cells in the brain and muscles - increased heart rate
232
What is TSH?
Thyroid stimulating hormone
233
What is thyroxine released in response to?
It is released in response to TSH from the pituitary gland
234
How does the body respond to thyroxine from the thyroid gland?
* stimulates the basal metabolic rate
| * plays an important role in growth and development e.g. It stimulates protein synthesis
235
An example of negative feedback?
Thyroxine release
236
What is negative feedback?
When the levels of certain substances in the body go above or below a normal level, the body triggers responses that bring these levels to normal range
237
What happens when the levels of certain substances rise above ideal level?
* level rises
* receptors detect change
* response lowers levels
238
What happens when the levels of certain substances fall below ideal level?
* level falls
* receptors detect change
* response raises levels
239
What are tropisms?
A growth movement in part of a plant in response to a directional stimulus
240
What is it called when plants grow towards a stimulus?
Positive response
241
What is it called when plants grow away from a stimulus?
Negative response
242
Why do plants need to be able to detect and respond to stimuli?
In order to survive e.g. plants sense light and grow towards it to maximise the amount they receive
243
Examples of plants responding to stimuli?
* sensing light and growing towards it to maximise the amount of light they receive
* respond to gravity to ensure their roots and shoots grow in the right direction
244
What type of plant growth responses are there to stimuli?
* phototropism (light)
* geotropism (gravity)
* hydrotropism (water)
245
What responses to light, water and gravity do shoots show?
* positive phototropism - maximise light
* negative hydrotropism
* negative geotropism - allows them to grow in the right direction in the absence of light
246
What responses to light, water and gravity do roots show?
* positive geotropism - anchorage
* positive hydrotropism - seek water
* negative phototropism
247
Why do shoots show positive phototropism?
To maximise the amount of light they receive
248
Why do shoots show negative geotropism?
It allows them to grow in the right direction in the absence of light
249
Why do roots show positive hydrotropism?
They seek water
250
Why do roots show positive geotropism?
For anchorage
251
What is auxin?
A plant hormone that controls growth near the tips of shoots and roots
252
What does auxin control?
It controls the growth of a plant in response to different stimuli
253
Where is auxin produced?
In the tips of shoots and roots and diffuses backwards
254
What does auxin stimulate?
Cell elongation which happens in the cells just behind the tips
255
What happens if the tip of a shoot is removed?
No auxin will be available and the shoot may stop growing
256
What happens in the shoots where auxin accumulates?
It stimulates shoot growth by elongation
257
What happens in the roots where auxin accumulates?
It inhibits root growth
258
Is there a nervous system in plants?
No
259
What does unequal distributions of auxin cause?
Unequal growth rates in plant shoots and roots
260
How does auxin help roots grow towards gravity?
* even distribution of auxin in root tip
* auxin diffuses downwards in the direction of gravity
* auxin accumulates behind tip of root
* auxin inhibits cell growth (on inside of root)
* root grows towards gravity
261
How does auxin help shoots grow away from gravity?
* even distribution of auxin in shoot tip
* auxin stimulates growth in shoots
* cells elongate on the lower side
* shoot grows away from direction of gravity
262
How does auxin help shoots grow towards light?
light from above: auxin diffuses to behind tip of shoot evenly
light from one side: auxin accumulates on shaded side of shoot - greater cell elongation on this side
263
Which plant hormones are used in agriculture?
* auxin
* gibberellins
* ethane
264
How is auxin used in agriculture?
* rooting powder
* weed killers
* cell tissue culture growth
265
How is auxin used in rooting power?
By dipping ends of cuttings in rooting powder chances of success are increased
266
Why is auxin used in rooting powder?
As the hormone stimulates growth of new roots
267
How is auxin used in weed killers?
* auxin naturally stimulates growth of new plants
| * auxin solution absorbed by leaves and send plants into rapid, uncontrolled growth - killing them
268
How is auxin used in cell tissue culture growth?
* auxin stimulates growth and cell division in the tissue culture
* helps to produce identical plants
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How are gibberellins used in agriculture and other industry?
* brewing industry
* promote flowing throughout the year
* increase size of fruit
270
Why are gibberellins used in the brewing industry?
* to end seed dormancy
| * speed up germination of barley seeds which are used to make malt
271
How is ethene used in agriculture?
To control the ripening of fruit
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How does ethene control the ripening of fruit?
* growers harvest fruit before they're ripe - less likely to be damaged
* fruit stored until needed
* warm temperatures and ethene mean stored fruit can be rapidly ripened when needed
273
What type of plants absorb more weed killer?
Broad leaved weeds will absorb more that grass plants
