Science - Biology - Homeostasis - B5 Flashcards
1
Q
why is it important that conditions inside your body are steady ?
A
cells need the right conditions to function properly
2
Q
what does homeostasis do ?
A
make sure the conditions in your body are right so it can function properly
3
Q
what is the definition of homeostasis ?
A
regulation of conditions inside your body to maintain a stable environment in response to changes in both internal and external conditions
4
Q
what are control systems ?
A
in your body to regulate your internal environment
5
Q
give 2 examples of control systems
A
nervous and hormonal systems
6
Q
give examples of conditions in your internal environment
A
- body temperature
- blood glucose content
- water content of the body
7
Q
what is a stimulus ?
A
a change to the environment you need to respond to
8
Q
what is the automatic control system made up of ?
A
receptors - coordination centre - effectors
9
Q
give examples of a coordination centre in your body
A
brain and spinal cord
10
Q
give examples of effectors
A
muscles / glands
11
Q
what are receptors ?
A
detect a stimulus when the level of something is too high or low
12
Q
what does the bodies automatic control system do ?
A
work together to maintain a steady system
13
Q
what does the coordination centre do ?
A
processes information and organises responses
14
Q
what do effectors do ?
A
respond to counteract the change bringing level back to optimum
15
Q
what is negative feedback ?
A
the mechanism that restores optimum level
16
Q
give an example of a negative feedback mechanism
A
optimum level -
level changes from optimum -
receptors detect change -
coordination centre recieves then processes information and organises a response -
effectors respond-
17
Q
what does automatic mean ?
A
brain doesn’t get involved
18
Q
what is the optimum body temperature ?
A
37 degrees
19
Q
why is it more difficult for a multicellular organism to respond to a stimulus ?
A
the cells need to communicate with each other first
20
Q
what systems do multicellular organism have to help them to react to a stimulus ?
A
hormonal and nervous systems
21
Q
what is the nervous system ?
A
a system which allows you to react to your surroundings and coordinate your behavior
22
Q
what is the nervous system made up of ?
A
neurones
23
Q
what are neurones ?
A
nerve cells
24
Q
what are receptors ?
A
cells which detect stimuli
25
give examples of receptors in the body
- taste receptors on tongue
-sound receptors in ears
- smell receptors in nose
- light receptors in the eyes
26
where are light receptor cells in the eye ?
they are covered on the retina
27
what is the central nervous system ?
where all the information from the receptors is sent and where reflexes are coordinated
28
where is the central nervous system in vertebrates ?
spinal cord and brain
29
What neurones is the CNS connected to ?
the sensory and motor neurones
30
what to neurones do for the CNS ?
transmit information and electrical impulses to and from the CNS
31
what are effectors ?
muscles or glands which respond to nervous impulses and bring a response to the stimulus
32
give examples on how effectors respond to the stimulus
muscles contract
glands secrete chemical substances called hormones
33
what are the different types of neurone ?
sensory neurones
relay neurones
motor neurones
34
what do sensory neurones do ?
carry information as electrical impulses from the receptors in the sense organs to the CNS
35
what do relay neurones do ?
carry electrical impulses from sensory neurones to motor neurones
36
where are relay neurones found ?
CNS
37
what are motor neurones ?
neurones that carry electrical impulses from the CNS to the effectors
38
show the transmission of information to and from the CNS
stimulus
receptors - sensory neurone
relay neurone - CNS
- motor neurone - effector
response
39
what is a synapse ?
the connection between 2 neurones
40
how do synapses work ?
the nerve signal is transferred by chemicals which diffuse across the gap, these chemicals set off a new electrical signal in the next neurone
41
describe step by step, a synapse
1. nerve impulses reach the end of the first neurone
2. chemicals are released
3. new impulse is set off in the next neurone
42
why do neurones transmit information quickly ?
they are transmitted by electrical impulses
43
how do synapses slow down nerve impulse transmissions ?
the diffusion of chemicals across the gap takes time
44
what are reflexes ?
fast automatic responses to a certain stimuli
45
how do reflexes work ?
they bypass your conscious brain completely when a quick response is essential
46
what do reflexes help with ?
they reduce your chances of being injured
47
give an example of how reflexes work
- if someone shines a bright light in your eyes your pupils automatically get smaller, so less light gets in your eyes = less damage
- adrenaline is a hormone which gets your body ready for action, so if you get a shock your body automatically releases adrenaline
- knee jerk reflex, doctors test this by tapping below the knee with a small hammer which stimulates pressure receptors making a muscle in the upper leg contract, this helps maintain posture and balance
48
what is a reflex arc ?
the passage of information in a reflex
49
where do the neurones in a reflex arc travel through ?
the spinal cord or unconscious part of the brain
50
describe step by step what happens in a reflex arc
1. when a stimulus is detected, impulses are sent along the sensory neurone to the CNS
2. when the impulses reach a synapse between the sensory and relay neurone they trigger chemicals to be released, these chemicals cause impulses to be sent along the relay neurone
3. when impulses reach the synapse between relay neurones and motor neurones the same thing happens
4. impulses travel along motor neurone to the effector
5. if effector is a muscle, it will respond by contracting, if its a gland, it will release hormones
51
give a summary diagram of a reflex arc
stimulus
receptor
snesory neurone - relay neurone - motor neurone
effector
response
52
give an example of a reflex arc if a bee stung you
1. cheeky bee stings finger
2. stimulation of pain from receptor
3. impulses travel along sensory neurone
4. impulses are passed along relay neurone via synapse
5. impulses travel along motor neurone via synapse
6. when impulses reach the muscles, it contracts
7. hand moves away source of pain #ouch
53
what is reaction time ?
the time taken to respond to a stimulus
54
what is reaction time affected by ?
- age
- gender
- drugs
55
describe the practical showing how caffeine affects reaction time
1. person being tested sits with their arm resting against a table
2. hold a ruler vertically between thumb and forefinger. Make sure the 0 end of the ruler is level with their thumb and finger
3. let go of ruler randomly
4. person being tested tries to catch ruler as fast as possible
5. reaction time is measured at the top of the ruler where it was caught at the top of the ruler
6. repeat several times and calculate a mean
person being tested should have drank a caffeinated after 10 minutes repeat these steps
56
what are the control variables of the reaction time experiment ?
- use the same person to catch the ruler each time
- person should use the same hand to catch the ruler
- ruler should be dropped from the same height
- make sure the person catching hasn't had caffeine before the start of the experiment
57
what are the safety issues of the reaction time experiment ?
- drinks need to be consumed outside of the science lab away from chemicals
- too much caffeine can cause side effect
58
how can you measure reaction time using technology ?
using a computer, the person tested has to click the mouse as soon as they see a stimulus on the screen such as a change in colour
59
how can computers be more accurate to measure reaction time ?
they remove human error as they can record reaction time in milliseconds
removes possibility that the person can predict when to respond as in the ruler test the catcher may anticipate when to catch by reading body language
60
what does the brain do ?
controls and coordinates everything you do , like running, breathing, jumping
61
what is the brain made up of ?
billions of interconnected neurones
62
what are the different regions of the brain ?
cerebral cortex
medulla
cerebellum
63
what is the cerebral cortex ?
the outer, wrinkly layer of the brain, responsible for things like consciousness, intelligence, memory language
64
what is the medulla ?
at the base of the brain, at the top of the spinal cord, controls unconscious activities like breathing and your heartbeat
65
what is the cerebellum ?
at the back of the brain, responsible for muscle coordination
66
what are scientists that research the brain called ?
neuroscientists
67
how do doctors study patients with brain damage ?
if a small part of the brain has been damaged, the effect this has on the patient tells us a lot about what the damaged part of the brain does, e.g if the patient went blind, you know the area damaged had something to do with vision
68
how is the brain electrically stimulated ?
by pushing a small electrode into the tissue and giving it a small zap of electricity
69
how can electrically stimulating the brain help us ?
it shows what parts of the brain does, e.g if the motor area is stimulated it causes muscles contraction
70
what is an MRI scan ?
a magnetic resonance imaging scanner
71
what does an MRI scan do ?
produces a very detailed picture of the brains structures
72
how does a MRI scan help ?
finds out what parts of the brain are active when people are trying to do things like listen to music / recall memory
73
how does electrical stimulation help the brain ?
can help reduce muscles tremors caused by disorders such as parkinsons disease
74
how is brain surgery helpful ?
can remove parts of the brain which cause seizures, treats epilepsy
75
what is the disadvantage of messing with the brain ?
its difficult
could causes increased problems with brain function
could cause physical damage
could cause brain damage/disease
76
what are the different structures of the eye ?
sclera
iris
retina
pupil
lens
cornea
optic nerve
ciliary muscles and suspensory ligaments
77
what does the sclera do ?
tough,supporting wall of the eye
78
what does the cornea do ?
transparent outer layer found at the front of the eye
79
pupil
hole at the centre of the eye through which light enters
80
iris
contains muscles which control the diameter of the pupil and therefore how much light enters
81
retina
layer at the back of the eye which contains 2 types of light repector cells
82
what are the 2 type of light receptor cells in the retina ?
- 1 is sensitive to light intensity
- 1 is sensitive to colour
83
lens
focuses light onto retina
84
ciliary muscles and suspensory ligaments
controls shape of the lens
85
optic nerve
carries impulses from receptors on the retina to the brain
86
what is the iris reflex ?
the reflex which helps protect the retina
87
what happens with the iris reflex if too bright light is shined in the eye ?
reflex is triggered to make pupil smaller, circular muscles in the iris contract and radial muscles relax to reduce amount of light which enters the eye
88
what happens to the iris reflex if light is too dim?
radial muscles contract and circular muscles relax which makes the pupil wider, allowing more light in
89
what is accommodation ?
the ability to look at near and distant objects through the unconscious part of the brain, the eye focuses light onto the retina by changing the shape of the lens
90
what happens in the eye if you want to look at near objects ?
1. ciliary muscles contract, which slackens suspensory ligaments
2. lens becomes more curved
3. increases amount by which it refracts light
91
what happens to the eye if you want to look at distant objects ?
1. ciliary muscles relax, which pulls the suspensory ligaments tightly
2. this makes the lens go less curved
3. it refracts light by a smaller amount
92
what happens if the lens in the eye cannot refract light by the right amount
the person is long or short sighted
93
what is long sightedness called ?
hyperopia
94
why are people longsighted ?
their lens is the wrong shape and doesn't refract the light enough or the eyeball is too short so the image of near objects are brought into focus behind the retina
95
how is long-sightedness fixed ?
by wearing glasses with a convex lens, where the lens curves outwards. The lens refracts so they focus on the retina
96
what is the name form short sightedness ?
myopia
97
why is short sightedness caused ?
the lens refracts light too much or the eyeball is too long so the image is brought to focus in front of the retina
98
how is short sightedness fixed ?
wearing glasses with a concave lens which curves inwards so light rays focus on the retina
99
what are contact lenses ?
thin lenses which sit on the surface of the eye and are shaped to fix the fault in focusing
100
what are the benefits of contact lenses ?
- lightweight
- basically invisible
- good for sports
101
what are the 2 types of contact lenses ?
hard lenses and soft lenses
102
what are the advantages and disadvantages of soft lenses ?
more comfortable but have a higher risk of eye infections
103
what is laser eye surgery ?
used to vaporise tissue changing the shape of the cornea
104
how does laser eye surgery help with short sightedness ?
slimming the tissue down makes it less powerful
105
how does laser eye surgery help with long sightedness ?
changing the shape so its more powerful
106
what is an advantage of laser eye surgery ?
the surgeon can precisely control how much tissue the laser takes off fully correcting vision
107
what is a disadvantage of laser eye surgery ?
risk to eye infections, or having a bad reaction to surgery
108
what is replacement lens surgery ?
long sightedness is treated by replacing the natural lens with a clear thin piece of plastic
109
what are the risks of replacement lens surgery ?
higher risks than laser eye surgery, can cause blindness
110
what is the thermoregulatory centre ?
acts as your own personal thermostat to monitor body temperature by balancing energy gained and lost
111
how does the thermoregulatory centre work ?
1. receptors in the thermoregulatory centre that are sensitive to the temperature of the blood flowing through the brain
2. receptors in the skin send information about skin temperature via nervous impulses
112
how is body temperature controlled ?
through a negative feedback system if it gets too high/low the body responds to bring the temperature back to optimum
113
how does the body respond to temperature changing ?
when temperature receptors detect core body temp has changed it sends impuleses to the thermoregulatory centre which processes information and automatically triggers effectors to help bring temp levels back to optimum
114
give examples of responses which reduce body temperature ?
- hairs on skin lie flat so less air is trapped near the surface of the skin so there isnt a layer of insulating air around the skin
-sweat is produced by sweat glands
-blood vessels supplying skin capillaries dilate so more blood flows closer to surface of skin which is called vasodilation which transfers energy to environment from skin
115
how does the body respond to heat up the body ?
- hairs on skin stand up to trap air
- no sweat produced
- vasoconstriction - blood vessels supplying skin capillaries get narrower to reduce blood which flows to surface of the skin
- shiver which transfers energy to warm body
116
what are hormones ?
chemical messengers which travel in the blood to activate target cells
117
where are hormones produced ?
endocrine glands
118
what does the endocrine system do ?
use hormones to react to changes in the environment or changes inside the body
119
what are the different glands in the endocrine system ?
pituitary gland
pancreas
thyroid
adrenal glands
ovaries
testes
120
pituitary gland -
produces many hormones which regulate body conditions these hormones act on other glands directing them to release hormones to bring about change
121
pancreas
produces insulin which is used to regulate the blood glucose level
122
thyroid -
produces thyroxine which regulates things like the rate of metabolism, heart rate, temperature
123
adrenal glands-
produces adrenaline used to prepae body for action
124
ovaries (females only)
produce oestrogen which is involved in the menstrual cycle
125
testes (males only)
produce testosterone which controls puberty and sperm production in males
126
compare nerves and hormones
nerves - fast action, act for a short period of time, act on a precise area
hormones- slower action, act for a long period of time, acts in a more general way
127
how does glucose level change in the day
- eating foods like carbs puts glucose into the blood from the digestive system
- metabolism of cells removes glucose from blood
- vigorous exercise reduces much more glucose from the blood
128
what controls glucose levels ?
pancreas
129
what does the pancreas do ?
produces different hormones which controls blood glucose level
130
what is insulin ?
a hormone which decreases blood glucose level when it gets too high
131
what happens when blood glucose levels gets too high ?
1. after eating carbs, blood glucose levels increase
2. pancreas detects this and produces insulin which is secreted into the blood
3. insulin causes more body cells to take up more glucose from the blood, cells in liver and muscles takes glucose and converts it into glycogen
4. this deceases blood glucose levels
132
what is glucagon ?
a hormone which increases blood glucose level
133
what happens when the blood glucose levels are too low ?
1. pancreas detects this
2. pancreas produces glucagon which is secreted into the blood
3. glucagon converts glycogen back into glucose which enters the blood
4. blood glucose levels rise again
134
what is type 1 diabetes ?
where a persons pancreas produces little to no insulin so their blood glucose levels rise dangerously
135
how can type 1 diabetes be treated ?
insulin therapy
limit intake of foods rich in simple carbs
regular exercise
136
what is insulin therapy ?
injecting insulin into the blood throughout the day, normally at meal times to make sure glucose is removed from the body quickly once food is digested
137
what effects the amount of insulin needed in insulin therapy ?
a persons diet, amount of exercise
138
why do people need to exercise regularly with type 1 diabetes ?
helps lower glucose levels as increased metabolism of cells during exercise removes more glucose from the blood
139
what is the disadvantage of insulin therapy ?
it cannot be controlled as accurately as a working pancreas so there may still be long term health problems
140
what is type 2 diabetes ?
where a person becomes resistant to their own insulin so their body cells don't respond properly to it
141
what can cause type 2 diabetes ?
obesity
142
how can type 2 diabetes be controlled ?
eating a carb controlled diet - avoids rises in glucose
regular exercise
143
what are modern treatment options for type 1 diabetes ?
pancreas transplant
144
what is a pancreas transplant ?
as they get a new pancreas with insulin being produced so people won't have to inject themselves with insulin again
145
what are the risks of a pancreas transplant ?
your body can reject the tissue, so you have to take immunosuppressive drugs which are expensive and have side effects
146
how is diabetes tested for ?
-1. urine samples, as a high blood glucose level can be tested by having a urine sample
2. blood test confirms the diagnosis as it is more reliable as it gives current level of blood glucose and can detect at a high level of glucose which urine samples can't
147
what do kidneys do ?
make urine out of waste products out of your blood
148
what is filtration in the kidneys ?
where substances filter out of the blood as it passes through the kidneys
149
what is selective absorption in the kidneys ?
where useful substances such as glucose, ions, and the right amount of water is absorbed back into the blood
150
give examples of substances which are removed from the body in urine
urea
excess ions and water
151
how do we lose water from the body ?
- from the skin in sweat
- from the lungs when we exhale
152
how is the amount of water in our body balanced ?
by the amount we consume and the amount removed by kidneys in urine
153
how are ions taken into the body ?
by food
154
what can happen if the ion content of the body is wrong ?
it could upset the balance between ions and water so too much or too little water is drawn up into cells by osmosis which can damage cells, and they don't work as well as normal
155
how can ions be removed from the body ?
in sweat
through the kidneys
156
what is deamination ?
excess amino acids are converted into fats and carbohydrates which can be stored
157
where does deamination occur ?
in the liver
158
what is a waste product from deamination ?
ammonia
159
what is ammonia converted to in the liver ?
urea
160
what are the structures in the kidney where filtration and selective reabsorption takes place called ?
kidney tubules
161
the more water that leaves the kidney tubules and is reabsorbed into the blood, the more what the urine is ?
concentrated
162
what does the anti-diuretic hormone ?
controls the cells in the kidney tubules, causing them to be more or less permeable to water so changing the volume of water which can be absorbed
163
how is ADH released into the blood stream ?
by the pituitary gland
164
what controls how much ADH is released into the blood ?
the brain
165
what controls water content regulation ?
negative feedback
166
describe what would happen in the body if water content is too high ?
1. receptors in the brain detects that water content is too high
2. coordination centre in the brain coordinates response
3. pitituary gland less ADH so kidney tubules become less permeable and less water is reabsorbed from kidney tubules
167
what happens if the receptors in the brain detects the water content is too low
1. coordination centre in brain coordinates a response
2. pitiutary gland releases more ADH so the kidney tubules more permeable and more water is reabsorbed from the kidney tubules
168
what happens if your kidneys don't work ?
waste substances build up in the blood and you lose your ability to control levels of ions and water in your body
169
how can kidney failure affect your body ?
affects your heart, bones, nervous system, stomach
170
how can you treat kidney failure ?
- dialysis
- kidney transplant
171
what is dialysis ?
where machines do the jobs of the kidneys
172
what is a kidney transplant ?
where the diseased kidney is replaced by a healthy one
173
what do dialysis machines do ?
take over the role of failing kidneys failing kidneys and filter the blood
174
how does a dialysis machine work ?
the persons blood flows alongside a partially permeable membrane surrounded by dialysis fluid
175
what does the partially permeable membrane in a dialysis machine do ?
allows things like ions and waste substances to go through, but not big molecules like proteins so useful dissolved ions and glucose won't be lost
176
what are the disadvantages of a dialysis machine ?
- not a pleasant experience and many have to have a dialysis session 3 times a week, which takes 3/4 hours
-can lead to infections and blood clots
- they have to limit the amount of fluid they take in as the kidneys play an important water content of the body , if they take in too much can increase blood pressure
- expensive
177
what is a kidney transplant ?
kidneys are transplanted from people who have died, and are organ donors or someone can donate a kidney
178
what are the issues with a kidney transplant ?
donor kidney can be rejected from the recipients immune system
179
why do kidneys get rejected ?
the antigens on the donor kidney is rejected by the recipients immune system so the recipients white blood cells attack the donor cells by producing antibodies
180
what precautions are taken to stop the donor kidney from being rejected ?
- a donor with a similar tissue type as the recipient is chosen
- treated with drugs with suppress the immune system which reduce the release of antibodies so the immune system won't attack the transplanted kidney
181
why is a donor with a similar tissue type used to donate a kidney ?
more similar tissue types reduce the chances of the recipients white blood cells from identifying the donors antigens as foreign and producing antibodies to attack the donor organ
182
what are the disadvantages of a kidney transplant ?
- long waiting lists
- even if a kidney has a matching tissue type, it may still be rejected
- suppressing immune system drugs can make recipient more vulnerable to other illnesses
- it is a major operation so can be risky
183
what are the benefits of kidney transplants ?
- reduces the hours spent on dialysis
- cheaper than long term dialysis treatment
184
what happens during puberty ?
your body starts releasing sex hormones that trigger secondary sexual characteristics
185
give examples of sexual characteristics ?
facial hair in men, breasts in women
186
what is the main reproductive hormone in men ?
testosterone
187
what is the main reproductive hormone in women ?
oestrogen
188
where is testosterone produced ?
testes
189
where is oestrogen produced ?
ovaries
190
what does testosterone do ?
stimulate sperm production
191
what does oestrogen do ?
involved in the menstrual cycle
192
what is the menstrual cycle ?
the monthly sequence of events in which the female body releases an egg and prepares the uterus in case it recieves a fertilised egg
193
what is the stages of the menstrual cycle ?
1. lining of uterus breaks down
2. lining of uterus builds up
3. egg released
4. lining of uterus maintained
- next cycle
194
what is stage 1 ?
menstruation (bleeding) starts, uterus lining breaks down, lasts 4 days
195
what is stage 2 ?
lining of uterus builds up again from day 4-14 into a thick spongy layer full of blood vessels ready for a fertilised egg
196
what is stage 3 ?
egg is released from ovary at day 14 - ovulation
197
what is stage 4 ?
wall is maintained for about 14 days until day 28, if no sperm has fertilised the egg the spongy lining breaks down and the cycle begins again
198
what are the 3 hormones used in the menstrual cycle ?
- follicle stimulating hormone (FSH)
- Luteinising hormone (LH)
- Oestrogen and progesterone
199
what is FSH ?
causes an egg to mature in one of the ovaries in a follicle and stimulates the ovaries to produce oestrogen
200
what is LH ?
stimulates the release of the egg at ovulation
201
what is oestrogen and progesterone ?
involved in the growth and maintenence of the uterus lining
202
where is FSH produced ?
pitituary gland
203
what does oestrogen do ?
stimulate the release of LH and inhibits the release of FSH
204
where is LH produced ?
pituitary gland
205
what does progesterone do ?
maintains the lining of the uterus in the 2nd half of the cycle
206
what happens when levels of progesterone falls ?
the lining breaks down
207
what does progesterone control ?
inhibits release of LH and FSH
208
what are contraceptives ?
used to prevent pregnancy
209
what hormones are taken to reduce fertility ?
oestrogen and progesterone
210
how does oestrogen reduce fertility ?
it prevents egg release, despite it helping stimulate the release of eggs
211
why does oestrogen reduce fertility ?
if it is taken every day, to keep the levels of it permenantly high, it inhibits FSH production and after a while egg maturation and egg release is stopped
212
how does progesterone reduce fertility ?
by stimulating production of thick cervical mucus prevents any sperm getting through and reaching an egg, it also reduces egg maturation and release of an egg
213
what are the benefits of using an oral contraceptive pill ?
- over 99% effective
- reduces risks of some types of cancer
214
what are the problems with using an oral contraceptive pill ?
- isn't 100% effective
- causes side effects like headaches, nausea, irregular menstrual bleeding, fluid retention
- doesn't protect against STDs
215
what is the skin patch ?
contains oestrogen and progesterone and is a small patch that's stuck to the skin which lasts a week
216
what is an implant ?
inserted under the skin at the arm, releases a continuous amount f progesterone which stops ovaries releasing eggs and makes it hard for sperm to reach the egg, lasts 3 years
217
what is the injection ?
contains progesterone, each does lasts 2-3 months
218
what are condoms ?
worn over the penis during sex and prevents sperm entering the vagina
219
what is a benefit of condoms ?
prevents you from STDS
220
what is a diaphragm ?
a shallow plastic cup which fits over the cervix to form a barrier
221
what does a diaphragm have to be used with ?
spermicide
222
what is spermicide ?
a substance which disabled sperm, but it is not very efffective as when used with a diaphragm
223
what is an intrauterine device (IUD)
a T shaped device that is inserted into the uterus to kill sperm and prevent implantation of a fertilised egg
224
what are the 2 types of IUDS ?
plastic IUDS - release progesterone
copper IUDS- prevents sperm surviving uterus
225
what is a surgical method of contraception ?
sterilisation
226
what is sterilisation ?
cutting or tying the fallopian tubes which connect ovaries to uterus or the sperm duct, tubes between testes and penis - permanent
227
what is a natural method to avoid fertilisation ?
finding out when in the menstrual cycle a woman is most and least fertile and avoiding sex when ovulating
228
what is the disadvantage to the natural method ?
unreliable and uneffective
229
why are natural methods popula ?
people thing barrier methods/contraception is unnatural
230
what is abstinence ?
not having sex - 100% effective
231
what hormones are taken to increase fertility ?
FSH and LH
232
why can low levels of FSH cause infertility ?
the levels are too low to help the egg mature and release
233
why are FSH and LH used to help make a woman get pregnant ?
they stimulate egg maturation and releases them from the ovaries
234
What are problems with using FSH and LH to get pregnant ?
- don't always work
- too many eggs could be stimulated causing twins, triplets
235
what is In vitro fertilisation (IVF) ?
a process used to help couples who have difficulty getting children
236
what are the stages of IVF ?
1. FSH and LH are given to the woman to stimulate eggs
2.Eggs are collected from womans ovaries
3. eggs are fertilised in lab using mans sperm
4. fertilised eggs grow into embryos
5. once formed 1 or 2 embryos are transferred to the womans uterus
237
why are more than 1 egg transferred to the womans uterus using IVF ?
to improve the chances of pergnancy
238
what are the cons of IVF ?
- multiple births could happen - risky for mothers and babies
- only 26% success rate in Uk = LOW
- physical and emotional stressful experience for mother, abdominal pain, dehydration,vomiting
239
how does advanced microscopy improve rates of IVF ?
- specialised micro tools, use on egg and sperm under microscope and remove single cells from embryos for genetic testing
- using time-lapse imaging means growth of embryos can be monitored to identify which are most likely to give a successful pregnancy
240
what are the social and ethical issues with IVF ?
- it results in unused embryos, people think embryos are human life
- testing embryos before implantation, people think it can lead to selection of preferred characteristics such as eye colour or gender
241
what is thyroxine ?
a hormone released by the thyroid gland
242
where is the thyroid gland ?
the neck
243
what does thyroxine do ?
regulate the basal metabolic rate
stimulating protein synthesis for growth and development
244
what is the basal metabolic rate ?
the speed at which chemical reactions occur while the body is at rest
245
when is thyroxine released ?
in response to thyroid stimulating hormone (TSH)
246
when the level of thyroxine in the blood is higher than normal what does the negative feedback system do ?
secretion of TSH is inhibited
this reduces the amount of thyroxine released from the thyroid gland
so the levels in blood falls back towards normal
247
when the level of thyroxine in the blood is lower than normal what does the negative feedback system do ?
secretion of TSH is stimulated
this increases the amount of thyroxine released from the thyroid gland
level in blood rises back to normal
248
what is adrenaline ?
a hormone released by the adrenal glands
249
where are the adrenal glands found ?
above the kidneys
250
when is adrenaline released ?
in response to scary or stressful situations
251
where does your brain detect fear or stress ?
your brain
252
what does your brain do when it detects fear ?
sends nervous impulses to the adrenal glands which secrete adrenaline
253
what does adrenaline do ?
gets the body ready for fight or flight by triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles
254
give an example of what adrenaline can do ?
increase heart rate
255
give examples of how plants can detect and respond to stimuli ?
- plants need light to make their own food - they can sense light and grow towards it to maximise light they recieve
256
what is auxin ?
a plant hormone that controls growth near the tips of shoots and roots
it controls the growth of a plant in response to different stimuli
257
what does auxin control ?
phototropism
gravitropism
258
what is phototropism ?
plant growth in response to light
259
what is gravitropism ?
plant growth in response to gravity
260
what is gravitropsim also known as ?
geotropsim
261
where is auxin produced ?
the tips of roots and shoots
262
how does auxin work ?
it moves backwards to stimulate the cell elongation process which occurs in the cells behind the tips
263
what could happen if the tip of a shoot is removed ?
no auxin is available so the shoot may stop growing
264
what does extra auxin do ?
promote growth in the shoot but inhibits growth in the root
265
what happens when shoots grow towards light ?
- more auxin accumulates on the side that is in the shade
this makes the cells grow faster on the shaded side so the shoot bends towards the light
266
what happens when shoots grow away from gravity ?
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
267
what means that a shoot should always grow in the right direction, even in the absence of light ?
the distribution of auxin in response to gravity
268
what happens to make roots grow towards gravity ?
when a root is growing sideways more auxin will accumulate on its lower side
in a root extra auxin inhibits growth
this means the cells on top elongate faster and the rot bends downwards
269
describe how to investigate the effect of light with the growth of cress seeds ?
1 - put 10 cress seeds in 3 different petri dishes each lined with moist filter paper
2- shine a light onto one of the dishes from above and 2 of the dishes from different directions
3- leave the cress seeds for 1 week to grow - the seedlings grow towards the light
270
what are the control variables when investigating the effect of light ?
- number of seeds
- type of seeds
- temperature
- water
- light intensity
271
describe how to investigate the effect of gravity on the growth of cress seeds ?
- put 4 cress seeds into a petri dish that is lined with damp cotton wool
- the roots of each seed should be facing in different direction
- store the petri dish vertically for a few days in the dark
- find that the roots of each seeds grow downwards and the shoots grow upwards because of gravity
272
what are auxins used for ?
killing weeds
growing cuttings with rooting powder
growing cells in tissue culture
273
how are auxins used for killing weeds ?
selective weedkillers are developed with auxins
they disrupt their normal growth patterns which soon kills them leaving grass and crops untouched
274
how are auxins used to grow from cuttings with rooting powder ?
if you add rooting powder which contains auxins to cuttings they will grow rapidly as new plants which enables clones of a really good plant to be grown quickly
275
what is a cutting ?
part of a plant that has been cut off
276
how do you use auxins to grow cells in tissue culture ?
auxins help stimulate cells to divide to form roots and shoots by adding them to the growth medium
277
what are gibberellins ?
a plant hormone which stimulate seed germination, stem growth and flowering
278
what are gibberellins used for ?
controlling dormancy
inducing flowering
growing larger fruit
279
how do gibberellins help to control dormancy ?
many seeds won't germinate until they have been through certain conditions - dormancy
seeds can be treated with gibberellins to alter dormancy and make them germinate at times they usually wouldn't
it helps make sure seeds in a batch germinate at the same time
280
how do gibberellins help inducing flowering ?
plants which require certain conditions to flower are treated with gibberellins so they will flower without any change in their environment
they also help grow bigger flowers
281
how do gibberellins help to grow larger fruit ?
if they are added to fruits they will grow larger
282
what is ethene ?
a gas produced by aging parts of a plant
283
what does ethene do in a plant ?
influence the growth of the plant by controlling cell division
stimulates enzymes which causes fruits to ripen
284
what is ethene used for ?
- to speed up ripening of fruits so they can be collected when they are unripe and less easily damaged - it is then added to the fruit at the supermarket so they are perfect to buy
285
how can the ripening of fruits be delayed ?
- adding chemicals which block ethene's effect on the fruit and reduce the amount of ethene fruit can produce
- chemicals are produced to react with ethene to remove it from air
