Homeostasis and Response Flashcards
1
Q
What is homeostasis?
A
The regulation of the conditions inside your body, to maintain a stable internal environment.
2
Q
Why is homeostasis important?
A
It regulates the conditions in your body,
- This is necessary for making sure your body is at the right temperature so enzymes work effectively,
- Your body temperature will change depending on the external environment, if it is cold your body will heat up to keep you from being warm,
- Your nerve and hormonal systems are also used to regulate your bodies conditions, such as blood sugar levels and oestrogen during a woman’s period.
3
Q
What are the three main components that work together to make up the automatic control systems?
A
- Receptors,
- Coordination centres (brain, spinal cord, pancreas),
- Effectors.
4
Q
What method does your automatic control system use when trying to keep your internal environment stable?
A
Negative feedback:
This counters the changes that your body experiences.
5
Q
How does negative feedback work?
A
- The receptor picks up a stimulus (levels of glucose in blood are too high),
- The coordination centre receives and processes the information than organises a response (knows that levels of glucose must decrease),
- The effectors produce a response, which counteracts the change and restores the optimum level (The level of sugar in the blood is reduced).
6
Q
What is a possible issue with the effectors?
A
They keep changing the conditions in your body until told other wise by a different stimulus from the receptors.
For example, if the blood sugar levels are too high, the effectors lower the levels, but may lower the levels of glucose in the blood to be too low, which is dangerous. Luckily the receptors pick up on differences in your body quickly so the effectors can keep your body at optimum conditions.
7
Q
What is the function of the nervous system?
A
To produce a reaction from your body after sensing a stimulus.
8
Q
What are the different parts of the nervous system?
A
- CNS (central nervous system),
- Sensory neurones,
- Motor neurones,
- Effectors.
9
Q
What is the CNS?
A
- Made up of the brain and spinal cord only, and is located mainly in the vertebrae of animals,
- The CNS is connected to the body by the sensory neurones and motor neurones.
10
Q
What is the Sensory neurone?
A
The neurones that carry information as electrical impulses from the receptors to the CNS.
11
Q
What is the motor neurones?
A
The neurones that carry electrical impulses from the CNS to effectors.
12
Q
What are effectors?
A
- They respond to nervous impulses and and bring about a response,
- All muscles and glands are an example of effectors,
- They respond to nervous impulses, for example, may cause muscles to contract or glands to secrete hormones.
13
Q
What are receptors?
A
- The cells that detect stimuli,
- There are loads of different receptors like taste and sound receptors on your tongue and in your ear respectively,
- Receptors can create large complex organs like the retina in the eye, the retina is covered in light receptors.
14
Q
What are the stages of the nervous system?
A
- Stimulus,
- Receptor detects the stimulus,
- The sensory neurone sends information from the receptor to the CNS using an electrical pulse,
- The motor neurone sends information from the CNS (decision from the CNS) to the effector using an electrical impulse,
- The effector carries out the instruction from the CNS,
- Then the muscle responds based on the effector.
15
Q
What is a synapse?
A
The connection between two neurones, it is a small gap where the two neurones connect.
16
Q
How does an electrical pulse travel across the synapse?
A
A pulse reaches the synapse (gap in between two neurones),
A chemical is released from the neurone with the impulse and the chemical diffuses across the synapse to the other neurone.
These chemicals then set off a new electrical impulse in the next neurone, identical to the one before.
17
Q
What are reflexes?
A
These are automatic reactions that your body does in response to a stimulus, this response and reaction does not happen within the conscious part of the brain.
18
Q
What is the main advantage of reflexes?
A
They prevent injury.
19
Q
What is a reflex arc?
A
The passage of information for a reflex to take place.
20
Q
What is the pathway of information for a reflex arc?
A
- Your receptors sense a stimulus,
- Information is sent from the receptors to the CNS via the sensory neurone,
- The sensory neurones electrical impulse travels across the synapse onto the relay neurone in the CNS,
- The impulse is then transferred across a synapse onto the motor neurone,
- The impulse then goes to the effectors and the muscles contract.
21
Q
Where is the relay neurone found?
A
CNS.
22
Q
What is the method for the ruler drop test/ reaction time?
A
- The person being tested should not have taken any caffeine, or drugs that will enhance performance before the test,
- The person should have their arm resting on the edge of the table, their index finger and thumb should be open, leaving a gap for the ruler to be dropped,
- A separate person should align the 0cm mark of the ruler with the top of the fingers,
- This person should drop the ruler with no warning, the person catching should try and catch the ruler in between their two fingers,
- The length on the ruler at their fingers is their reaction time in cm,
- This test should be done 3 times to take an average (mean),
- Then do the same with the performer drinking a fizzy drink/ caffeine before so their reaction time should increase,
- See the difference in reaction time, the second round should be a smaller distance/ quicker reaction time.
23
Q
What are other methods to test for reaction time?
A
computer tests:
- clicking a mouse when a stimulus appears,
- computers are more precise as software can be used to get the exact time in milliseconds,
- it is also completely random, the performer cannot predict when the dot will appear, unlike the ruler drop because body language can give it away.
24
Q
What are the three parts of the brain in the GCSE spec and what is their function?
A
> medulla - controls unconscious activity (breathing),
Cerebellum - responsible for muscular contractions,
Cerebral cortex - responsible for conscious things (intelligence, memory and language)
25
Where is the medulla located?
Near the spinal cord.
26
Where is the cerebral cortex located?
The top of the brain, the wrinkly part.
27
Where is the cerebellum located?
The bottom right of the brain, opposite the medulla.
28
What are the three methods used to study the brain?
- Studying patients with brain damage
- Electrically stimulating the brain,
- MRI scans
29
How does studying patients with brain damage help scientist to learn about the brain?
If there is a part of the brain which is damaged the body will be effected, you can then determine the role of this part of the brain by looking at the damage and change the person undergoes
30
How does electrically stimulating a part of the brain help scientists to learn about the brain?
When the brain is stimulated by an electrode placed on the tissue, something will happen, depending on what happened you can find out the function of the part of the brain that was stimulated.
For example, we now know that Parkinson's can be treated using electrical stimulation of the brain to prevent muscle tremors.
31
How does an MRI scan help scientists to learn about the brain?
An MRI scan makes a very detailed image and shows the activity of the brain, it can show what parts of the brain are active when doing certain tasks. For example, what part of the brain is used when trying to recall a memory or listening to music.
32
What are the risks of experimenting on brains?
- physical damage to the brain,
| - increased problems with a disorder (speech issues)
33
What is the scelra?
A tough supporting wall of the eye.
34
What is the cornea and its' purpose?
A transparent outer layer in front of the eye that refracts light onto the retina.
35
What is the iris and its' purpose?
The coloured part of your eye, it has muscles that control the diameter of the pupil, this controls the amount of light that can enter the eye at once.
36
What is the lens and its' purpose?
A convex tissue that is transparent, it focuses light onto the retina's light receptors.
37
What are the ciliary muscles and the suspensory ligaments and what do they do?
An antagonistic pair that controls the shape of the lens to bend light effectively.
38
What is the retina and its' purpose?
A group of light receptors at the back of the eye that receive light and turn the image into an electrical impulse.
39
What is the optic nerve and its' purpose?
A nerve at the back of the eye that carries impulses from the retina to the brain.
40
Why does the amount of light entering the eye have to be controlled?
Too much light onto the retina will damage it.
41
How does the iris control the shape of the lens?
Circular muscles contract and radial muscles relax when there is too much light, this constricts the pupil,
Circular muscles relax and radial muscles contract when here is too little light, this dilate the pupil.
42
Why does the pupil need to dilate and constrict?
> Dilate - to allow more light to enter the eye when there is little light,
> Constrict - to stop very bright/ a lot of light entering the eye and damaging the retina.
43
How do we focus on objects that are further away or closer?
The lens either becomes slimmer and taller, to focus the light a little (focus on far away object),
or gets fatter and shorter to focus the light a lot (focus on closer object).
44
How does the ciliary muscles and suspensory ligaments work together to help focus light?
```
When focusing on a close object:
- Ciliary muscle contracts,
- Suspensory ligament relaxes.
When focusing on a distant object:
- Ciliary muscles relax,
- suspensory ligaments contract.
```
45
Why are some people long sighted?
When someone is long sighted, their lens does not refract the light enough, therefore the light actually focuses behind the retina.
46
Why are some people short sighted?
When someone is short sighted, refracts the light too much, therefore the light actually focuses in front the retina.
47
How do you treat long sightedness?
You wear glasses with a convex lens.
48
How do you treat short sightedness?
You wear glasses with a concave lens.
49
How do you treat vision defects?
- Glasses
- Contact lens,
- Laser eye surgery,
- Replacement lens surgery
50
How do contact lens' work?
They are tiny lenses that sits on the surface of your eye to help bend the light correctly, They are very convenient for sports because they do not get in the way like glasses, they are also invisible and do not effect appearance.
51
what are the two types of contact lenses?
Hard lenses and soft lenses, soft lenses are mores comfortable but carry more risk of infection.
52
How does laser eye surgery work?
The tissue in the cornea is vaporised by a laser, making the cornea thinner, will help with short sightedness, changing the shape of the cornea will help with long sightedness.
However, there is a chance (like will all surgeries) the the eye could become infected during the procedure.
53
How does replacement lens surgery work?
The lens of the patient is removed and replaced by a transparent plastic lens, this will fix the vision of the patient.
However, since the surgery operate within the eye, there is a higher risk and chance of infection compared to laser eye surgery or contact lenses. The retina could also be damaged because the surgery operates inside the eye.
54
What part of our body is responsible for the regulation of temperature?
- There is a thermoregulatory centre in the brain which contains receptors that are sensitive to the blood temperature in the brain,
- Receptors in the skin also send signals to this part of the brain so that the thermoregulatory centre can act depending on the information it gets form the skin/ blood temp.
55
How does the thermoregulatory centre in the brain change the temperature in your body?
Using negative feedback.
56
Explain what happens when humans core temperature is too high?
- Temperature receptors pick up a high temperature,
- The thermoregulatory centre receives impulses from the receptors and instantly sends an impulse to the effectors to act on the increase in core heat,
- The effectors produce a response, e.g. sweat glands release sweat to cool down the body.
57
Explain what happens when humans core temperature is too low?
- Temperature receptors pick up a low temperature,
- The thermoregulatory centre receives impulses from the receptors and instantly sends an impulse to the effectors to act on the decrease in core heat,
- The effectors produce a response, e.g. muscles produce a response,
Some effectors work antagonistically, one muscle will heat up, while the other cools down in order to create an average temperature.
58
What methods does your body use to heat up?
- Hairs stand on end to trap in insulating layer of air (keeps the heat in),
- No sweat
- Blood vessels going to the skin constrict (vasoconstrict) to stop energy transferring from the blood vessels to the outside since the vessels are further away form the skin (shrunk)
- You shiver, muscle contractions need energy from respiration to keep you warm
59
What methods does your body use to cool down?
- You sweat, the sweat evaporates on your skin which transfers energy to the environment,
- Your blood vessels grow (vasodilate) and move closer to the surface of your skin so that more energy can be transferred from the hot blood to the environment.
60
What are hormones?
Regulatory substances produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action. Hormones tend to have quite long lasting effects.
61
What are 'target organs'?
The organ effected by a hormone.
62
Where are hormones produced?
Endocrine glands, they can be found all around the body.
63
What are all the glands called?
- The Pituitary Gland,
- Thyroid,
- Adrenal Gland,
- The Pancreas,
- Ovaries,
- Testes.
64
What is the function of the pituitary gland?
- Produces many hormones that regulate body conditions,
- Is sometimes referred to as the master gland because the hormones released often effect other glands, making hem release hormones.
65
What is the function of the Thyroid gland?
- Releases the hormone Thyroxine,
- This is involved in regulating metabolism rate, heart rate and temperature.
- Thyroxine is released from the Thyroid gland because the pituitary gland releases TSH (Thyroid stimulating hormone) to regulate these conditions.
66
What is the function of the Adrenal gland?
- Produces adrenaline in conditions of stress or fear, is used to prepare your body for 'fight or flight',
- Adrenaline increases the amount of oxygen and glucose going to muscles so that you can aerobically respire more and get out of situations by either running or using strength.
67
What is the function of the Pancreas in terms of hormone secretion?
- Releases insulin,
| - Used to regulate the glucose levels in the blood.
68
What is the function of the testes?
- Produces and releases testosterone,
| - Regulates puberty and sperm production in males.
69
What is the function of the ovaries?
- Produces oestrogen,
| - Involved in the menstrual cycle.
70
What are the difference between nerves and hormones?
- Nerves are very fast to react, while hormones are slower,
- Hormones last over a much longer duration, whereas, nerves act fro very short periods of time,
- Nerves act in a precise area, while hormones act in a general area.
71
Where is glucose used in the body?
- The normal metabolism of cells remove glucose form the blood (e.g. respiration),
- Vigorous exercises also remove glucose from the blood, again for respiration, but more glucose is removed when doing exercise,
- Excess glucose is turned in glycogen and is stored in the liver and in muscles for an easy supply for aerobic respiration.
72
How are the levels of glucose controlled when the levels are too high?
- Insulin is secreted by the pancreas into the glucose-concentrated blood,
- Glucose moves from the blood into the liver and muscle cells,
- The insulin makes the liver turn excess glucose into glycogen for storage,
- The glucose concentration in the blood is reduced.
73
How are the levels of glucose controlled when the levels are too low?
- Glucagon is secreted by the pancreas into the blood lacking glucose,
- Glucagon makes the liver turn stored glycogen into glucose,
- The liver releases the glucose into the blood,
- The glucose concentration in the blood increases.
74
How does type 1 diabetes effect glucose level regulation in the blood?
- Ppl with type 1 diabetes do not produce much insulin in their pancreas,
- This means that the glucose concentration in their blood can continue to rise with no stop,
- These ppl need insulin therapy, this involves multiple insulin injections throughout the day to artificially regulate the levels of glucose in the blood,
- They often need to be on a strict diet, avoid too much carbohydrates and do quite a lot of exercise, this limit the glucose in the persons blood.
75
How does type 2 diabetes effect glucose level regulation in the blood?
- When some1 has type 2 diabetes their body cells have become resistant to the insulin they produce,
- This means that the liver will not respond to the insulin and will not take in any glucose form the blood,
- So, glucose concentration in the blood can rise to dangerous levels,
- Type 2 diabetes is often caused by obesity,
- Type 2 diabetes can be controlled by avoiding lots of carbohydrates and also doing exercise.
76
How do the kidneys make urine?
- The kidneys take out unwanted and waste products from your blood,
- Substances are filtered out of the blood when it goes through the kidneys, this process is called filtration,
- Useful substances such as the right amount of water, some ions and glucose are absorbed back into the blood, this process is called selective absorption.
77
What substances are removed from the body in urine?
- Urea
- Water
- Ions
78
What is urea and why is released from the body in urine?
- Proteins cannot be stored in the body, so any excess amino acids must be converted to carbohydrates and fats for storage (process called deamination),
- Ammonia is produced as a waste product of deamination,
- Since ammonia is toxic, it is converted into urea in the kidneys and released from the body in urine.
79
Why are ions and water released out of the body in water?
- If there is too much water is in the body or too many ions, there will be an imbalance,
- If there is an imbalance, too much or too little water will be absorbed into cells via osmosis,
- So some ions and water must be released in urine to keep the perfect balance in your body.
- If there is the wrong amount of water in cells they wont work as effectively.
- Since we lose water from sweat and and in our skin, urine is the best way for us to control the amount of water in our body and keep the perfect balance.
80
What controls the water concentration urine?
- A hormone called Anti-Diuretic Hormone (ADH),
- The brain monitors the water level in the blood in order to releases the right amount of ADH to the blood,
- The whole process is controlled by negative feedback.
81
Why is kidney failure dangerous?
- If your kidney does not work properly, waste products will build up in your blood and you lose the ability to control the balance of ions and water in your body,
- This will eventually result in death.
82
How can people with kidney failure be kept alive?
- Dialysis treatment/ machines filter the blood,
| - Kidney transplant.
83
How do dialysis machines filter blood?
- Your blood goes through the dialysis machine,
- Your blood is surrounded in a partially permeable membrane with dialysis fluid is on the other side of the membrane,
- The dialysis fluid has the same concentration of ions and water as healthy blood,
- This means there is no concentration gradient when your blood has the perfect amount of ions and water so it stops diffusion,
- As the blood flows, waste products such as urea, water and ions diffuse out of the blood into the dialysis fluid.
- The blood then flows back into the patient and the dialysis fluid is released from the machine.
84
What are the disadvantages of dialysis treatment?
- It is expensive for hospitals to run,
- Many patients have to have treatment 3 times a week, each session is 3-4 hours,
- Can cause blood clots or infection,
85
What is the advantages of dialysis treatment?
It keeps the patient alive while they wait for a donor.
86
What are the pros and cons of kidney transplants?
Pros:
- They are the only current cure for kidney failure,
- They are cheaper than dialysis in the long term,
Cons:
- The kidney can be rejected by the patients body,
- A sufficient donor needs to be found,
- There are long waiting lists for kidney donors.
87
How do people donate a kidney?
- They need to register to be a donor or carry a donor card,
| - They can be alive or dead but must be registered.
88
What are the two main reproductive hormones?
- Testosterone in males,
| - Oestrogen in females.
89
What is the menstrual cycle?
A 28 day cycle when a woman releases an egg to mature in preparation for pregnancy.
90
What are the 4 stages of the menstrual cycle?
- Menstruation starts (Day 1-4),
- The uterus lining builds up again (Day 4-14),
- Ovulation (Day 14),
- The wall is then maintained (Day 14-28).
91
What happens in the first stage of the menstrual cycle?
The uterus lining sheds for about 4 days.
92
What happens in the second stage of the menstrual cycle?
The uterus lining builds up again from day 4 to 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg.
93
What happens in the third stage of the menstrual cycle?
An egg develops and is released form the ovary at day 14, this is called ovulation.
94
What happens in the fourth stage of the menstrual cycle?
The wall is then maintained from days 14 to 28, if no fertilised egg lands on the uterus, the wall sheds again and the cycle restarts.
95
What are the hormones that control the menstrual cycle?
- Oestrogen
- FSH (follicle stimulating hormone),
- LH (Luteinising Hormone),
- Progesterone
96
What is the function of oestrogen?
- Produced in the ovaries
- Causes the lining of the uterus to grow,
- Stimulates the release of LH and inhibits release of FSH.
97
What is the function of FSH?
- Produced in pituitary gland,
- Causes an egg to mature in one of the ovaries, in a structure called a follicle,
- Stimulates the ovaries to produce oestrogen.
98
What is the function of LH?
- Produced in the pituitary gland,
| - Stimulates the release of an egg at day 14.
99
What is the function of Progesterone?
- Produced in the ovaries by the remains of the follicle after ovulation,
- Maintains the lining of the uterus during the second half of the cycle,
- Inhibits the release of LH and FSH.
100
When is Oestrogen present in the menstrual cycle?
- Present in between day 4 and roughly day 16.
| - When the uterus wall builds up.
101
When is Progesterone present in the menstrual cycle?
- Present in between day 14 and 28,
| - When the uterus wall is maintained.
102
When is FSH present in the menstrual cycle?
- Constantly present at quite a high quantity,
- Dips a tiny bit in between days 4 and 14,
- Then peaks when the egg is released and raises slightly until the end of the cycle.
103
When is LH present in the menstrual cycle?
- Constantly present at quite a high quantity,
| - Peaks a lot when the egg is released at day 14.
104
What is the combined pill?
- A pill containing Oestrogen and Progesterone,
| - Has over 99% effectiveness to stop fertilisation.
105
What is the alternate pill that is not combined?
- A pill only containing progesterone,
- Also has over a 99% effectiveness to stop fertilisation,
- has less side effects than the combined pill.
106
Why can oestrogen be used to stop the release of the egg?
- Constant Oestrogen inhibits the production of FSH which stimulates the production of the egg,
- If no FSH is present no egg can be released.
107
Why can progesterone be used to stop fertilisation?
- Stimulates the production of mucus and prevents the sperm from getting to the egg and penetrating.
108
What are the hormonal contraceptive methods?
- The pill,
- The combined pills,
- contraceptive patch,
- Contraceptive implant,
- Contraceptive injection,
- Intrauterine device (IUD).
109
How does the contraceptive patch work?
- A patch witch releases Oestrogen and Progesterone,
- It's a 5cm X 5 cm patch installed under the skin
- Each patch lasts 1 week.
110
How does the Contraceptive implant?
- Is inserted under the skin of the arm,
- It releases a continuous amount of progesterone which stops the release of the egg, the implant of an egg in the vag, and produces.
- Each implant lasts 3 years
111
How does the contraceptive injection work?
An injection of progesterone that lasts 2-3 months.
112
How does the intrauterine device (IUD) work?
- A T-shaped device inserted into the uterus to kill sperm and prevents implantation of a fertilised egg.
113
What are the two types IUDs?
- Plastic IUDs that release copper and progesterone,
| - IUDs that prevent the sperm from servicing.
114
What are the barrier methods of contraception?
- Condoms,
- Diaphragm,
- Spermicide,
- Femidom.
115
How do barrier methods of contraception work?
They stop sperm from meeting the egg.
116
How does a diaphragm work?
- A shallo plastic cup that fits over the cervix to form a barrier,
- It has to be used with spermicides.
- Is 94% effective when used perfectly.
117
How does spermicide work?
It kills or deactivates the sperm.
118
What is a vasectomy?
- Cutting or tying the Fallopian tubes (connects the ovaries to the uterus) in a female or the sperm duct in a male (connecting the testes and penis),
- This is a permanent procedure and makes you infertile,
- There is a very small chance the tubes can rejoin tho.
119
What are the natural methods to prevent impregnation?
- Good pull out game,
- Avoiding shagging when your yats egg could be most fertile,
- Abstinence, no shagging at all.
120
How can women with insufficient amounts of FSH mature their eggs?
- Inject themselves with FSH and LH to stimulate ovulation.
121
What are the pros and cons of receiving LH and FSH and a woman to help with fertility?
Pros:
- It helps woman to get pregnant,
Cons:
- It doesn't always work, so can expensive.
- Too many eggs can be stimulated meaning unexpected pregnancies (twins/ triplets.)
122
What is IVF (in vitro fertilisation)?
- Extracting eggs from a woman and fertilising them in a lab using the mans sperm.
- When the egg is fertilised, it is incubated as an embryo in the laboratory incubator,
- Once the embryos are tiny balls of cells, they are transferred back into the woman uterus so that there is a higher chance of pregnancy.
123
What is intra-cytoplasmic sperm injection (ICSI)?
Where the sperm is extracted from a man and injected into the egg of a woman, it is useful if the man has low sperm production.
124
What hormones are given to a woman to allow eggs to mature and be released for the extraction of an egg for IVF?
LH and FSH
125
What are the pros and cons of IVF?
Pros:
- Can allow pregnancy for infertile couples.
Cons:
- High risk of miscarriage if more,
- Success rate is low, makes the procedure depressing,
- Some women have strong reactions to he hormones, abdominal pain, vomiting, dehydration.
126
What effect does an advancement in microscopy techniques have on IVF?
The pregnancies are more likely to be successful.
127
Why are some people against IVF?
- When pregnancies are unsuccessful, the embryos are wasted, this kills potential human life,
- The genetic testing also raises ethical questions about making a perfect child (gender and eye colour etc.)
128
What is auxin and where is it located?
A plant hormone that controls growth, it is located at the tips of shoots and roots.
- Auxin responds to light and gravity and grows depending on the conditions.
129
How does auxin stimulate growth?
It is made in the tips of roots and shoots and moves backwards, down the root or shoot and stimulates cell elongation just behind the tips.
130
What happens if the tip of a root or shoot is removed?
There can no longer be growth in that root or shoot.
131
What happens when there is an abundance of auxin?
It promotes growth in shoots but inhibits the growth in the root.
132
What direction to shoots grow when light is present?
The auxin moves away from the light and causes the shoot to curve towards the light by only growing the underside of the shoot.
133
What way do shoots grow compared to gravity?
- Gravity pulls the auxin down,
- This causes an imbalance of auxin in the shoot,
- because growth is encouraged in shoots, the bottom begins to grow faster,
- The bottom of the shoot grows faster and curve upwards.
134
What way do roots grow compared to gravity?
- Gravity pulls the auxin down,
- This causes an imbalance of auxin in the shoot,
- The bottom of the shoot grows slower because auxin inhibits growth in root,
- This curves the root downwards because the top of the root grows faster.
135
How can you investigate plants growth responses to light?
- Put 10 cress seeds in separate petri dishes, each lined with moist filter paper,
- Each petri dish should have a lamp shining light on it, each one facing a different direction,
- Leave the seeds to grow for 1 week,
- You will see the seeds would have grown and faced towards the light.
136
What are the commercial uses for auxins?
- Killing weeds (Auxins can kill plants with very broad leaves),
- Growing from cuttings with rooting powder (The root powder allow the cuttings to grow back when placed),
- Growing cells in tissue culture (can be used to grow clones).
137
What are the commercial uses for Gibberellin?
- Controlling dormancy (allows plants to germinate at times of the year when not in season),
- Inducing flowering (they flower without any changes in the environment),
- Growing larger fruit (gibberellin is added to fruits that are forced to grow without seeds so they are as big as the normal fruits with seeds).
138
What are the commercial uses for Ethene?
- Ethene influences the growth of the plant by controlling cell division, it also stimulates enzymes which ripen the fruit.
- These fruits can be picked while they are unripe and can be ripened when its on the way to the super market,
- The effects of ethene can also be delayed so they are the perfect ripeness when on the shelf to be bought.
139
What are the three ways our body loses water?
- Exhaling,
- Sweating,
- Urinating.
140
How does the kidney create Urine?
- Arteries diffuse substances such as glucose, ions, water and urea into the tubules of the kidney,
- Then important substances are selectively reabsorbed back into the blood (glucose, water and ions),
- Urea, excess water and excess ions are left in the kidneys and form Urine,
- This is then sent to the bladder for a fat wazz.
141
How does the body increase the water concentration in blood?
- When water levels are too low, ADH (anti-diuretic hormone) is released by the pituitary gland and goes to the kidney,
- The tubules in the kidney becomes more permeable because of the ADH,
- So more water can be reabsorbed from the tubules back into the blood,
- The pituitary gland stops releasing ADH when the blood water concentration is optimum,
- This is a negative feedback cycle.
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What happens if the blood is too dilute?
- The pituitary gland releases less ADH,
| - So the tubules do not become more permeable so less water is released back into the blood and is peed out in urine.
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What is phototropism?
When plants grow towards the light.
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What is geotropism?
When shoots grow towards the force of gravity.
