This page contains the GCSE AQA Biology Homeostasis in action Questions and their answers for revision and understanding Homeostasis in action.
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Answer:
it is important that core body temperature is around 37°C and does not rise above 40°C or fall below 35°C because if few degree above or below normal body temperature than enzyme do not function properly.
2 Explain the role of:
Answer:
Temperature receptors in the skin detect changes in the external temperature. They pass this information to the processing centre in the brain, called the hypothalamus.
The processing centre also has temperature receptors to detect changes in the temperature of the blood. The processing centre automatically triggers changes to the effectors to ensure our body temperature remains constant, at 37°C.
Answer:
The effectors are sweat glands and muscles.
If we are too hot or too cold, the processing centre sends nerve impulses to the skin, which has two ways to either increase or decrease heat loss from the body’s surface.
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Birds are warm-blooded and have a higher metabolism and body temperature than humans. The average bird’s body temperature is 40° Centigrade although this will fluctuate during the day depending on climate and activity. It can therefore be a challenge for birds to maintain this high temperature when temperatures fall sharply. Small birds are most at risk as they have a proportionally larger surface area on their bodies.
The main insulation against the cold are feathers. Many species of birds grow extra feathers during the late autumn to give them more protection during the winter. The oil that coats their feathers provides another layer of insulation as well as help keep them protected from water. During cold weather you may see birds that appear to be fatter than usual – they are in fact fluffing their feathers to trap warm air beneath them.
Birds’ legs and feet are covered in scales that minimise heat loss. They are also able to constrict blood flow to their extremities which reduces heat loss further. You may see birds standing on one leg in the cold or crouched over to cover both legs with feathers. They are also able to tuck their bills into the feathers at their shoulders.
Most birds will build up fat reserves before the winter which provides extra insulation and energy for generating body heat. During the autumn food is abundant and you will often see birds gorging on berries, insects and from bird feeders.
On sunny days during the winter birds will turn their backs to the sun and raise their feathers to absorb the maximum solar heat. They may also droop their wings and spread their tails. On very cold days they will shiver to raise their metabolic rate and generate more body heat. Shivering is an effective but short term way to stay warm.
In the winter you may see large flocks of birds gathered together in small spaces to share body heat. They will roost in shrubs and trees, empty bird houses and other spots that have residual heat from the day’s sunlight.
Answer:
Core temperature in horses is normally regulated within narrow limits. Information from thermal receptors in the skin and internal organs are integrated in hypothalamus, which is the dominant controller over body temperature. Horses are found at ambient temperatures from – 40 to 40°C. Depending on management routines, breed and activities horses may grow a thick winter coat. In cool-acclimated horses at rest the lower critical temperature of the environment has been reported to be – 15°C. In horses kept in stables at night and not acclimatized to winter climate the lower critical temperature has been estimated to 5°C
Horses have a high metabolic capacity combined with a small surface area for dissipation of heat. When horses exercise about 20% of the metabolism in the muscle cells is used for work and the remaining 80% becomes heat. Skin blood flow increases during internal body heating transferring the heat from body core to the surface of the skin and if vasodilatation is not sufficient sweating starts.
Horses adapted to cool winter climate exercising in a climatic chamber at temperatures ranging from 5 to 18°C showed more efficient evaporation after they had been clipped than comparable experiment with winter coat intact.
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water is lost from the body through the skin by perspiration, kidneys by urine, lungs by breathing out water vapor
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urea is nitrogenous waste product produce from the breakdown of amino acids.
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Removing waste products. Waste products must be removed from the body. If they are not, they will increase in concentration and may interfere with chemical reactions or damage cells. Waste products that must be removed include carbon dioxide and urea.
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Deamination of amino acids results in the production of ammonia (NH3). Ammonia is an extremely toxic base and its accumulation in the body would quickly be fatal. However, the liver contains a system of carrier molecules and enzymes which quickly converts the ammonia (and carbon dioxide) into urea.
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The kidneys are important for Excretion and Homeostasis.
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Kidneys filter the blood. Glucose, mineral ions, urea and water all move out of our blood in to the Kidney.
The blood cells and large proteins are too big to leave the blood in the filtering process – they do not go into the kidney tissues.
All the blood in our body passes through our kidneys about once every five minutes .Our kidneys filter about 180 litres of water out of your blood during the day.
About 99% of it is returned straight back into your blood. On average, you produce about 1800cm3 of urine a day.
Urine trickles into our bladder where it is stored. When the bladder is full, you will feel the need to empty it.
All of the glucose is reabsorbed back into the blood by diffusion and active transport. However, the amount of water and dissolved mineral ions that are reabsorbed varies. It depends on what is needed by your body. This is known as selective reabsorption.
3 Look at Figure 3.
a Describe what the data tells you. [4 marks]
4 Explain how ADH stimulates your kidneys to maintain the water balance of your blood on:
Answer
Kidney failure is a process of decline of kidney function, which usually develops very slowly (except acute kidney failure). Due to decrease of kidney function, kidney can’t filter wastes and fluids out of body. Consequently, many wastes and fluids deposit in body and many complications of kidney failure appear, which is very harmful for patients with kidney failure.
Answer
Dialysis depends on the processes of osmosis and diffusion.
The toxins are filtered through a semipermeable membrane. They are filtered out through diffusion because there is a difference in the concentration of toxins (and other solutes) on each side of the semipermeable membrane. These solutes naturally move through the membrane from areas of high concentration (the blood) to areas of low concentration (the dialysate or filtering fluid)
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A dialysis machine tries to mimic some of the functions of a human kidney. One of the primary jobs of a kidney is to remove urea and certain salts from the blood so they can exit the body in urine.
In a dialysis machine, blood from the patient runs through tubes made of a semi-porous membrane.
Outside the tubes is a sterile solution made up of water, sugars and other components.
Red and white blood cells and other important blood components are too large to fit through the pores in the membranes, but urea and salt flow through membranes into the sterile solution and are removed.
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There is no active transport. Someone on dialysis has to control their protein intake carefully between sessions to keep urea levels low. They also have to control the amount of salt they eat as their kidneys cannot get rid of excess mineral ions.
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No people on dialysis must follow a strict diet. This includes fluid intake. The dialysis doctor together with a nutritionist will give you your daily amount of fluid intake allowed in a day. The diet is called a renal diet…..the main thing about the diet is not allowed to eat any processed food. And limit salt intake usually. These diets are important to follow because the kidney’s filter out the toxins in the body and if they are not working properly the toxins go into the bloodstream. That is why people go on dialysis when there kidney’s fail
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This allows a large concentration gradient, allowing masses of urea to diffuse and create safe levels of urea in the blood. However, normal levels of other substances creates a small diffusion gradient, stopping diffusion which may cause too much to be taken out of the blood – causing danger.
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These fluids must be in constant circulation to prevent the growth of microbes. If the fluids are allowed to stand still, bacteria will grow in them, possibly causing sepsis for the patient.
If by dialysis fluids, you mean the dialysate (filtering fluid) and blood during a dialysis treatment:
They must be in constant circulation so that new blood is constantly passing through the filter to remove the toxins. If the fluids were not in motion, only a very tiny portion of the blood would be cleaned, defeating the purpose of the treatment.
Answer
The person have to take immunosuppressant drugs every day for life, although these are improving.This helps to prevent the rejection of their new organ
The person need regular checkups for signs of organ rejection.
2 Sometimes a live donor, often a closely related family member, will donate a kidney. These transplants have a higher rate of success than normal transplants from dead, unrelated donors.
Answer
Since the make-up of the body within families can be similar; or more rarely – as in the case of identical twins – the same, the likelihood of the recipient’s body rejecting the new kidney, is smaller. Therefore, there is a greater chance of a successful kidney transplant if the kidney is donated by a family person as the chances of matching tissues are higher.
Answer
One of the most frequent concerns of potential living kidney donors is whether the loss of one kidney will hamper them in later life. A healthy person can live a completely normal life with only one kidney, indeed, some people are born with only one kidney.
The operation to remove a healthy person’s kidneys is – as far as their own body is concerned – not of any direct benefit. Although all possible precautions are taken, there is always a small risk when undergoing surgery.
Other reason is the tissue mismatching .
Answer
Dialysis is much more readily available than donor organs, so it is available whenever kidneys fail. It enables people with kidney failure to lead a relatively normal life. However, you are tied to a special diet and regular sessions on the machine.
Long-term bladder dialysis is much more expensive than a transplant, and eventually dialysis causes serious damage to the body. If you receive a kidney transplant, you are free from the restrictions that come with regular dialysis sessions. You can eat and drink what you want. An almost completely normal life is the dream of everyone waiting for a kidney transplant. The disadvantages of transplants are mainly to do with the risk of rejection. You have to take immunosuppressant drugs every day for life, although these are improving. You need regular checkups for signs of organ rejection. The biggest disadvantage is that you may never get a transplant.
Answer
maintenance of internal conditions within narrow limits
Answer
Optimal cell function requires correct temperature so enzymes work optimally,
correct concentration of water and mineral ions in blood so osmosis doesn’t cause cell damage,
glucose for respiration to provide ATP,
and removal of waste products as build-up can change pH or poison systems.
2 Negative feedback is involved in many different aspects of homeostasis. For each of the scenarios below, explain how the human body would respond.
Answer
Pituitary gland releases less ADH,
kidney tubules reabsorb less water,
more urine produced,
water levels fall.
Answer
Thermoregulatory centre sends impulses,
capillaries constrict,
sweating reduced,
body hairs raised,
temperature rises.
Answer
Pancreas releases glucagon,
glycogen broken down to glucose,
amino acids broken down,
blood glucose rises.
Answer
Deaths increased,
first gradually and then by a lot.
Answer
Around 25 °C.
Answer
people lose lots of water by sweating, become dehydrated and can’t sweat more to cool down; exercise in high temperatures causes heating from respiration in muscles; temperature regulation less efficient in small children and the elderly; high humidity prevents cooling by sweating, increasing body temperature.
4 Sometimes kidneys fail. Two ways of treating kidney failure are the use of a dialysis machine and kidney transplants.
Answer
Kidneys remove urea and other toxins so levels do not build up and poison cells, and balance levels of water and mineral ions in body fluids to prevent osmotic damage to cells.
Answer
Blood passes between dialysis membranes
where excess salt and urea are removed by diffusion down a concentration gradient into dialysis fluid,
which contains no urea and normal plasma levels.
Answer
Any two advantages from:
no need for regular dialysis, no need for controlled diet, can live normal life.
Any two disadvantages from:
have to take immunosuppressant drugs for life, may reject kidney, limited transplant lifespan.
Answer
dialysis: 36%,
transplant: 82%
Answer
Transplant.
Not enough donor organs from dead or living donors,
can’t always get tissue match for patient.
01 There are temperature receptors in the body that detect the air temperature, and others that detect the temperature of the blood.
Answer
(air temperature) skin
(blood temperature) thermoregulatory centre
01.2 If the body temperature is outside the normal range, the body responds to restore a normal temperature.
Describe the changes that occur when the temperature is too high.
Answer
examples of the points made in the response
if body temperature is too high:
vasodilation
to increase blood flow to skin
to increase energy transfer to surroundings
sweat produced
evaporation causes cooling
hairs lie flat against skin
to reduce insulation
so energy can escape
02 Carbon dioxide, mineral salts, and urea are three substances that are excreted by the body.
Answer
carbon dioxide – lungs
mineral salts – skin / kidneys
urea – kidneys / skin
02.2 Another excretory product is water.
Water can be lost from the body in breath, faeces, sweat and urine.
Figure 1 shows the percentage of water lost from the body in these four substances on a cold day.
Answer
13 (%)
Answer
for cooling (the body)
or
to maintain body temperature
Answer
less water would be lost in urine
Answer
protein
02.6 Some people with kidney failure are treated by dialysis. Other people with kidney failure have a kidney transplant.
In dialysis treatment the blood is filtered through a machine.
A kidney transplant is more cost effective than dialysis treatment.
The cost of one kidney transplant operation is £20000. After a kidney transplant the patient has to take drugs to make sure the kidney is not rejected by the body. The drugs cost £5000 per year.
Answer
£70 000
Answer
£230 000
Answer
any one from:
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References:
BBC Bitesize
AQA GCSE Science Kerboodle textbook
Wikipedia
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This page contains the detailed and easy notes for AQA GCSE Biology Cell Biology for revision and understanding Cell Biology.
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Homeostasis is important for the enzymes as the enzymes control all the reactions of the body and they need optimum condition to work.
Motor Neurone
Sensory Neurone
Relay Neurone
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Example: Knee Jerk Reflexes,
|
| Sensory neurones |
Motor neurones
CEREBRUM (Cerebral Hemisphere) – It is nearly 80% part of the brain
CEREBELLUM – It lies behind the cerebrum and above the medulla oblongata. It is the second largest part of brain and is highly convoluted area which accommodates many neurons.
MEDULLA OBLONGATA or oblong marrow is oblong cylindrical part of the brain. It forms the hindermost part of the brain.
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Magnetic Resonance Imaging (MRI) helps to take the Images of different parts of the brain and relating it with loss of functions of the individual
Problems
For distant vision, ciliary muscle relax making the suspensory ligaments tensed which inturn make the lens thin so that the image is focussed on the retina.
For near vision, ciliary muscle contract making the suspensory ligaments to slack which inturn make the lens thick so that the image is focussed on the retina.
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MYOPIA
HYPERMETROPIA
Contact Lenses
Laser Surgery
Replacement Lens
Hormones
Nervous System
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EXAMPLES
| GLAND | HORMONE | TARGET ORGAN | EFFECT |
| Pituitary | Follicle stimulating hormone (FSH) Thyroid stimulating hormone (TSH) Anti-diuretic hormone (ADH) | Ovaries Thyroid Gland Kidneys | make the female sex hormones estrogen stimulate the gland to release thyroxine which control metabolism controls the water level by causing reabsorption of water |
| Thyroid Gland | Thyroxine | Liver and Kidneys | Controls the metabolism |
| Adrenal Gland | Adrenaline | Liver and Heart | prepares for fight and flight |
| Testes | Testosterone | Male reproductive organs | Developes secondary sexual characterstics |
| Pancreas- | Insulin Glucagon | Liver Liver | Decreases blood glucose levels Increases blood glucose levels |
| Ovaries | Oestrogen Progesterones | Female reproductive organs | Controls the development of egg, menstural cycle and develop secondary sexual characteristics. |
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Glucagon ‘is the hormone
Glycogen is the stored carbohydrate
| TYPE 1 | TYPE 2 |
| Insulin dependent | Insuline independent |
| Body does not produce insulin | Body is resistance to insulin |
| Caused by damage to pancreas | Caused by poor lifestyle and diet |
| Treated with insulin injections | Treated with lifestyle changes |
| Most common in young age | Common in obese people |
| It can be genetic. | It is mostly environmental. |
| Drugs might not be required | Drugs are given to make body to respond to insulin |
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TYPE 1
TYPE 2
FIGHT OR FLIGHT HORMONE
Emergency Hormones
HUMAN REPRODUCTIVE SYSTEM
Male hormone responsible for secondary sexual characters
Female hormone responsible for secondary sexual characters
| Days | Phase | Development |
| Day 1- Day 4 | Mensturation | Shedding of the uterus linning along with the egg. Progesterone falls |
| Day 5- Day 14 | Follicular Phase | Egg is matured in the ovary. Increase in FSH |
| Day 14 | Ovulation | Egg is released. Caused by Lutenizing Hormone |
| Day 14-Day 28 | Luteal Phase | Increase in progesterone and oestrogen which maintains the uterus linning and wait for eggs to fertilize. If not fertilize in next 14 days linning breaks. |
HORMONES OF MENSTURATION
| Hormone | Gland | Effective Days | Effect |
| Follicle Stimulating Hormone (FSH) | Pituitary | Day I-Day 14 | Maturation of egg in the follicle. Stimulate the production of Oestrogen |
| Lutenizing Hormone (LH) | Pituitary | Day 14 | Cause Ovulation |
| Oestrogen | Ovaries | Day 14-Day 28 | Develops uterus lining. Stimulates LH and inhibit FSH |
| Progesterone | Empty egg follicle in the ovaries | Day 14- Day 28 | Maintains linning of uterus and prepare for pregnancy. Inhibits both LH and FSH So no mensturatlon happen during pregnancy. |
Preventing Sperms to reach the egg. Preventing the implantation of the zygote in the uterus.
Barrier Methods: Prevent the sperm to meet the eggs
Hormonal Methods: Prevents the eggs to mature or prevent the implantation of eggs in the uterus.
Chemical Methods: Kills the sperm
Intrauterine Device: Prevent embryo from implanting
Surgical Method: It is permanent contraception
Contraceptive Pills
Contraceptive Pills
Intra Uterine Device
Surgical Methods
VASECTOMY: Male Sterlization
TUBECTOMY: Femal Sterlization
OVULATION PROBLEM
FAULTY TUBES
IMPLANTATION
PREGNANCY DEVELOPMENT
IN VITRO FERTILIZATION
Fertility drugs to stimulate ovulation
Ovary and sperm are collected to perform fertilization.
Fertilized egg is developed in the laboratory giving suitable conditions to develop into an embryo.
Embryo is inserted into the uterus
Develops into a baby.
Plant Hormones
Auxin is produced in the shoot tip. When light falls on auxin it is displaced to the shader side promoting growth of the shader region resulting in growth of shoot towards light.
Gravitropism – The movement of roots towards gravity.
AUXINS
GIBBERLINS
ETHENE
Cytokinin
Caused Cell Division
Abscicic acid
Stress hormone prepared the plant for stress conditions
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The products produced during metabolic reactions like respiration, digestion etc.
Carbon Dioxide
Water
Urea
ULTRAFILTRATION
SELECTIVE REABSORPTION
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Advantages
Disadvantages
Advantages
Disadvantages
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Make sure you have watched the above videos and are familiar with the key definitions before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.