Topic 5- Homeostasis and Response Flashcards
What is homeostasis?
It is all about the regulation of the conditions inside your body (and cells) to maintain a stable internal environment, in response to changes in both internal and external conditions.
Give 2 automatic control systems that regulate your internal environment.
Nervous and hormonal communication systems.
Give 3 examples of what automatic control systems control.
- Body temperature
- Blood glucose
- Water content
Give 3 examples of what automatic control systems control.
- Body temperature
- Blood glucose
- Water content
Give 3 main components your automatic control systems are made up of.
- Receptors
- Coordination centres
- Effectors
Give 3 examples of coordination centres.
- Brain
- Spinal cord
- Pancreas
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Name the mechanism used by automatic control systems to keep your internal environment stable.
Negative feedback
Give 2 examples when your body uses negative feedback.
When the level of water or temperature gets too high or too low.
What is a stimulus?
A change in the environment.
What does your body do if the level of something is too high? (1)
Receptor detects a stimulus- level is too high.
What does your body do if the level of something is too low? (2)
The coordination centre receives and processes the information, then organises a response.
What does your body do if the level of something is too high? (2)
The coordination centre receives and processes the information, then organises a response.
What does your body do if the level of something is too high? (3)
Effector produces a response, which counteracts the change and restores the optimum level- the level decreases.
What does your body do if the level of something is too low? (1)
Receptor detects a stimulus- level is too low.
Why do the internal conditions of your body need to be regulated?
Your cells need the right conditions in order to function properly, including the right conditions for enzyme action.
What does your body do if the level of something is too low? (3)
Effector produces a response, which counteracts the change and restores the optimum level- the level increases.
Why do the effectors carry on producing the responses?
They’re stimulated by the coordination centres.
What is the problem with effectors producing the responses for too long?
It changes the level too much (away from the ideal).
What does the CNS consist of in vertebrates?
The brain and spinal cord only.
What happens if the effectors change the level too much?
The receptor detects if the level becomes too different and negative feedback starts again.
What are the 4 main parts of the nervous system?
- Central Nervous System (CNS)
- Sensory neurones
- Motor neurones
- Effectors
What does the nervous system allow?
It allows humans to react to their surroundings and coordinate their behaviour.
What are vertebrates?
Animals with backbones.
What is the CNS connected to in mammals?
It is connected to the body by sensory neurones and motor neurones.
What are sensory neurones?
The neurones that carry information as electrical impulses from the receptors to the CNS.
What are motor neurones?
The neurones that carry electrical impulses from the CNS to effectors.
What are effectors?
They are all your muscles and glands, which respond to nervous impulses.
What are receptors?
They are cells that detect stimuli.
Give 2 examples of receptors.
- Taste receptors on the tongue
2. Sound receptors in the ears
What can receptors form?
Part of larger, complex organs
What do effectors respond to?
To nervous impulses and bring about a change.
How do muscles respond to a nervous impulse?
Muscles contract
How do glands respond to a nervous impulse?
Glands secrete hormones.
What is the CNS?
It is a coordination centre- it receives information from the receptors and then coordinates a response.
What is the response carried out by?
Effectors
Describe the transmission of information to and from the CNS.
Stimulus→ Receptors→ CNS (coordinator)→ Motor neurone→ Effector→ Response
How is information carried from the receptors to the CNS?
By sensory neurones
How are electrical impulses carried from sensory neurones to motor neurones?
By relay neurones
How are electrical impulses carried from the CNS to effectors?
By motor neurones
Where are relay neurones found?
In the central nervous system.
What are relay neurones?
The neurones that carry electrical impulses from sensory neurones to motor neurones.
What is a synapse?
It is the connection between two neurones.
What is the nerve signal transferred by?
By chemicals which diffuse across the gap.
What do the chemicals transferred do in synapse?
These chemicals then set off a new electrical signal in the next neurone.
What are reflexes?
They are rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain.
What do reflexes reduce?
The chances of being injured.
What is a reflex arc?
It is the passage of information in a reflex (from receptor to effector).
What do the neurones in reflex arcs go through?
The spinal cord or through an unconscious part of the brain.
Why are reflexes quicker than normal responses?
You don’t have to think about the response (which takes time).
Why does the body have to balance the amount of energy gained and lost?
To keep the core body temperature constant.
What does the thermoregulatory centre in the brain contain?
Receptors that are sensitive to the temperature of the blood flowing through the brain.
How does the thermoregulatory centre receive information about skin temp.?
It receives impulses from temperature receptors in the skin giving information about skin temperature.
What does the thermoregulatory centre do if the temperature is too hot? (1)
Temperature receptors detect that core body temperature is too high.
What does the thermoregulatory centre do if the temperature is too hot? (2)
The thermoregulatory centre acts as a coordination centre- it receives information from the temperature receptors and triggers the effectors automatically.
What does the thermoregulatory centre do if the temperature is too hot? (3)
Effectors, e.g. sweat glands, produce a response and counteract the change.
What does the thermoregulatory centre do if the temperature is too cold? (1)
Temperature receptors detect that core body temperature is too low.
What does the thermoregulatory centre do if the temperature is too cold? (2)
The thermoregulatory centre acts as a coordination centre- it receives information from the temperature receptors and triggers the effectors automatically.
What does the thermoregulatory centre do if the temperature is too cold? (3)
Effectors, e.g. muscles, produce a response and counteract the change.
What does the thermoregulatory centre do if the temperature is too cold? (4)
Body warms up.
What does the thermoregulatory centre do if the temperature is too hot? (4)
Body cools down.
How do some effectors work?
Antagonistically- they’ll work at the same time to achieve a very precise temperature.
What does working antagonistically allow?
This mechanism allows a more sensitive response.
What does the body do if the temperature is too hot?
- Hair erector muscle relaxed
- Blood supply to surface of skin
- Sweat gland produces sweat
How does producing sweat help with cooling down body temperature?
It evaporates from the skin. This transfers energy to the environment.
How does blood supply to surface of skin help reduce the body temperature?
The blood vessels supplying the skin dilate so more blood flows close to the surface of the skin. This is called vasodilation. This helps transfer energy from the skin to the environment.
What does the body do if the temperature is too cold?
- Hairs erect
- No sweat
- Blood supply shut off
How does the hairs standing up help cool the body temperature?
Hairs stand up to trap an insulating layer of air.
What is vasoconstriction?
It is when blood vessels supplying skin capillaries constrict to close off the skin’s blood supply.
Why does the body shiver when it’s cold?
This needs respiration, which transfers some energy to warm the body.
Give the optimum temperature for enzymes in the body.
Around 37°C
What hormone does your body produce if it is in shock?
Adrenaline
What are hormones?
They are chemical molecules released directly into the blood. They are carried in the blood to other parts of the body, but only affect particular cells in particular organs (called target organs).
When do hormones need to control things in organs and cells?
Hormones control things in organs and cells that need constant adjustment.
What do hormones tend to do?
Relatively long-lasting effects.
What are endocrine glands?
Hormones are produced in (and secreted by) various glands, called endocrine glands.
What makes up your endocrine system?
Endocrine glands
Give 6 examples of glands.
- Pituitary glands
- Ovaries
- Testes
- Thyroid
- Adrenal gland
- Pancreas
What does the pituitary gland produce?
Many hormones that regulate body conditions.
Why is the pituitary gland sometimes called the master gland?
These hormones act on other glands, directing them to release hormones that bring about change.
What are ovaries- females only?
They produce oestrogen, which is involved in the menstrual cycle.
What are testes- males only?
They produce testosterone, which controls puberty and sperm production in males.
What is a thyroid gland?
These produce thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature.
What is the adrenal gland?
These produce adrenaline, which is used to prepare the body for a ‘fight or flight’ response.
What is the pancreas?
This produces insulin, which is used to regulate the blood glucose level.
Give 3 things which makes nerves different from hormones.
Nerves:
- Very fast action
- Act for a very short time
- Act on a very precise area
Give 3 things which makes hormones different from nerves.
Hormones:
- Slower action
- Act for a long time
- Act in a more general way
How can you tell if a response is a nervous response?
If the response is really quick.
How can you tell if a response is a hormonal response?
If a response lasts for a long time.
What does eating food containing carbohydrates do?
Puts glucose into the blood from the gut.
What does the normal metabolism of cells do?
Removes glucose from the blood.
What does vigorous exercise do?
Removes much more glucose from the blood.
Where can excess glucose be stored as?
Glycogen in the liver and in the muscles.
What is the changes in glucose monitored and controlled by?
The pancreas, using the hormones insulin and glucagon, in a negative feedback cycle.
What is insulin?
It is a hormone produced by the pancreas. It decreases the blood glucose level when it gets too high.
What does the body do if the blood glucose level is too high? (1)
The rise in blood glucose is detected by the pancreas.
What does the body do if the blood glucose level is too high? (2)
The pancreas responds by producing insulin, which is secreted into the blood.
What does the body do if the blood glucose level is too high? (3)
Insulin causes body cells to take up more glucose from the blood. Cells in the liver and muscles can take up glucose and convert it into a storage molecule called glycogen.
What does the body do if the blood glucose level is too high? (4)
This causes the blood glucose level to fall.
What is glucagon?
It is a hormone produced by the pancreas. It increases the blood glucose level when it gets too low.
What does the body do if the blood glucose level is too low? (1)
The fall in blood glucose level is detected by the pancreas.
What does the body do if the blood glucose level is too low? (2)
The pancreas responds by producing glucagon, which is secreted into the blood.
What does the body do if the blood glucose level is too low? (3)
Glucose can be stored in the muscles and liver as glycogen. Glucagon causes the glycogen to be converted back into glucose, which enters the blood.
What does the body do if the blood glucose level is too low? (4)
This causes the blood glucose level to rise.
What is diabetes?
It is a condition that affects your ability to control your blood sugar level.
Give 2 types of diabetes.
- Type 1 diabetes
2. Type 2 diabtes
What is type 1 diabetes?
It is where the pancreas produces little or no insulin. This means a person’s blood glucose level can rise to a level that can kill them.
What do people with type 1 diabetes need?
Insulin therapy
What does insulin therapy involve?
Several injections of insulin throughout the day, most likely at mealtimes.
What does the insulin injected do?
It makes sure that glucose is removed from the blood quickly once the food has been digested, stopping the level getting too high.
What does the amount of insulin needed to be injected depend on?
The person’s diet and how active they are.
What do people with type 1 diabetes need to do?
- Limiting the intake of food rich in carbohydrates, e.g. sugars
- Taking regular exercise
What is type 2 diabetes?
It is where a person becomes resistant to their own insulin. This can cause a person’s blood sugar level to rise to a dangerous level.
What can cause type 2 diabetes?
Being overweight can increase your chance of developing type 2 diabetes.
How can type 2 diabetes be controlled by?
By eating a carbohydrate- controlled diet and getting regular exercise.
How does the kidneys make urine?
By taking waste products out of your blood.
What is filtration?
Substances are filtered out of the blood as it passes through the kidneys. This process is called filtration.
What is selective absorption?
Useful substances like glucose, some ions and the right amount of water are then absorbed back into the blood. This process is called selective absorption.
Give 3 substances which can be removed from the body in urine.
- Urea
- Ions
- Water
What are can you not do with the proteins in the body?
Proteins (and the amino acids that they are broken down into) can’t be stored by the body.
What does the body do with the excess amino acids?
They are converted into fats and carbohydrates, which can be stored. This occurs in the liver and involves a process called deamination.
What is the waste product of deamination?
Ammonia
What is Ammonia?
It is toxic so it’s converted to urea in the liver.
What happens to the urea?
It is then transported to the kidneys, where it’s filtered out of the blood and excreted from the body in urine.
What does the body do with ions?
Ions such as sodium are taken into the body in food, and then absorbed into the blood.
What happens if the ion (or water) content of the body is wrong?
This could upset the balance between ions and water, meaning too much or too little water is drawn into cells by osmosis.
What damage does having the wrong amount of water do to your cells?
It can damage cells or mean they don’t work as normal.
How are some ions lost?
Some ions are lost in sweat. This amount is not regulated.
What maintains the right balance of ions in the body?
Kidneys
What does the body do with the right amount of ions?
It is reabsorbed into the blood after filtration and the rest is removed from the body in urine.
What does the body have to do with the water?
Constantly balance the water coming in against the water going out.
Give 2 ways we lose water.
- From the skin in sweat
2. From the lungs when breathing out
How is the amount of water balanced?
It is balanced by the amount we consume and the amount removed by the kidneys in urine.
What hormone controls the concentration of urine?
Anti-diuretic hormone (ADH)
Where and how is ADH released?
It is released into the bloodstream by the pituitary gland.
What does the brain monitor?
The water content of the blood and instructs the pituitary gland to release ADH inti the blood according to how much is needed.
What is the whole process of water content regulation controlled by?
Negative feedback
What happens if your kidneys don’t work properly?
Waste substances build up in the blood and you lose your ability to control the levels of ions and water in your blood.
How can people with kidney failure be kept alive?
By having dialysis treatment- where machines do the job of the kidneys or they can have a kidney transplant.
Why does dialysis have to be done regularly?
To keep the concentrations of dissolved substances in the blood at normal levels, and to remove waste substances.
How does the person’s blood flow in a dialysis machine?
Between partially permeable membranes, surrounded by dialysis fluid. It’s permeable to things like ions and waste substances, but not big molecules like proteins.
What does the dialysis fluid have?
The same concentration of dissolved ions and glucose as healthy blood. This means that useful dissolved ions and glucose won’t be lost from the blood during dialysis.
What can only diffuse across the barrier in a dialysis machine?
Only waste substances (such as urea) and excess ions and water
How many times do patients with kidney failure have to take a dialysis session?
3 times a week
How long does each dialysis session take?
3-4 hours
What does dialysis may cause?
Blood clots or infections
Give 2 disadvantages of a dialysis machine.
- It is not a pleasant experience
2. Expensive for the NHS to run
Give an advantage of dialysis?
It can buy a patient with kidney failure valuable time until a donor organ is found.
What is the only cure to kidney failure?
Kidney transplant
How are healthy kidneys usually transplanted?
From people who have died suddenly.
What does the person must have in order for people to have permission to take the person’s kidneys?
The person who died has to be on the organ donor register or carry a donor card.
Give another way a kidney can be transplanted.
Kidneys can also be transplanted from people who are still alive but there is a small risk to the person donating the kidney.
What can happen if a kidney is transplanted to the patient?
There is a risk that the donor kidney can be rejected by the patient’s immune system.
What is the patient treated with in order for the kidney not to be rejected?
Drugs to prevent this but it can still happen.
Give 2 advantages transplants have over dialysis.
- They are cheaper than dialysis
2. They can put an end to the hours patients have to spend on dialysis
Give a disadvantage of transplant.
There are long waiting lists for kidneys.
Describe adrenaline.
It is a hormone released by the adrenal glands, which are just above the kidneys.
When is adrenaline released?
It is released in response to stressful or scary situations.
How is adrenaline released?
Your brain detects fear or stress and sends nervous impulses to the adrenal glands, which respond by secreting adrenaline.
How does you body get ready for ‘fight or flight’?
By triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles.
Give an example of what your body does for ‘fight or flight’
Adrenaline increases heart rate
What can negative feedback systems be used for?
Your body can control the level of hormones (and other substances) in the blood using negative feedback systems.
What is thyroxine made from?
Iodine and amino acids
Describe thyroxine.
It is a hormone released by the thyroid gland, which is in the neck.
What is the role of thyroxine?
It regulates the basal metabolic rate- the speed at which chemical reactions in the body occur while the body is at rest.
Give another role of thyroxine.
It is important for processes in the body, such as stimulating protein synthesis for growth and development.
What is thyroxine released in response to?
Thyroid stimulating hormone (TSH), which is released from the pituitary gland.
What does the negative feedback system do if the thyroxine level in the blood is higher than normal?
The secretion of TSH from the pituitary gland is inhibited. This reduces the amount of thyroxine released from the thyroid gland, so the level in the blood falls back towards normal.
What is the role of the negative feedback system for thyroxine?
It keeps the amount of thyroxine in the blood at the right level.
What is auxin?
It is a plant hormone that controls growth near the tips of shoots and roots.
What does auxin control?
The growth of a plant in response to light (phototropism) and gravity (gravitropism or geotropism).
How does the plant stimulate cell elongation process?
Auxin is produced in the tips and moves backwards to stimulate the cell elongation process.
Where does the cell elongation process occur?
In the cells just behind the tips.
What happens if the tip of a shoot is removed?
No auxin is available and the shoot may stop growing.
What does extra auxin promote?
It promotes growth in the shoot but inhibits growth in the root.
What happens when a shoot tip is exposed to light?
More auxin accumulates on the side that’s in the shade than the side that’s in the light.
What happens to the cells on the shoot tip when it is exposed to light?
It makes the cells elongate faster on the shaded side, so the shoot bends towards the light.
What happens when a shoot is growing sideways?
Gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side.
What does the uneven distribution of the tip cause?
It causes the lower side to grow faster, bending the shoot upwards.
What will happen to a root growing sideways?
It will also have more auxin on its lower side.
What does the extra auxin do to a root?
It inhibits growth. This means the cells on top elongate faster, and the root bends downwards.
What are auxins useful for?
Controlling plant growth.
Give 3 uses of auxin.
- Killing weeds
- Growing from cuttings with rooting powder
- Growing cells in tissue culture
What does it mean if something is broad-leaved?
Most weeds growing in fields of crops or in a lawn are broad-leaved.
What type of leaves are grasses and cereals?
They have a very narrow leaves.
How have selective weedkillers been developed?
Using auxins
What do selective weedkiller affect?
They only affect the broad-leaved plants.
What do selective weedkillers do?
They totally disrupt their normal growth patterns, which soon kills them, whilst leaving the grass and crops untouched.
What is cutting?
A cutting is part of a plant that has been cut off it, like the end of a branch with a few leaves on it.
What happens if you stick cuttings in the soil and add rooting powder containing auxin to it?
They will produce roots rapidly and start growing as new plants.
Give an advantage of adding rooting powder to cuttings?
It enables growers to produce lots of clones of a really good plant very quickly.
What can tissue culture be used for?
To grow clones of a plant from a few of its cells.
How is tissue culture performed?
Hormones such as auxins need to be added to the growth medium (along with nutrients) to stimulate the cells to divide to form both roots and shoots.
What is gibberellin?
It is a plant hormone which stimulates seed germination, stem growth and flowering.
Give 3 uses of gibberellin.
- Controlling dormancy
- Inducing flowering
- Growing larger fruit
What is dormancy?
Lots of seeds won’t germinate until they’ve been through certain conditions. This is called dormancy.
What happens to seeds that have been treated with gibberellin? (1)
It alters dormancy and make them germinate at times of year that they wouldn’t normally.
What happens to seeds that have been treated with gibberellin? (2)
It also helps to make sure all the seeds in a batch germinate at the same time.
Give 2 examples of the certain conditions plants require to flower.
- Longer days
2. Low temperatures
What happens to plants that are treated with gibberellin? (1)
They will flower without any change in their environment.
What happens to plants that are treated with gibberellin? (2)
It can also be used to grow bigger flowers.
Describe seedless varieties of fruit.
They often do not grow as large as seeded fruit.
What happens to seedless varieties of fruit when added with gibberellin?
They will grow larger to match the normal types.
What is ethene?
It is a gas produced by aging parts of a plant.
What does ethene do?
It influences the growth of the plant by controlling cell division. It also stimulates enzymes that cause fruit to open.
Give another use of what ethene can do?
It can be used to speed up ripening of fruits- either while they are still on the plant, or during transport to the shops.
How can ripening be delayed while the fruit is in storage?
By adding chemicals that block ethene’s effect on the fruit or reduce the amount of ethene that the fruit can produce.
How can ethene be removed from the air?
By using chemicals that can be used to react with ethene to remove it from the air.
Give an advantage of picked up fruits which are still unripe?
They are firmer and less easily damaged.
How is the fruits made ‘perfect’ as soon as it is in shops?
Gas is added to the fruits on the way to the supermarket.
