The Nitrogen Cycle

The Nitrogen Cycle:

Nitrogen is used to make proteins and other substances for organisms as they grow. Plants and animals get nitrogen from nitrogen-containing substances. Plant roots absorb nitrogen compounds from the soil and use them to make nitrogen compounds in their biomass.

Animals get nitrogen compounds in their food. Most of which are sued to make nitrogen compounds in new biomass but some are lost in faeces and urine.

Plants would die out if there wasn't a way to convert nitrogen compounds back to nitrates in the soil.. So when decomposers feed on waste they break down some proteins and urea (a nitrogen rich substance in urine) to ammonia and release it in the soil.

The soil contains nitrogen-fixing bacteria that fixes nitrogen gas into ammonia.

In legume roots  mutualistic nitrogen-fixing bacteria is found. This bacteria lives inside root nodules and provide plants directly with ammonia.

Plants grow better with nitrates. So some nitrifying bacteria in soil converts ammonia to nitrates.

If soil starts lacking in oxygen the dentrifying bacteria will convert nitrates back to nitrates and others convert nitrates back to nitrogen gas.

Lightning can occasionally provide energy to combine oxygen and nitrogen gases in the air that quickly form nitrates.

Key Words:

Urea

Nitrogen-fixing bacteria

Root nodules

Nitrifying bacteria

Denitrifying bacteria

Questions:

1. Why are decomposers important in the nitrogen cycle?

2. Why does adding manure to soil increase the nitrate content?

What you should know:

An understanding of how nitrogen is recycled:

a. nitrogen gas in the air cannot be used directly by plants and animals.

b. nitrogen-fixing bacteria living in root nodules or the soil can fix nitrogen gas

c. the action of lightning can convert nitrogen gas into nitrates

d. decomposers break down dead animals and plants

e. soil bacteria convert proteins and urea into ammonia

f. nitrifying bacteria convert this ammonia to nitrates

g. plants absorb nitrates from the soil

h. nitrates are needed by plants to make proteins for growth

i. nitrogen compounds pass along a food chain or web

j. denitrifying bacteria covert nitrates to nitrogen gas

The Carbon Cycle

The Carbon Cycle:

Carbon atoms that are part of a carbon dioxide molecule in the atmosphere could diffuse into a leaf. During photosynthesis the carbon atom will become part of glucose.

If glucose is used by a plant for respiration the carbon atom will become part of carbon dioxide and release back in the atmosphere. But it could be changed into other carbon compounds and used to make plant biomass.

Carbs, fats and protein in plants all contain carbon atoms so when a animals eats it some are broken down and taken to the body while others come out a s faeces.

If plants and animals aren't eaten and just die, like decomposer organisms such as fungi, they start the process of decay. They feed on animal waste and break down carbon-containing compounds using some for respiration and some to build more complex compounds in their body.

If many dead plants are buried to quickly so decomposer organisms can't feed on them, they may be changed by heat and pressure into coal. Oil and natural gas are also formed dead sea plants or animals aren't decomposed.

They're all fossil fuels which contain carbon compounds. 

Combustion is a chemical reaction when substances burn, combining with oxygen to produce heat and waste products such as carbon dioxide.

The Carbon cycle is the movement of carbon through dead and living organisms and the atmosphere. 

Key Words:

Faeces
Decomposer
Decay
Fossil fuels
Combustion
Carbon cycle

Questions:

1. What process removes carbon dioxide from the air?
2. Which process releases carbon dioxide in the air?


What you should Know:

An understanding of how carbon is recycled:
a. during photosynthesis plants remove carbon dioxide from the atmosphere
b. carbon compounds pass along a food chain
c. during respiration organisms release carbon dioxide into the atmosphere.
d. decomposers release carbon dioxide into the the atmosphere.
e. combustion of fossil fuels releases carbon dioxide into the atmosphere.

Pollution Indicators

Pollution Indicators:

The more pollution caused the more harm there is to habitats.Indicator species are organisms that are so sensitive to polluting chemicals that we use them to help show us the presence of pollution. E.g. Blackspot fungus are when roses are infected and killed by sulfur dioxide in the air.

Lichens are mutualistic relationship between a fungus and alga, different species of lichens are affected differently by air pollution, so they can be used as pollution indicators.

Different animals that live in water need different amounts of oxygen. E.g. Stonefly larvae and freshwater shrimps need lots of oxygen whereas bloodworms and sludgeworms need little.

The UK produces a lot of waste which ends up being buried in landfill sites. There is a risk of pollution which means materials can't be used again. We're in danger of running out of some raw material.

Recycling is taking materials out of waste and converting them into new products that we can use:

• Metals can be melted down and recycled as new drinks cans or part of a car
• Paper can be recycled as more paper or cardboard
• Plastic bottles can be recycled as fleece clothing.

Key Words:

Indicator species
Blackspot fungus
Lichens
Stonefly larvae 
Freshwater shrimps
Bloodworms
Sludgeworms
Recycling

Questions:

1. What is indicator species?
2. Why is clean air not good for rose growers?
3. Why do animals need oxygen?
4. What are the advantages of recycling?

What you should Know:

An understanding of how scientists can use the presence or absence of indicator species as evidence to assess the level of pollution:
a. polluted water indicator - bloodworn, sludgeworm
b. Clean water indicator - stonefly, freshwater shrimps
c.air quality indicator - lichen species, blackspot fungus on roses

An understanding of how recycling can reduce the demand for resources and the problem of waste disposal, including paper, plastics and metals.

Pollutants and Plant Growth

Pollutants and Plant Growth:

Gas clouds in volcanoes contain  a lot of sulfur dioxide which can cause damage. Sulfur dioxide dissolves in water vapour in the air and makes a very strong acid.

Sulfur dioxide can also be produced by power stations. It dissolves in water vapour in clouds and forms sulfuric acid which falls as acid rain. Acid rain destroys trees and can make lakes too acidic for organisms to live in.


What you should Know:

The effects of pollutants on plant germination and growth.

Pollution

Pollution:

Population growth is an increase in population over time. There is increases in food production, medicines and better living conditions which means more babies survive to have young of their own.

As the human population increases we need more water and more food. Crops often grow better with fertiliser added to soil. 

Everything that we use every day requires resources, this includes fossil fuels to generate electricity to make them.

If we aren't careful about making resources we risk releasing pollutants and damaging organisms. Sulfur dioxide gas is released when fossil fuels are burnt. It pollutes the air if concentration is too high.

Eutrophication is the addition of chemicals to water, nitrates and phosphates, which encourage plant growth.

As nutrient concentration increases organisms in the water are affected. This leads to decrease in oxygen concentration and death of many animals.

Key Words:

Population growth

Fertiliser

Pollutants

Eutrophication

Questions:

1. Why is there an increase in population?

2. Why is fertiliser use increasing?

3. How is eutrophication caused?

4. How can it damage the environment?

What you should Know:

How to analyse interpret and evaluate data on global population change.

How the increase in human population contributes to an increase in th eproduction of pollutants, including phosphates, nitrates and sulfur dioxide.

How eutrophication occurs and the problems associated in a aquatic environment.

Parasites and Mutualists

Parasites and Mutualists:

In most feeding relationships the predator kills and eats it's prey. Parasitism is a feeding relationship in which two organisms live together in which one is feeding off the other. The organisms that feeds is called a parasite and the organisms it feeds on is the host.

Some parasites live outside a host's body e.g. Headlice. Others live inside. The tapeworm live in the intestines of vertebrates. Tapeworms eggs live the host's body through it's faeces. Their eggs are then swallowed by other animals and tapeworms grow inside them.

Parasites harm their hosts. Tapeworms take nutrients from the host's gut. This can cause the host to lose weight.

European mistletoe is a parasite plant. It's leaves photosynthesis but its roots grow into the veins of a host tree and absorb its mineral salts.

Mutualism is when two organisms live together but both organisms benefit. One such pair are oxpeckers and large herbivores in Africa. Oxpeckers eat parasitic insects that live on the herbivore . The herbivore carrier around the oxpecker on its head.

Another such example is when cleaner fish eat parasites from the skin of larger fish while the larger fish carry them around.

Some organisms live in mutualistic relationships inside other organisms. Nitrogen-fixing bacteria is a bacteria that can turn nitrogen in the air into nitrogen compounds. Some live in the roots of legumes (plants that produce pods). The bacteria gains chemical substances from the plant which they use as food. The plant gains nitrogen compounds so it can grow well.

Chemosynthetic bacteria are producers who get their energy from chemical substances rather then light. Some live inside tubeworms. Tubeworms get chemicals the bacteria needs and tubeworms feed on substances made by bacteria.


Key Words:

Prey 
Predator
Parasitism
Parasite
Host
Mutualism
Cleaner fish
Nitrogen-fixing bacteria
Legumes
Chemosynthetic bacteria


Questions:

1. How do headlice benefit from parasitism
2. How can a tapeworm kill its host?
3. How do both the oxpecker and herbivore benefit from mutualistic relationship?
4. What is the difference between parasitic and mutualistic relationships?


What you should Know:

How the survival of some organisms may depend on the presence of another species:
a. Parasitism including:
i. fleas
ii. head lice
iii. tapeworms
iv. mistletoe
b. Mutualism including:
i. oxpeckers
ii. cleaner fish
iii. nitrogen-fixing bacteria in legumes
iv. Chemosynthtic bacteria in tube worms in deep-sea vents.

Interdependence and Food webs

Interdependence and Food Webs:

All organisms need food. Some are producers whom make their own food. Others get their food from other organisms. Primary consumers eat plants and secondary consumers eat primary consumers.

Food chains show what organisms eat what. The organisms that feed at the same level in a food chain are at the same trophic level. Food chains can be joined together to create a food web. This shows the feeding relationships between different organisms. Interdependent organisms depend on each other for food. 

Energy stored in food is released during respiration. Some energy is transferred into biomass. Biomass is substances that form tissues. Energy in biomass is transferred to the next organisms in a food chain when it's eaten.

But some energy that's released in respiration is transferred into forms of energy that aren't useful. So this energy is wasted.

If we measured the biomass of all the organisms in a food chain we could draw a pyramid of biomass.
Here is an example:

Key Words:

Producers
Primary consumers
Secondary consumers
Food chains
Trophic level
Food web
feeding relationships
Interdependent
Respiration
Biomass
Pyramid of biomass


Questions:

1. What is a producer?
2. Why do food chains start with a producer?
3. What happens to the biomass in a food chain as you go up the trophic levels?
4. How are living things interdependent?

What you should Know:

That interdependence is they dynamic relationship between all living things.

An understanding of how some energy is transferred to less useful forms at each trophic level and this limits the length of a food chain.

An understanding that the shape of a pyramid of biomass is determined by energy transferred at each trophic level

Antiseptics: PCA:

Antiseptics: PCA:

As we know that microorganisms cause infectious diseases, we've found ways of killing microorganisms to prevent the spread and to cure people.

Joseph Lister was a Scottish surgeon who first showed antiseptics could stop infections.

What you should Know:

The effects of antiseptics or antibiotics on microbial cultures.

Antiseptics and Antibiotics

Antiseptics and Antibiotics:

Animals, including humans, have many ways to protect themselves from  pathogens. Some of these are physical barriers that stop pathogens getting into the body. We also have chemical defences that help kill pathogens before they can harm us.

Antiseptics is a substance used to stop the spread of pathogens and kill microorganisms outside of the body. They're important where there are a lot of pathogens such as a toilet.

Antibacterial is an antibiotic that kills or slows the growth of bacteria. Plants defend themselves with this. Humans also use this. They put witch Hazel in aftershave to help prevent infections through cuts in the skin.

Antibiotics are substances that kill or slow the growth of bacteria and some fungi. Antibiotics that only affect fungi are called antifungals. Antibiotics can not kill viruses.

Bacteria in a population show variation so some will be more resistant to an antibiotic and take longer to be killed then others.

Less resistant bacteria is killed first. However more resistant bacteria still stays and can cause infection again if the person stops taking antibiotics.

MRSA is a bacterium resistant to many antibiotics.

Key Words:

Physical Barriers

Chemical Defences

Antiseptics

Antibacterials

Antibiotics

Antifungals

Variation

Resistant

MRSA

Questions:

1. Why wiping a surface where meat is being prepared with antiseptics helpful?

2. Why should you always finish a course of antibiotics even if you're feeling better?

What you should know:

How the human body can be effective against attacks from pathogens, including:

a. physical barriers - skin, cillia, mucus.

b. chemical defence - hydrochloric acid in the stomach, lysozymes in tears.

An understanding that plants produce chemicals that have antibacterial effects in order to defend themselves, some of which are used by humans.

How antiseptics can be used to prevent the spread of infection.

The use of antibiotics to control infection, including:

a. antibacterials to treat bacterial infection

b. antifungals to treat fungal infection

How to evaluate evidence that resistant strains of bacteria, including MRSA, can arise from the misuse of antibiotics.

Pathogens and Infection

Pathogens and Infection:

A pathogen is a microorganism that causes infectious diseases when they're passed to an infected person to an infected person.

Bacteria Pathogens are:

• Cholera
• Food poisoning
• Dysentery
• Tuberculosis 

Virus Pathogens are:

• Influenza
• Mumps
• Measles
• AIDS

Fungi Pathogens are:

• Athletes Foot Fungus

Protoctists Pathogens are:

• Protozoan that causes Malaria

Pathogens can be spread by direct contact or carried by vectors. Vectors are animals that pass pathogens from one person to another.

Key Words:

Pathogens
Infectious diseases
Bacteria
Viruses
Fungi
Protoctists
Protozoan
Vectors

Questions:

1. What is a pathogen?
2. Draw and complete a table showing pathogens and examples of diseases they spread.
3. Give two vector examples.

What you Should Know:

That infectious diseases are caused by pathogens.

How pathogens are spread, including:
a. In water, including cholera bacterium
b. by food, including Salmonella bacterium
c. airborne, including influenza virus.
d. by contact, including athlete's foot fungus.
e. by body fluids, including HIV
f. by animal vectors, including:
  i. housefly: dysentery bacterium
 ii. Anopheles mosquito: Malarial protozoan.

Ethics and Transplants

Ethics and Transplants:

A transplant is taking an organ from one person (a donor) and put into another person to replace an organ that no longer functions properly. 

There aren't enough donor organs so 1000's of people die. Doctors must decide who has first priority.
They follow a scientific criteria. It included whether the patient and donor:

• Have similar tissues - the closer the match the more likely the transplant is to be successful.
• Are similar ages - a child's organ wouldn't be successful in an adult.
• Are geographically close - the quicker it's transplanted it's more likely to be successful.
• How ill the patient is - a very ill patient is less likely to survive then a healthier one.

Some hospitals don't give liver transplants to patients who abuse alcohol unless they stay off alcohol for six months outside of hospital.

Being clinically obese can damage the heart. Some hospitals won't perform heart transplants on them unless they stick to a weight loss diet.

An ethical decision use ethical criteria to reach an answer that most people think is right/fair. Sometimes they're hard to make as different people have different standards by which they judge what is right or wrong.


Key Words:

Transplant
Donor
Criteria
Clinically obese
Ethical Decision 

Questions:

1. Why must doctors choose who gets a transplant?
2. How might ethical decisions for liver transplants differ from hospital to hospital?
3. How do you think health services should decide who gets organ transplants?

What you Should Know:

The ethics of organ transplants, including:
a. Liver transplants for alcoholics
b. Heart transplants for the clinically obese
c. The supply of organs

The effects of Alcohol

The effects of Alcohol:

The short-term effects of Alcohol are:

• Slows down activity in the brain and nervous system
• Affects reaction times making the person take longer to respond
• It can lower inhibitions so drinkers are likely to do things they don't normally do. Including taking dangerous risks.
• Blurred Vision
• Can effect coordination
• Makes it difficult to do simple tasks
• Unconsciousness
• possible death on choking on vomit
• Breathing can stop

Long term effects of Alcohol are:

• Damage all of the organs in the body
• Cirrhosis of the liver so normal tissue is destroyed co liver can't function properly which can cause death
• Damages the brain 
• Effects memory
• Causes blood clots in the brain
• It can become addictive so you can become an alcoholic.

Alcohol can also effect people around us. Alcoholics can be violent towards others if they become drunk. They could be accidents and an alcoholic could commit suicide.


Key Words:

Inhibition
Cirrhosis

Questions:

1. Why shouldn't you drive after drinking Alcohol?
2. List three short term effects of drinking alcohol.
3. List two long term effects of drinking alcohol.
4. Explain why liver is effected by drinking.


What you should Know:

Evidence of some harmful effects of alcohol abuse:
a. in the short term - blurred vision, lowering of inhibitions, slowing of reactions.
b. in the long term - liver cirrhosis, brain damage.

The damage caused by Smoking

The Damage caused by smoking:

Tar is a sticky substance in smoke which contains chemical substances called carcinogens. This can cause cancer mostly in the lungs or mouth.

Carbon monoxide is a poisonous gas that reduces the amount of oxygen that red blood cells can carry. A lack of oxygen can cause leg pains when walking.

Carbon monoxide also cause blood vessels to narrow so body cells get even less oxygen and might even die. Dead tissue can get infected and therefore removed. And if the heart muscles get too less oxygen this can cause a heart attack which may kill.

Nicotine is the addictive part of tobacco smoke. Addiction can start as soon as you've had four cigarettes but can last for years, even after you've given up.

It can take many years for smoking to create enough damage in the body to cause death. During which the person will be exposed to many other substances, which makes it hard to prove that smoking was the cause of the death.


Key Words:

Tar
Carcinogens
Carbon monoxide
Nicotine

Questions:

1. What effects do carbon monoxide have on the body?
2. Why do people find smoking hard to give up?
3. Why is it hard to prove smoking is the cause of a death?


What you should Know:

The effects of some chemicals in cigarette smoke, including:
a. Nicotine as a addictive drug
b. Tar as a carcinogen
c. Carbon monoxide reducing the oxygen-carrying ability of the blood.

How to evaluate data relating ot the correlation between smoking and its negative effects on health.

Reaction times and Drugs: PCA

Reaction times and Drugs: PCA:

Amphetamine is a type of drug used in cold remedies. They help unblock your nose but can also have other effects like making people more alert and decreasing their reaction times. This is the effect that's put it ont eh banned substances for athletes.


Key Words:

Reaction times


What you should know:

What reaction times is.

Effects of Drugs

Effects of Drugs:

Any substance or chemical that changes the way the body works is called a drug. Some drugs can change the way we feel, think and act.

Drugs are grouped depending on what effect they have on us:

Narcotics makes us feel sleepy.

Painkillers block some nerve impulses so we feel less pain. Eg. Morphine.

Hallucinogens change the way the brain works, particularly how we see, feel and hear. E.g. LSD

Stimulants increase the speed of nerve impulses. This speeds up reaction times (the time it takes for the body to respond to an outside stimulus). E.g. Caffeine.

Depressants slow down the activity of neurones in the brain and help us relax. E.g. Alcohol.

A drug used to make people feel a certain way is a recreational drug.

Medicines help to limit damage caused by diseases or injury.

Some drugs are legal but some are only legal to buy at certain ages. Other drugs are illegal because they can have dangerous effects. 

Most drugs are addictive so people become dependent on the drug and feel they can't function without it.

Key Words:

Drug

Narcotic

Painkillers

Hallucinogens

Reaction Times

Depressants

Legal

Illegal

Addictive.

Questions:

1. What is a drug?

2. Find an example of a narcotic.

3. How does alcohol increase reaction times?

What you should know:

What a drug is as a chemical substance, such as narcotic or hallucinogen, that effects the Central Nervous System, causing changes in psychological behaviour and possible addiction.

The general effects of:

a. Painkillers that block nerve impulses, including morphine.

b. Hallucinogens that distort sense perception, including LSD

c. Stimulants that increase the speed of reactions and neurotransmission at the synapse, including caffeine.

d. Depressants that slow down the activity of the brain, including alcohol.

Uses of Plant Hormones

Uses of Plant Hormones:

Selective weedkiller is a weedkiller that contains artificial plant hormones and will kill only certain types of plants. Most selective weedkiller kill plants with broad leaves and not those with narrow leaves.

Rooting powder is a powder that contains plant hormones called auxins that help plant cuttings to grow roots quickly.

Some fruits are sprayed with plant hormones so fruits develop without their seeds causing seedless fruit! Also some fruits are sprayed with gibberellins to increase their size.

Plant hormones are sprayed onto

• Fruit trees so the fruit doesn't fall off and becomes damaged; it also allows the fruit to grow larger.
• Fruit trees speed up ripening . So all the fruit ripens and can be picked up in one go.
• So unripe fruit can become ripe.

Key Words:

Selective Weedkiller
Rooting Powder
Cuttings
Ripening


Questions:

1. Why are weedkillers 'selective'?
2. What's an advantage of using rooting powder?
3. Why's plant hormones sprayed onto fruits?

What you should know:

How to analyse, interpret and evaluate data from plant hormone experiments , including the action of plant hormones and gibberellins.

How to demonstrate an understanding of the uses of plant hormones, including:
a. Selective weedkillers
b. Rooting Powder
c. Seedless fruit
d. Fruit ripening

Plant Hormones

Plant Hormones:

Plants responding to a stimulus by growing towards or away from it is called tropism. Tropism caused by light is called phototropism. A tropism away from a stimulus is negative tropism. Plant roots are negatively phototrophic. Plant shoots are positively phototrophic, to get enough light for photosynthesis.

Plants produce hormones called plant growth substance to respond to stimuli. 

An Auxin causes positive phototropism. They're produced in the tips of shoots and effects the growth and elongation of cells in plants. They cause shoots to grow towards the light.

Auxin's are also found in the tips of roots where they cause cells to stop elongating which causes positive gravitropism (or geotropism) which is growth towards gravity. 

Once a seed germinates roots and shoots start to grow. The seed releases plant hormones called gibberellins. This causes starch in a seed to turn into sugars which the seed uses for energy to grow. It can also stimulate flower and fruits in some plants.

Key Words:

Tropism

Phototropism

Negative tropism

Photosynthesis

Plant growth substances

Auxin

Positive gravitropism

Geotropism

Germinates

Gibberellins

Questions:

1. What effects do auxin's have on cells in shoot tips?

2. What is tropism?

3. In the experiment above explain what's happened to each one

4. What does a gibberellin do?

What you should know:

How plant growth substances bring about:

a. Positive phototropism in shoots.

b. Positive gravitropism in roots.

How auxins bring about shoot curvature using cell elongation.

How to analyse, interpret and evaluate data from plant hormone experiments, including the action of auxins and gibberellins.

Tropic Responses: PCA:

Tropic Responses: PCA:

Plants respond to stimuli. Roots respond to the direction of gravity by growing towards it. Stems and shoots grow towards the light.

Charles Darwin wasn't just interested in Evolution, he also write about plants. He discovered that barley seedlings bent as they grew towards the light.


What you should've learnt:

Investigate tropic responses

Diabetes

Diabetes:
Diabetes is a disease in which a person can not control their blood glucose concentration at the correct level. Low blood glucose concentrations can cause unconsciousness. High blood glucose concentration cause tiredness and can damage organs. If blood glucose concentration is too high, kidneys get rid of it by putting it in urine.

Type 1 diabetes is a diabetes in which the pancreas doesn't produce insulin. So when blood glucose concentrations go too high the body can't bring them back to the correct level. So they must inject insulin each day.

Insulin must be injected into the subcutaneous fat layer because fat easily absorbs insulin. 

Diabetics need to control factors that lower blood glucose levels with those that increase the levels. So the more exercise the less insulin they need to inject.

Type 2 diabetes occurs when cells in a persons body become resistant to insulin even though the hormone is produced. 

Factors that help to cause type 2 diabetes are high-fat diets, lack of exercise, old age and being obese.

Type 2 diabetes is controlled by changing a person's diet and increasing their exercise intake.

People are classed as obese if they have a body mass index (BMI) over 30. 
To calculate a person's BMI you must follow this formula:

BMI = Weight in kilograms
         __________________
            (height in metres)²



Key Words:

Diabetes
Type 1 Diabetes
Subcutaneous Fat
Type 2 Diabetes
Body Mass Index


Questions:

1. What is diabetes?
2. Why must people with type 1 diabetes inject insulin?
3. What must people with type 2 diabetes do to control it?
4. Why does type 2 diabetes not require insulin?


What you should've learnt:

That type 1 diabetes is caused by a lack of insulin.

That Type 1 diabetes can be controlled, including the roles of diet and injection of insulin usually into the subcutaneous fat.

How, in Type 1 diabetes, the level of physical activity and diet affect the amount of insulin required.

That Type 2 diabetes is caused by a person becoming resistant to insulin.

How Type 2 diabetes can be controlled by diet and physical activity.

The correlation between obesity (including calculations of BMI) and Type 2 diabetes.

Hormones

Hormones:

Hormones are produced and released by endocrine glands. Organs that respond to a certain hormone are called target organs.

Carbohydrates in food are mainly digested into glucose. After you've eaten the concentration of glucose in your blood rises. When it goes too high the pancreas releases insulin. This is carried around the body in your blood.

Insulin effects cells that include those in the liver. These take glucose out of the blood and convert it into glycogen. This acts as a glucose store. So levels of glucose in the blood decreases.

If your blood sugar level goes too low your pancreas releases glucagon. This is carried in the blood so the cells in the liver turn glycogen back into glucose. Glucose is then released in the blood.

Key Words:

Hormones
Endocrine Glands
Target Organ
Glucose
Concentration
Pancreas 
Insulin
Glycogen
Glucagon


Questions:

1. What is an endocrine gland?
2. What does glycogen do?
3. Explain the stages involved in the control of rising blood glucose levels by insulin.


What you should've learnt:

That hormones are produced in endocrine glands  and transported by the blood to their target organs

How blood glucose levels are regulated by insulin and excess blood glucose is converted to glycogen in the liver.

How blood glucose levels are regulated by glucagon causing the conversion of glycogen to glucose.

Responding to Stimuli

Responding to Stimuli:

When the brain receives impulses from receptor cells it creates a response. Response impulses are sent to the effectors which carry out an action.

Neurones that receive impulses from receptor cells are Sensory Neurones. They have a long dendron and an axon.
Neurones that take impulses to effectors are Motor Neurones. They have no dendron. Their dendrites are on the cell body.
Relay neurones are short neurones which are found in the spinal cord. This is where they link Motor and Sensory neurones. They also make up the brain.

It's important to remember the following order:
Stimulus
Receptors
Sensory Neurone
Relay Neurone
Motor Neurone
Effectors
Response

Sensory Neurone:

Myelinated Sheath is a fatty layer that surrounds the axon. It insulates neurones from surrounding tissue and allows impulses to be carries faster.

A Synapse is the point at which two neurones meet. There is a tiny gap between neurones at a synapse , which can not transmit an electrical impulse. Impulses are transmitted across the gap by a chemical substance called Neurotransmitters.

When you pick up a hot object you drop it suddenly to stop it burning you, and you don't have to think about it first. This is a reflex. Reflex actions are automatic responses that are very quick and protect the body. They use reflex arcs which are neurone pathways where a sensory neurone directly controls a motor neurone.


Key Words:

Response
Effectors
Sensory Neurones
Motor Neurones
Relay Neurones
Myelinated Sheath
Synapse
Neurotransmitter
Reflexes
Reflex Arcs


Questions:

1. Where are the receptor cells that receive the stimulus?
2. What is the order in which neurones follow?
3. What is a reflex?
4. Why is it useful to have reflexes without having to think?
5. What is a synapse?


What you should've learnt:

The structure and function of Sensory, relay and motor neurones and synapses including: 
a. The role of the myelinated sheath
b. The role of neurotransmitters
c. The reflex arc

Skin Sensitivity: PCA

Skin Sensitivity: PCA:

Your skin can detect many different stimuli, including touch, pressure, pain, heat and cold. For each of these stimuli there is a different sort of receptor cell.

What you should've learnt:

Human responses to external stimuli.