Comprehensive revision for B1 AQA GCSE Biology

Very full notes I used to revise from for Unit B1-A and B for GCSE Biology AQA

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B1a: Human Biology
B1a: 1 Coordination and Control
-Hormones are chemicals that help control and coordinate many of the processes in your body
-They are made by special glands and then secreted into the bloodstream to be carried to their
target organs in the body
-They can act very quickly but often have slow, long lasting effects
The Nervous system
-Your body is very sensitive to changes in the world around you
-Cells called receptors detect any of these stimuli and the nervous system will then use an electrical
impulse to enable you produce a reaction
-Receptors are usually found in sense organs, e.g. eyes/skin
How your nervous system works
Electrical impulse travels along sensory neurone Impulses are sent along the motor neurones
-Neurones are usually found in bundles of hundreds/thousands known as nerves
-The Central Nervous system is made up of the spinal cord and brain
-Effector organs are muscles/glands. Muscle responding by contacting and glands respond by
releasing chemical substances
Reflex actions
-These are automatic responses which happen without giving you time to think because they are so
fast e.g. pulling your hand away from a hot pan
- They are very important as they help you avoid danger or harm as they happen so fast. There are
aso reflex es that take care of basic bodily functions e.g. breathing
How do reflexes work?
Reflex actions involve tree types of neurone: semsory neurnes
motor neurones, and
relay neurones, found in the spinal cord
How reflexes work
Electrical impulse travels along sensory neurone
Impulses are sent along the motor neurone

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How a synapse works
-A synapse is a junction between two nerve endings.
-When an electrical impulse arrive at the junction bwteween two neurones, chemicals are released
which cross the synapse and arrive at receptor sites n the next neurone.…read more

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Pros Cons
The pills have helped reduce family sizes in the The pill can cause health problems/side effects
developed world =less poverty as not so much such as headaches and weight gain but even
money needing to be spent on food etc things as extreme as strokes and heat attacks
and poses a health risk for the mother-multiple
It is also used in a few countries of the Using the pill raises many ethical issues for
developing world e.g.…read more

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The metabolic rate
-The metabolic rate is the rate at which chemical reactions take place in the cells of the body
-The metabolic rate varies from person to person, meaning they will need different amounts of
energy in their diets
-The proportion of muscle to fat in your body affects your metabolic rate and therefore men have a
higher metabolic rate than women do
-Metabolic rate is affected by the amount of exercise you do (increases) and also factors in your
Weight problems
-Scientists…read more

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These foods contain high proportions of fat and/or salt which have a real impact on your health, and
make you overweight
-Cholesterol is as substance made in the liver and found in the blood
-It is needed to make hormones/cell membranes deal with stress
-The amount/type of fat you eat affects the level and type of cholesterol in your blood
-High cholesterol levels are linked to heart disease as cholesterol builds up in your arteries and
blocks them
Controlling cholesterol
-The amount of cholesterol…read more

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Why use drugs?
-To help them cope with everyday life
Excitement/escape from life or group pressure
Drug Abuse
-People take drugs for a reason often to make them feel good about themselves/peer pressure if
they are young
-Many recreational drugs are addictive and do serious harm to your health
-Hard drugs lead to sever health problems.…read more

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Alcohol and society
Alcohol not only puts yourself at risk but affects those around you as well, as alcoholics can become
very violent and do things they regret doing later
Drink driving is very common, particularly in youths, and this is a cause of many road accidents
involving youths.…read more

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Lung Cancer and Smoking
-Timeline of Evidence building up against smoking
1908: Sale of cigarettes to children under sixteen banned
1912-The first suggestion of a link between lung cancer and smoking
1914-18 Smoking increased dramatically due to soldiers smoking in the War
1930s-Britain has highest smoking rate
1951-Link found between the number of men who smoked and who had lung cancer
1953-Mice who had tar painted on their backs developed cancer
1960s-Cigarette consumption fell due to dangers being published in a report
1997-Smoking seen to…read more

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Average size -1m
-Colonies can be seen with naked eye
-Single celled organism made up of cytoplasm surrounded by cell wall and membrane-NO NUCLEUS
so DNA free in cytoplasm
-Binary fission to reproduce
-Produce toxins that cause symptoms of disease
3 types-cocci, spiral and rods
-Some useful: In foods e.g.…read more

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Hairs-sebum produced-antiseptic to kill microbes
-Eyes-tear glands produce tears containing antiseptic that kills microbes and blinking spreads this
around the eye
-Stomach-HCL produced which destroys microorganisms taken in through mouth
-Skin-water-proof barrier preventing microorganisms reaching the vulnerable tissues underneath
Immune Response
-White blood cells-Phagocytes--Engulf and destroy pathogens
-Attracted to chemicals released from bacterium and surrounds
Bacterium, putting it in a vesicle
-Enzymes in vesicle break down pathogen
Lymphocytes- Produce antibodies that act against pathogens by targeting
particular bacteria and destroying them, and which can be…read more


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