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The units in this module are:

B1a – Fit for life

B1b – What’s for lunch?

B1c – Keeping healthy

B1d – Keeping in touch

B1e – Drugs and you

B1f – Staying in balance

B1g – Gene control

B1h – Who am I?

Click on the links to take to the topic you wish to revise.

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Circulatory system

Blood pressure

Healthy blood pressure

Respiration (aerobic)

Respiration (anaerobic)Main menu

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Circulatory System

The circulatory system consists of the heart and blood vessels.

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The heart pumps blood around the body in vessels called arteries, capillaries and veins.

The heart is a pump.

It alternately relaxes to fill with blood and contracts to squeeze out the blood into the arteries

Blood Pressure

The blood is always under pressure.

Blood pressure is a measure of the force of blood per unit area.

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Blood pressure is at its highest when the heart muscle contracts, forcing blood into the arteries.

This is called the systolic blood pressure.

When the heart relaxes, the pressure in the arteries decreases.

This is called the diastolic blood pressure.

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Healthy Blood Pressure

Normal blood pressure is about 120/80 mmHg

(120 is the systolic and 80 is the diastolic)

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It can be affected by age and lifestyle.

• Regular exercise strengthens the heart

• Healthy diet can also help keep normal blood pressure

The following can lead to high blood pressure:

Excess weight, lack of exercise, poor diet, high stress, smoking, alcohol

Respiration (aerobic)

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Living things need oxygen to function.

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The circulatory system carries oxygen and glucose to all cells so they can release energy through aerobic respiration.

glucose + oxygen carbon dioxide + water + energy

C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy

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Respiration (anaerobic)

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Anaerobic respiration takes place without oxygen.

It releases a small amount of energy quickly through the incomplete breakdown of glucose.

Glucose Lactic acid

The lactic acid produced is relatively toxic to the cells and can cause cramp and muscle fatigue

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A balanced diet

Body mass index

Deficiencies

Eating disorders

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A Balanced Diet

Food is essential to living things because it supplies them with energy.

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Carbohydrates needed for energy

Fats needed for energy

Proteins needed for growth and repair

Minerals for healthy growth

Vitamins for healthy growth

Fibre to prevent constipation

Water to prevent dehydration

Body Mass Index

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Body Mass Index (BMI) is a way to show if someone is overweight or underweight.

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It is calculated by

BMI = mass (kg)

height2 (m2)

BMI What it means

<18.5 Underweight

18.5 – 25 Ideal

25 – 30 Overweight

30 - 40 Obese

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Deficiencies

Protein deficiency

In children, a lack of protein results in Kwashiorkor. Muscles waste away because the protein in them is used for energy. The belly swells.

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Vitamin deficiency

A lack of vitamin C can lead to scurvy resulting in poor skin, tender gums, loss of teeth

A lack of vitamin D can lead to rickets or osteoporosis, a weakening of the bones

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Eating Disorders

Sometimes people use food to make them feel more in control. These are called eating disorders.

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Anorexia Nervosa

People who restrict what they eat and sometimes starve.

Can lead to extreme weight loss, constipation, dizziness, poor circulation, brittle bones, irregular periods (in girls)Bulimia Nervosa

People make themselves vomit or take laxatives to prevent food digestion.

Can lead to tooth decay, bad breath, hair loss, poor skin, increased risk of heart problems, irregular periods (in girls)

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Digestion Physical digestion includes chewing to break food up.

Chemical digestion uses enzymes to break down large insoluble molecules into smaller soluble molecules.

Enzymes (carbohydrases) are added in the mouth to break carbohydrates into sugar.

In the stomach, protease enzymes break down proteins into amino acids. Acid kills bacteria and provides conditions for the enzymes to work.

The pancreas produces carbohydrases, proteases and lipases

Bile from the liver is added to emulsify fats and make them easier to digest.

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Types of diseases

Malaria

Defending against pathogens

Immunity

Drug testing

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Types of Diseases

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Infectious diseases are caused by micro organisms which attack the body. They are spread from one person to another.Pathogens are disease causing micro organisms

Fungi can cause athletes foot

Viruses can cause flu

Bacteria can cause cholera

Protozoa can cause dysentery

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Non infectious diseases e.g. cancer, are not passed from person to person. They can be caused by poor diet or genetic inheritance.

Malaria

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This is a disease caused by a parasite that lives in the blood. The human body and other animals are the host.

The parasite is spread by mosquitoes.

Mosquitoes are vectors (animals that spread disease from one animal to another)

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The mosquito sucks up the blood of an animal that has the parasite.

When the mosquito sucks the blood of another animal, the parasite is passed on into the bloodstream.

Defending Against Pathogens

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The body has lots of defences to prevent pathogens eg skin, mucus in respiratory system, blood clots, acid in the stomach.

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Once they are inside the body we depend on antibodies.

Each pathogen has its own antigen. Antibodies are produced by our body for each antigen.

The antibodies lock onto the antigens and kills the pathogen.

Immunity

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It can take several days for our body to produce antibodies. During this time we can become very ill.

Natural immunity

Once we have made an antibody, it can be made much quicker the next time it is needed.

Immunisation

This is being injected with a harmless form of the disease that has antigens in it. They trigger the production of antibodies, so if we catch the disease in the future we can produce antibodies quicklyPassive immunity

When antibodies are just injected into a body and not made by the person themselves

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Drug Testing

New drugs have to be tested to make sure they are effective and safe.

A drug can be tested using computer models, animals and human tissue.

It must be tested on healthy volunteers. Some are given the drug and some are given a placebo (ineffective drug)

In a blind trial, the volunteers don’t know which they are taking, the drug or the placebo. This gets rid of psychological factors.

In a double blind trial, neither the volunteers or the doctors know which pill has been given. This eliminates all bias.

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Neurones

The nervous system

Voluntary action

Reflex action

The eye

Types of vision

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Neurons are cells that carry electrical signals e.g. a nerve impulse

They are long to make connections from one part of the body to another.

They branch to allow a single neuron to act on lots of other neurons.

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The central nervous system allows an organism to react to their surroundings and respond

The central nervous system (brain and spinal cord) is connected to the body via neurons. These neurons send messages all over the body.

A receptor detects changes in the environmentExamples of receptors are

in the eyes to detect light

in the tongue to detect taste

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Voluntary responses mean a person decides how to react to a stimulus. E.g. insect landing on your leg

• Receptors on skin detect insect

• Impulse sent along a sensory neurone

• Impulse received by spinal cord. Carried on to brain

• Brain decides to flick insect away

• Impulse sent down motor neurone to spinal cord

• Impulse received by muscle and causes hand to move

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Reflex Actions

These are involuntary responses which bypass the brain to give a fast, automatic response. This is to protect from harm.

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• Receptors stimulated by pin

• Impulses passed along sensory neurone

• Sensory neurone bypasses the brain to a motor neurone using a relay neurone

• Impulse received by muscle

• Hand moves away from the pin

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The Eye• The eye focuses light onto

the retina

• The cornea and lens refract light so they converge at a single point

• The light sensitive receptor cells in the retina are stimulated

• This causes nerve impulses to pass along neurones to the brainLong sight – light not in focus

by the time it reaches the retina

Short sight – light focuses before it reaches the retina

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Types of Vision

There are two main types of vision

binocular vision and monocular vision

Binocular vision

Some animals e.g. humans have eyes positioned close together on the front of their heads. This is binocular vision and is usually found in predators. The animal can judge distance quite accurately.

Monocular vision

Some animals have eyes set on either side of their heads. Usually found on prey. The animal can see each side, in front and behind but cannot judge distance well.

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Types of drugs

Drug classification

Smoking

Effects of smoking

Alcohol

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Types of Drugs

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Drugs are chemicals that affect the way the body work.

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Drug Examples Effect

Stimulants Caffeine, nicotine, ecstasy

Increase brain activity, increased alertness, addictive

Depressants/ sedatives

Alcohol, solvents

Decreased brain activity, tiredness, slows down reactions, forgetfulness

Painkillers Aspirin, heroin, ketamine

Reduces pain, can be addictive

Performance enhancing

drugs

Anabolic steroids

Increased muscle development

Hallucinogens Cannabis, LSD Distorted perceptions, sensations

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Drug Classification

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In the UK, illegal drugs are classified into three classes

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Class A drugs

These are the most dangerous drugs such as heroin, cocaine, ecstasy. They can carry prison sentences (up to 7 years) for possession Class B drugs

These include amphetamines (speed). Possession can lead to prison sentences of up to 5 years.

Class C drugs

These are less dangerous and have lower penalties. E.g. steroids, cannabis, tranquillisers

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Smoking

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Cigarettes contain nicotine, which is very addictive.

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When cigarettes are burned, carbon monoxide is produced. This is a poisonous gas that prevents the blood carrying oxygen around the body.

They also contain tar. This is carcinogenic. It damages the lungs and can cause lung cancer.

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Effects of Smoking

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The trachea, bronchi and bronchioles are lined with mucus and small hairs called cilia to trap dirt.

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Cigarette smoke contains chemicals that stop the cilia from wafting mucus from the lungs to the throat. The mucus accumulates in the lungs leading to a smokers cough.Smoking can also damage air sacs which can lead to emphysema.

Build up of mucus in bronchi can become infected and cause bronchitis

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Alcohol

Alcohol is a depressant.

Short term effects can lead to lack of balance, blurred vision, slurred speech, poor judgement.

Excess alcohol can lead to unconsciousness, coma and even death.

Long term effects can be cirrhosis (liver damage) or brain damage.

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Homeostasis

Vasodilation and vasoconstriction

Hormones

Hormones and the menstrual cycle

Controlling fertility

Diabetes

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Homeostasis

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Homeostasis is the maintenance of a constant internal environment

This means keeping conditions the same inside the body

It is achieved by balancing what goes in the body and what comes out of the body

Vasodilation and Vasoconstriction

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Vasodilation is the widening of the blood vessels which run close to the surface of the skin.

In hot conditions, the capillaries widen causing greater heat loss. This means more heat is lost from the surface of the skin.

Vasoconstriction is the narrowing of the blood vessels

In cold conditions the capillaries constrict to reduce heat loss. This means less heat is lost from the surface of the skin.

Hormones

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These are chemicals released by the endocrine glands.

They are released into the bloodstream and travel around to their target organs.

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In females, the hormones oestrogen and progesterone are released by the ovaries.

In males, testosterone is released by the testes.

In both, the hormone insulin is released by the pancreas.

Hormones and the Menstrual Cycle

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Whilst a woman is fertile the lining of her uterus is replaced every month.

Two hormones are involved in the cycle

• Oestrogen stimulates the repair of the uterus wall and thickening of uterus lining

• Progesterone maintains the uterus lining until the end of the cycle

• Oestrogen and progesterone work together to control fertility

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Controlling FertilityHormones can be used to control fertility in women

Fertility drugs

Hormones stimulate the release of eggs

Contraceptive pills

Hormones prevent the release of eggs from the ovaries and reduce fertility

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DiabetesSome people suffer from diabetes.

They do not produce enough insulin.

Insulin converts excess sugar into glycogen which is stored in the liver.

Controlling diabetes

• Watch they do not eat too much sweet food

• May inject the hormone insulin

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DNA

Reproduction

Variation

Genes on or off?

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DNA

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DNA codes all the information needed to make new human beings. It can copy itself so information can be passed on. It is small enough to be stored in the nucleus of every cell.

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DNA molecules are two strands coiled to form a double helix.

Instructions on DNA are in the form of a genetic code of four bases (A T C G)

This code controls the development of the related characteristic by giving the order of the proteins

Bases always pair up in the same way – A with T, C with G

Reproduction

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Humans have 23 pairs (46 in total) of chromosomes in body cells.

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In sex cells, there is only 23 single chromosomes

During sexual reproduction, the sperm and egg fuse to produce a cell with 46 chromosomes.

In asexual reproduction, all the genes come from one parent. The offspring genetically identical and is called a clone.

Variation

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Variation is differences between individuals.

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Genetic variation can be caused by:

• Mutations which alter the gene

• Random fusion of an egg with one out of millions of sperm

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Genes On or Off?

Different cells in the body use different proteins

Example

All nerve cells have a full copy of your DNA but only use the the genes that tell them how to be a nerve cell. All the others are switched off

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Inheritance and alleles

Genetic diagrams

Inherited diseases

Mutations

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Inheritance and Alleles

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Genes can have different alleles. They are recessive or dominant.

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A dominant allele controls the development. Only one is needed to inherit that characteristic.

A recessive allele only controls development if two are present.

If both chromosomes contain the same allele, it is a homozygous pair.

If chromosomes in a pair are different, it is a heterozygous pair.

Genetic Diagrams

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These are used to show all combinations of alleles.

Capital letters are used for dominant alleles.

Lower case letters are used for recessive alleles.

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B b

b Bb bb

b Bb bb

mother

father

Inherited Diseases

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Some diseases are caused by a “faulty” gene which means they can be inherited.

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Sickle cell anaemia

Causes red blood cells to be sickle shaped meaning oxygen deficiency and circulatory problems.

Caused by a recessive allele.

Cystic fibrosis

Causes cell membranes to produce too much mucus resulting in blocked airways.

Caused by a recessive allele.

Mutations

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New variations of genes can form from mutations (changes)

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This can happen when exposed to

• Ultraviolet light

• Radioactive sources

• X-rays

• Certain chemicals

Mutations are usually harmful but can sometimes be beneficial

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