B1- Understanding Ourselves


Fitness and Blood Pressure

Blood is pumped around the body under pressure:

  • By the contractions of the heart. Blood leaves the heart and flows through arteries which split into thousands of tiny capillaries which take blood to every single cell
  • Blood pressure is at its highest when the heart contracts which is systolic pressure. When the heart relaxes the pressure is at its lowest. This is called diastolic pressure
  • Blood pressure is measured in mm of mercury
  • In a healthy person this shouldn't be higher than about 135 (systolic) and 85 (diastolic)
  • Other factors could increase blood pressure are: smoking, being overweight, drinking too much alcohol, stress

High or Low Blood Pressure can cause health problems

  • If it is too high then blood vessels can burst and this can lead to strokes, brain damage
  • Blood pressure can be decreased with lifestyle changes such as a balanced diet or exercise
  • Low blood pressure is less common but it causes poor circulation which can cause dizziness and fainting
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High Blood Pressure and Heart Disease

Smoking can increase blood pressure

  • Carbon Monoxie which combines with haemoglobin in red blood cells reduces the amount of oxygen they can carry, the heart rate increases and the more it contracts it increases pressure
  • Nicotine increases the heart rate and the heart then contracts more often

A poor diet can lead to heart disease

  • Cholesterol is a fatty substance so eating a diet high in saturated fat is linked to high levels of cholesterol in the blood
  • We need cholesterol for making cell membranes. If you get too much it builds up in our arteries
  • This forms plaques in the artery wall ehich narrow the arteries and this restricts the flow of blood which can lead to a heart attack
  • We need salt as part of a healthy diet but eating too much can damage arteries which build up plaques which can lead to a heart attack
  • The heart muscle is supplied with blood from the coronary arteries so if they become narrowed it constricts the flow and the heart receives less oxygen. Thrombosis also restricts blood flow which might block flow completely and the heart muscle will be cut off from oxygen supply
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Eating Healthily

A balanced diet supplies all your essential nutrients

  • Carbohyrates are made up of simple sugars like glucose and are converted to fats to provide energy
  • Fats are made up of fatty acids and glycerol and provde energy and provide insulation
  • Proteins are made up of amino acids and are needed for growth and repair

Energy and Nutrient needs vary between people

  • Age= Children and teenagers need more protein for growth and older people need calcium
  • Gender= Females need more iron to replace that lost in menstrual blood
  • Physical Activity= Active people need more protein for mucld development and carbs for energy

Some people eat a different diet

  • For religious regions
  • Personal Reasons: vegetarians, vegans, etc
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Diet Problems

Eating too little protein can cause problems

  • It can caused something called kwashiorkor, a common symptom is a swollen stomach and this is quite common in developing countries
  • You calculate a person's estimated requirement by doing EAR= 0.6 x body mass (kg)
  • It varies because teenagers need more protein because they are still growing and it changes after pregnancy to help produce milk

Eating disorders

  • Some psychological disorders like anorexia and bulimia cause a poor diet and other illnesses such as kidney failure, liver failure, heart attacks, muscle wastage, low blood pressure. These disorders can be fatal


  • Can be an index to tell if someone is under or over weight. However it doesn't consider muscle so athletes can come out as fat or overweight
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Infectious Disease

Can be caused by pathogens

  • Fungi- athlete's foot is caused by fungi
  • Bacteria- cholera is caused by bacteria
  • Viruses- flu is caused by a virus
  • Protozoa- dysentry is caused by protozoa

Malaria is an example of a protozoa

  • Malaria is an example of a protozoa and is carried by mosquitos. The protozoan is a parasite and they carry it without actually getting it themselves. When they feed off an infected animal they carry it and infect another animal by inserting it into the things blood vessels
  • The areas of water where they lay their eggs can be drained or sprayed with insecticides
  • Fish can be introduced into the water to eat mosqito larvae
  • People can be protected usng insecticides and mosquito nets
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The Immune System

Consuming them

White blood cells can engulf foreign cels and digest them

Producing Antitoxins

Antitoxins counter the effect of any poisons produced by the invading pathogens

Producing Antibodies

  • Every pathogen has unique molecules on the surface of its cells, no two pathogens have the same ones, these molecules are called antigens
  • When your white blood cells come from a foreign antigen and they'll start to produce proteins called antibodies which lock on to and kill the new invading cells
  • Antibodies are then produced rapidly and flow all round the body to kill all similar bacteria or viruses
  • Some white blood cells stay around in the blood after it has been fought off. These are called memory cells. If the person is infected again then these cells will make antibodies and kill it
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Preventing and Treating Infectious Disease

Vaccination (Immunisation)

  • When you get infected with a new pathogen our white blood cells may take a while to produce antibodies and in this time we can get very ill, or even die
  • We can be immunised against some e.g, polio. It involved injecting dead or inactive pathogens into the body which carry antigens so even though they are harmless they trigger a response
  • Active immunity is when the immune system makes its own antibodies and is permanent. Passive immunity is where you use antibodies made by another organism for example passed through breast milk, this tends to be temporary

Benefits and Risks associated with Immunisation

  • Stops you getting ill, it won't spread as easily
  • You can have some side effects such as swelling or redness, you can't have a vaccine if you are already ill and some people think that immunisation can cause other disorders
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Cancer and Drug Development

  • Benign: This is where the tumour grows until there is no more room and the cells stay where they are, this type isn't normally dangerous
  • Malignant: This is where the tumour grows and can spread to other sites in the body, this are dangerous and can be fatal

Drugs developed to treat disease need to be tested

  • Computer models are often used at first to stimulate a human's response to a drug
  • The drugs are then developed further by testing on human tissues
  • The last step is to develop and test the drug using animals. The law in Britain states that the new drug must be tested on two different live animals

After the drug has been tested it is tested on humans

  • This is done through a clinical trial where there are two groups of patients. One is given the drug and the other are given a Placebo (a fake) so scientists can see if it makes a difference. Or they use it and compare it to a drug which is already avaliable
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Drugs: Use and Harm

  • DEPRESSANTS: e.g. alcohol, solvents, temazepam. These decrease the activity of the brain which slows down the responses of the nervous system, causing slow reaction and poor judgement
  • STIMULANTS- e.g. nicotine, caffeine, ecstacy. These increase the brain activity and make you feel more alert and awake
  • PAINKILLERS- e.g. aspirin and paracetamol. Mild painkillers like aspirin work by reducing the number of 'painful' stimuli at the nerve endings near an injury
  • PERFORMANCE ENHANCERS- e.g. anabolic steriods. These are taken by athletes as they help build muscle and allow the athletes to train harder but they are banned by most organisations
  • HALLUCINOGENS- e.g. LSD. They distort what's seen and heard by altering pathways that the brain sends messages along

Some drugs are illegal

Class A drugs include heroin, LSD, ecstacy and cocaine. Class B drugs contain cannabis and speed. Class C drugs contain anabolic steroids and tranquilisers.

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Smoking and Alcohol

Alcohol is a depressant

  • Many people thing that it in moderation helps socialisin and relaxing however it is poisonous and is broken down in the liver but its products are toxic. Over time these can cause the death of the liver cells and form scar tissue that stops blood reaching the liver. Cirrhosis. If it can't clean the blood then it can build up and damage the rest of the body

Smoking can cause all sorts of illnesses

  • Heart disease: carbon monoxide reduces th oxygen carrying capacity of the blood, if the heart muscle doesn't receive enough oxygen it can lead to a heart attack
  • Lung, throat, mouth and oesophagul cancer: tar from the smoke collects in the lungs and is full of toxic chemicals causing malignant tumours
  • Smoker's cough because of damage to the cilia on the epithelial tissue lining the trachea, bronchi and bronchioles which encourages mucus to be produced
  • Low birth weight babies: low oxygen in the blood of pregnant women can deprive the foetus of oxygen leading to a small baby at birth
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The Eye

  • The cornea refracts light into the eye
  • The iris controls how much light enters the pupil
  • The lens also refracts light, focussing it onto the retina
  • The retina is the light sensitive part and it is covered in receptors called rods and cones
  • Rods are more sensitive in dim light but can't colour
  • Cones are more sensitive to different colour's and not so good in dim light

Long-Sighted and Short-Sighted

  • Long-sighted people are unable to focus on near objects which occurs when the lens is the wrong shape and doesn't bend light enough or the eyeball is too short. Correct with glasses or convex lenses
  • Short-sighted people are unable to focus on distant objects because the lens is the wrong shape and bends light too much or the eyeball is actually too long. Correct with glasses or concave lenses 
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Neurons and Reflexes

The Central Nervous System (CNS)

  • It consists of the brain and the spinal chord, the nervous system is made up of the three types of neurone- sensory neurones, relay neurones and motor neurones
  • When you detect a change your sensory neurones carry information from receptors to the CNS
  • The CNS then sends information to an effector along a motor neurone
  • The job of the CNS is to coordinate the information

Reflex Actions stop us from injuring ourselves

  • The nervous system uses electrical impulses to allow very quick responses, they are automatic
  • The conscious brain isn't involved in a reflex arc. The sensory neurone connects to a relay neurone in the spinal chord which links directly to the right motor neurone
  • Reflex actions often have a projectile role, e.g. snatching back your hand after touching a hot plate before you even realise you have done it
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Electrical Impulses

  • The electrical impulse is passed along the axon of a cell
  • Neurones have branched endings so they can connect with other neurones
  • They have a sheath along the axon that acts as an electrical insulator which speeds up the electrical impulse
  • They're long which speeds up the impulse
  • The connection between two neurones is called a synapse which is a very tiny gap
  • The electrical impulse tiggers the release of transmitter chemicals which diffuse across the gap
  • These chemicals bind to receptor molecules in the membrane of the nex neurone which sets off a new impulse
  • Stimulant drugs increase the amount of transmitter chemical at some synapses which increases the frequency of impulses along neuron 2
  • Depressants bind with receptor molecules on the membrane of neurone 2 blocking the electrical impulse, this decreases brain activity
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Conditions in you body need to be kept steady so that cells can function properly:

  • Levels of CO2= respiration constanty produces CO2 which we need to get rid of
  • Water content= you need to keep a balance between the water you gin and the water we wee, sweat and breathe out
  • Body Temperature= you need to get rid of excess body heat when we are hot but retain heat when the environment is cold

Negative Feedback...... Changes in the environment trigger a response that counteracts the changes e.g. a rise in body temperature causes a response that lowers body temperature. This means that the internal environment tends to stay around a norm, the level at which the cells work best. This only works within certain limits if the environment changed too much then it might not be possible to counteract it

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Homeostasis and Body Temperature

All enzymes have an optimum temperature which they work at, 37'c. There is a thermoregulatory centre in the brain which acts as your own personal thermosat. It contains receptors that are sensitive to the blood temperature in the brain, it receives impulses from the skin that provide information about skin temperatures. The brain uses the nervous and hormonal systems to initiate control mechanisms:

When you're too hot

  • Hairs lie flat, lots of sweat is produced (when it evaporates it transfers heat to environment which cools us down) and blood vessels close to the skins widen which allows more blood to flow near to the surface so it radiates more heat to the surroundings. VASODILATION

When you're too cold

  • Hairs stand on end to trap an insulating layer, little sweat is produced, blood vessels constrict VASOCONSTRICTION so less heat can be transferred from the blood to the surroundings and we shiver which generates heat in our muscles
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Controlling Blood Sugars

Insulin controls Blood Sugar levels

  • Eating foods containing carbohydrates put glucose into the blood from the gut, normal respiration in cells removes glucose from the blood and vigorous exercise removes alot of glucose from the blood
  • The level of glucose in the blood must be kept steady and this is measured by the pancreas using insulin. Blood glucose level too high- insulin is added, blood glucose level too low- insulin not added.
  • Insulin is a hormone which travels in the blood


  • Type 1 diabetes means the pancreas produces little or no insulin which means their glucose level could rise to a level that may kill them
  • Type 2 diabetes is when someone is resiliant to insulin and so is controlled through their diet
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Genes and Chromosomes

  • Most cells in our body have a nucleus which contains our genetic material in the form of chromosome
  • In most animal cells chromosomes come in pairs but different species have a different number of pairs. A human has 23 pairs but a guinea pig has 32 pairs
  • Chromosomes carry genes and different genes control th development of different characteristics
  • A gene is a short length of the chromosome which is quite a long length of DNA
  • The DNA is coiled up to form the arms of the chromosome
  • There can be different versions of the same gene which give different versions of a characteristics. The different versions of the same gene are called alleles instead of genes
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