1 - My Family
Health professionals use their knowledge of physiology, biochemistry and drugs to diagnose and treat disease and illness in our families and friends. They need to be aware of how humans respond to internal and external changes and how we regulate our internal systems, in order to treat problems like diabetes.
Researchers in pharmaceutical companies have developed medicines to treat diseases such as diabetes. Biochemists work alongside doctors and help them to understand some of the chemistry of our body functions, including reactions like neutralisation of stomach acid.
Geneticists consider how genes determine the structure and function of organisms and use this knowledge to explain differences between family members. Their work may lead to treatments and possible cures for inherited disorders.
1.1 Control of body system
Candidates need to understand that:
To stay healthy, the body must keep itself at the right temperature, and control the sugar content in the bloodstream. The healthy body detects external changes using sense organs and then processes this information in the brain. The nervous system then coordinates a response to this information, causing the body to make physiological changes.
Although the body is able to regulate itself by the use of these automatic systems, health professionals realise that personal lifestyle is very important in staying healthy.
Candidates need to:
1. Give examples of receptor cells that detect stimuli (light, sound, smell, taste, touch, heat).
2. Describe how information from receptors passes along cells (neurones) in nerves to the brain. The brain coordinates our response.
3. Know that some responses to stimuli are automatic and rapid and are called reflex actions.
4. Describe how reflex actions involve three neurones called sensory, relay and motor neurones.
5. Explain how longitudinal waves travel from vibrating objects to our ears for us to hear sounds.
6. Know that the human hearing range is 20–20 000 Hz.
7. Know that the body needs to maintain a constant internal environment and that this is called homeostasis.
8. HT only: explain the principle of negative feedback in maintaining a constant internal environment.
9. Know that chemical substances called hormones control many processes within the body. Hormones are secreted by glands and are transported to their target organs in the bloodstream.
10. Explain how the hormone insulin controls blood glucose levels. High blood glucose levels are a symptom of diabetes. Candidates should be aware that some forms of diabetes (Type 2 diabetes) may be controlled by a change in lifestyle (diet and exercise). Type 1 diabetes is controlled by insulin dosage and is sometimes termed insulin-dependent diabetes. Candidates should be able to describe how blood glucose levels are monitored and controlled by cells in the pancreas:
(a) if the blood glucose concentration is too high, the pancreas releases the hormone insulin into the blood,
which causes the liver to remove glucose from the blood and store it as insoluble glycogen
(b) HT only: if the blood glucose concentration is too low, the pancreas releases glucagon, which
causes the liver to convert glycogen back to glucose and release it into the blood.
11. Explain how the body maintains a constant temperature, using the thermoregulatory centre in the brain:
(a) by increasing or decreasing the amount of sweating, which cools the body by evaporation
(b) by dilating the blood vessels supplying the skin capillaries, increasing the blood flow to, and consequently the amount of heat lost from, the skin
(c) by constricting the blood vessels supplying the skin capillaries, decreasing the blood flow and the amount of heat lost.
Within this context, candidates should be able to use scientific data and evidence to discuss, evaluate or suggest implications of the following:
■ the environmental, social and health implications of loud sounds (eg from MP3 players or night clubs)
■ the social, economic and health implications of diabetes
■ the personal and social choices in lifestyle in terms of a balance of risk and benefit to health
■ what happens when the normal physiological processes go wrong.
1.2 Chemistry in action in the body
Candidates need to understand that:
Our bodies only function because many complex chemical reactions are continuously occurring. For example, our stomach contains hydrochloric acid, which helps enzymes to break down the protein that we eat and also helps to protect us from infection from microbes in our food. Sometimes excess acid can make us feel uncomfortable and may cause heartburn and nausea.
Pharmacologists use their knowledge of neutralisation reactions to monitor and control stomach acid using antacids. They test the effectiveness of antacids in terms of how efficiently they neutralise excess stomach acid before they are sold to the consumer.
Candidates need to:
1. Know that the body functions properly due to a series of complex chemical reactions.
2. Name some hazards of acids and bases and some control measures that can be put in place to minimise risks from them.
3. Know that acids are neutralised by reaction with oxides, hydroxides or carbonates to form salts and other products.
4. Know the patterns in the reactions of soluble hydroxides and carbonates with acids.
5. Describe how a neutralisation reaction involves an acid and an alkaline substance reacting to form a salt and water:
(a) hydrogen ions (H+) make solutions acidic
(b) hydroxide ions (OH–) make solutions alkaline
(c) HT only: this reaction can be represented by the equation: H+(aq) + OH– (aq) ➞ H2O(l)
6. Understand that the stomach works most effectively in acid conditions by helping to break down food.
7. Explain how an antacid neutralises excess stomach acid to help to treat heartburn and nausea.
Within this context, candidates should be able to use scientific data and evidence to discuss, evaluate or suggest implications of the following:
■ the effectiveness of a range of antacid products
■ the issues of testing new drugs on animals and humans.
1.3 Human inheritance and genetic disorders
Candidates need to understand that:
Our families show similarities and differences due to genetic and environmental causes. Inside our cells there is a nucleus containing chromosomes and genes, which determine our characteristics. Sometimes we inherit faulty genes, which cause genetic disorders. Geneticists working on the human genome project are trying to improve treatments and develop cures for these genetic disorders.
Candidates need to:
1. Know that simple animal cells have a nucleus, cytoplasm and cell membrane.
2. Know that the nucleus of a cell contains chromosomes:
(a) chromosomes carry genes, which control the characteristics of the body
(b) each chromosome carries a large number of genes.
3. Know that differences in the characteristics of individuals (variation) may be due to genetic causes or environmental causes or a combination of both.
4. Know that genes have different forms called alleles, which produce different characteristics.
5. Describe the mechanism of monohybrid inheritance where the dominant and recessive alleles are given.
6. Know that cystic fibrosis, sickle-cell anaemia, haemophilia and polydactyly are genetically inherited disorders.
Within this context, candidates should be able to use scientific data and evidence to discuss, evaluate or suggest implications of the following:
■ the use of current research in the treatment of genetic disorders
■ the likelihood of a genetically inherited disorder occurring
■ the use of genetic screening.
7. Candidates should be able to give examples of substances used as antacids (sodium bicarbonate, magnesium hydroxide, calcium carbonate, aluminium hydroxide) and write word equations to illustrate neutralisation. Higher Tier candidates will be expected to write balanced symbol equations.
Suggestions for practical work that could be used to support Theme 1
It is the responsibility of the centre to be aware of the health and safety implications of any practical work, and to ensure that risk assessments for practicals are carried out.
■ Measure reaction times using metre rules, stop clocks or ICT.
■ Demonstrate the speed of transmission by nerves: candidates stand in a semi-circle, holding hands and squeezing with eyes closed.
■ Use blindfolds and open paper clips to test pressure points and skin sensitivity.
■ Demonstrate the knee-jerk reaction.
■ Test reflexes: elbow, knee, foot, pupils.
■ Class hearing test, using oscilloscope equipment.
■ Investigate the effect of acid on various objects left for a few days.
■ Neutralisation titration.
■ Investigate reaction of carbonates with acids.
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