B2 Specification

Module B2: Keeping Healthy

B2.1 How do our bodies resist infection?

1. understand that symptoms of an infectious disease are caused by damage done to cells by

microorganisms or the poisons (toxins) they produce

2. understand why, in suitable conditions such as those inside a human body, microorganisms

(eg bacteria and viruses) can reproduce rapidly to produce very large numbers

3. calculate the population growth of microorganisms given appropriate data

4. understand that white blood cells are part of the body’s immune system and can destroy

microorganisms by engulfing and digesting them or by producing antibodies

5. understand that antibodies recognise microorganisms by the antigens that they carry on their

surface, that different microorganisms have different antigens, and that a different antibody is

therefore needed to recognise each different type of microorganism

6. understand that once the body has made the antibody to recognise a particular

microorganism, memory cells can make that antibody again very quickly, therefore protecting

against that particular microorganism in the future (immunity).

B2.2 What are vaccines and antibiotics and how do they work?

1. understand that vaccinations provide protection from microorganisms by establishing memory

cells that produce antibodies quickly on re-infection

2. understand that a vaccine usually contains a safe form of a disease-causing microorganism

3. understand why, to prevent epidemics of infectious diseases, it is necessary to

vaccinate a high percentage of a population

4. understand that vaccines and drugs (medicines) can never be completely risk-free, since

individuals have varying degrees of side effects to them

5. understand that due to genetic differences, people react differently to drugs and vaccines

6. understand that chemicals called antimicrobials can be used to kill, or inhibit, bacteria, fungi

and viruses

7. recall that antibiotics are a type of antimicrobial that are effective against bacteria but not

viruses

8. understand that over a period of time bacteria and fungi may become resistant to

antimicrobials

9. understand that random changes (mutations) in the genes of these microorganisms

sometimes lead to varieties which are less affected by antimicrobials

10. understand that to reduce antibiotic resistance we should only use antibiotics when necessary

and always complete the course

11. understand that new drugs and vaccines are  first tested for safety and effectiveness using

animals and human cells grown in the laboratory

12. recall that human trials may then be carried out:

 a. on healthy volunteers to test for safety

 b. on people with the illness to test for safety and effectiveness

13. describe and explain the use of ‘open-label’, ‘blind’ and ‘double-blind’ human trials in

the testing of a new medical treatment

14. understand the importance of long-term human trials

15. understand the ethical issues related to using placebos in human trials.

B2.3 What factors increase the risk of heart disease?

1. describe the role of the heart as a double pump in the circulatory system

2. understand why heart muscle cells need their own blood supply

3. understand how the structure of arteries, veins and capillaries is related to their function

4. understand that heart rate can be measured by recording the pulse rate

5. understand that blood pressure measurements record the pressure of the blood on the walls

of the artery

6. understand that a blood pressure measurement is given as two numbers, the higher value

when the heart is contracting and the lower value when the heart is relaxed

7. understand that ‘normal’ measurements for factors such as heart rate and blood pressure are

given within a range because individuals vary

8. understand how fatty deposits in the blood vessels supplying the heart muscle can produce a

‘heart attack’

9. understand that heart disease is usually caused by lifestyle factors and/or genetic factors

10. understand that lifestyle factors that can increase the risk of heart disease include:

 a. poor diet

 b. stress

 c. cigarette smoking

 d. misuse of drugs

11. understand that regular moderate exercise reduces the risk of developing heart disease

12. relate differences in lifestyle factors in the UK and non-industrialised countries to the

prevalence of heart disease

13. understand how factors that can increase the risk of heart disease are identi ed via

epidemiological and large scale genetics studies

14. assess levels of heart disease risk, and actions that could be taken to reduce risk, when

provided with lifestyle and genetic data

15. understand that high blood pressure increases the risk of heart disease

16. understand that the misuse of drugs (eg Ecstasy, cannabis, nicotine and alcohol) can have an

adverse effect on health, including heart rate and blood pressure, increasing the risk of a heart

attack.

B2.4 How do our bodies keep a healthy water balance?

1. understand that nervous and hormonal communication systems are involved in maintaining a

constant internal environment (homeostasis)

2. understand that automatic control systems throughout the body maintain a range of factors at

steady levels and that this is required for cells to function properly

3. recall that these control systems have:

 a. receptors to detect changes in the environment

 b. processing centres to receive information and coordinate responses automatically

 c. effectors to produce the response

4. understand the principle of negative feedback

5. understand that negative feedback between the effector and the receptor of a control

system reverses any changes to the system’s steady state

6. understand that a balanced water level is important for maintaining the concentration of cell

contents at the correct level for cell activity

7. understand that water levels are controlled by balancing gains from drinks, food and

respiration and losses through sweating, breathing, faeces and the excretion of urine

8. understand that the kidneys play a vital role in balancing levels of water, waste and other

chemicals in the blood

  Candidates are not expected to recall details of kidney structure

9. understand that the kidneys balance water levels by producing dilute or concentrated urine

as a response to concentration of blood plasma, which is affected by external temperature,

exercise level and intake of  fluids and salt

10. understand that concentration of urine is controlled by a hormone called ADH, which is

released into the bloodstream by the pituitary gland

11. understand how ADH secretion is controlled by negative feedback

12. understand that alcohol results in the production of a greater volume of more dilute urine, due

to ADH suppression, which can lead to dehydration and adverse effects on health

13. understand that the drug Ecstasy results in a smaller volume of less dilute urine, due to

increased ADH production.

© OCR 2012 GCSE Additional Science