3.3.10Interactions with the Environment
Interactions Between Different Types Of Disease
5 min read 6 parts Lesson 27 of 27 Unit quiz
Section 1 of 6How diseases link together
Interacting diseases
Weak immune system
- Weak immune system A defect in the immune system makes infectious diseases more likely and harder to fight.
- The defect may be inherited or caused by an infection such as HIV.
Viruses and cancer
- Viruses and cancer Some viruses living in cells can trigger the cells to become cancerous.
- The virus changes how the cell controls its division, so it divides uncontrollably to form a tumour.
Immune reactions and allergy
- Immune reactions and allergy An overactive immune response that began with a pathogen can lead to allergies.
- Allergies can then trigger asthma or skin rashes.
Physical and mental health
- Physical and mental health Serious physical illness can lead to depression and other mental illness.
- Mental illness can in turn make a person less likely to look after their physical health.
Section 2 of 6Worked examples
| First problem | Linked problem | Explanation |
|---|---|---|
| HIV infection | Pneumonia and other opportunistic infections | Fewer lymphocytes circulate, so the immune system cannot fight other pathogens |
| HPV infection | Cervical cancer | The virus infects cells of the cervix and can make them divide uncontrollably |
| Hepatitis virus | Liver cancer | Some strains damage liver cells and promote cancer |
| Overactive immune response | Skin rashes and asthma | The immune system reacts strongly to harmless substances |
| Long-term serious illness | Depression | Pain, worry and loss of independence affect mental health |
| Cancer treatment | Increased infections | Chemotherapy lowers white blood cell numbers, weakening defences |
Section 3 of 6A chain from infection to complication
1Pathogen infects
- Pathogen infects For example a virus enters body cells and begins to reproduce.
2Cells or defences altered
- Cells or defences altered Infected cells change, or white blood cell numbers fall, so the body protects itself less well.
3Second condition develops
- Second condition develops Cancer, repeated infection or an allergy may appear months or years later.
4Wider impact
- Wider impact Poor health can then affect mental wellbeing, work and relationships.
Section 4 of 6Applications: reducing the risk
Vaccination
- Vaccination The HPV vaccine given to teenagers prevents infection with the virus and so lowers the risk of cervical cancer later in life.
Protecting the immunocompromised
- Protecting the immunocompromised People with weak immune systems are advised to avoid contact with infection and may be given extra medicines to protect them.
Joined-up care
- Joined-up care Doctors treating a long-term physical illness also check for signs of depression so that both conditions can be treated together.
Section 5 of 6Key terms
| Term | Meaning |
|---|---|
| Immune system | The cells and organs that defend the body against pathogens. |
| Lymphocyte | A type of white blood cell that makes antibodies. |
| Opportunistic infection | An infection that takes advantage of a weakened immune system. |
| Allergy | An exaggerated immune reaction to a harmless substance. |
| Mental illness | A condition that affects thoughts, mood or behaviour. |
| Tumour | A mass of cells that divide uncontrollably. |
Section 6 of 6Exam technique
1
Saying HIV causes pneumonia directly. It weakens the immune system, which lets other pathogens cause infection.
2
Assuming cancer is always inherited. Some cancers are triggered by viruses.
3
Treating allergies as infections. They are immune reactions to harmless substances.
4
Ignoring mental health when asked how diseases interact.
5
Thinking cancer can be passed from person to person like a cold. It is not an infectious disease.