Biology - health and disease

• Health is a state of complete mental, physical and social wellbeing, not merely just the absence of disease
• Communicable diseases can be transmitted from person to person and are infectious. Non - communicable diseases cannot be transmitted from person to person and tend to be genetic/inherited.
• The presence of one disease makes the body more susceptible to other diseases because the immune system lies under pressure whilst it combats the current disease
• A pathogen is a disease causing organism - protists, virus, bacteria and fungi
• Cholera: this is a bacterial infection which causes severe diarrhoea, is spread through contaminated water and can be treated with antibiotics and ensuring you eat/drink sterile food/water.
• Malaria: this is a disease caused by a protist, it causes damage to the blood and liver (symptoms include fever and vomiting). It is spread by animal vectors (mosquitos) and can be treated with antimalarial drugs.
• Tuberculosis: this is a bacterial infection which causes damage to the lungs (symptoms include chest pains and fever). It is spread through the air and can be treated using antibiotics.
• Chalara ash dieback: this is a fungal disease which causes lesions and leaf loss in plants. It is spread through the air and can be treated by removing any ash leaf litter from around trees. It can be prevented the same way.
• HIV: this is a viral infection which destroys white blood cells (symptoms include fever, rashes, headache). This infection is spread through sexual contact/sharing of bodily fluids. It can be prevented by wearing a condom and not sharing needles. It cam be treated with antiviral medication.
• Chlamydia: a bacterial infection which can cause infertility/damage to reproductive system. (symptoms include pain in pelvic area, pain when urinating and unusual vaginal discharge). It is spread through sexual contact/sharing of bodily fluids. It can be prevented by wearing a condom and getting regular checkups. It can be treated with antibiotics.
• virus - hijacks cells, replicated inside them and hides inside them
• bacteria - multiply inside host organism and release toxins
• fungi - reproduce inside the organism by forming spores
• barrier methods: Mucus traps any dirt and pathogens. Cillia wafts away dust particles and pathogens away from the airways. Skin acts as a physical barrier to pathogens outside the body.
• Chemical defence: stomach acid has a pH of 2 and is strong enough to kill most pathogens. Lysozymes in tears/saliva destroy bacterial cells by breaking down cell walls.
• The role of the specific immune system: 1. The body is exposed to a pathogen 2. Lymphocytes detect the antigen on the pathogen and release complementary antibodies

  3. Pathogen is killed by antibodies and memory lymphocytes are produced

  4. Memory lymphocytes allow a faster and more efficient response to secondary infection
• Immunization:

  1. A patient is injected with an inactive form of a pathogen
  2. Lymphocytes in the body detect the antigen on the pathogen and release complementary antibodies
  3. Antibodies destroy the pathogen and memory lymphocytes are produced
  4. Memory lymphocytes allow a faster and more efficient response to secondary infection
  5. The patient is now immune to the pathogen
• antibiotics can only be used to treat bacterial infections because they inhibit cell processes in the bacterium but not the host organism
• Medicine development:

  1. Research and development
  2. Pre-clinical trials to test on cells and tissues in a lab, in order to check if it works
  3. Animal testing to check for side effects and safety
  4. Clinical trials - firstly tested on healthy volunteers to check for side effects and safety. Secondly, low dosage is given to sick patients and trials are continued to find the optimum dosage.
  5. Double blind trials - one group of patients gets the drug, one group gets a placebo: the results show whether the drug is more effective than the placebo
• cardiovascular disease: This is a non-communicable disease, which affects the heart and blood vessels – including things like strokes and heart attacks. This disease is usually caused by fatty deposits in the arteries, which can block them and cause blood clots – due to too high cholesterol levels. Deposits occur in areas where the artery wall has been damaged, e.g. by high blood pressure. This restricts blood flow around the body, depriving the heart muscle and brain of oxygen
• Treatments for CV disease:

  •Lifestyle changes – eating a healthy, balanced diet, low in saturated fat to lower blood cholesterol. Exercising regularly, not smoking and losing weight if necessary

  •Statins – these are drugs which reduce cholesterol levels. However, can cause side effects like muscle aches and liver damage, and must be taken for the course of the patients entire life.
• Treatments for CV disease:

  •Stents – these are tubes which are inserted into arteries to keep them open, encouraging blood flow and lowering heart attack risk. However, drugs must be taken to stop blood clotting on the stent, and the stent can irritate the artery and cause scarring.

  •Donor heart – this is the replacement of a diseased heart with a healthy heart, however, the body may reject the heart and this requires surgery
• Alcohol:

  •Releases toxins when is broken down, which causes fatty build up and inflammation in the liver – can also cause scarring, leading to cirrhosis

  •Leads to drowsiness, mood changes, impulsivity and lack of control

  •Shrinks and disturbs brain tissue
• Smoking:

  •Tar begins to coat the teeth and gums

  •Damages nerve endings in the nose – causing loss of smell

  •Damages cilia and gets carbon monoxide into the bloodstream

  •Nicotine – makes smoking extremely addictive

  •Blood vessels constrict and dangerous mutations can form on DNA
• BMI = Weight (kg)/ height (m) squared
• Waist to hip ratio = waist circumference/ hip circumference