infection and response

• risk factors for disease:

  • certain genetics
  • age
  • gender
  • smoking
  • excessive drinking
  • lack of excercise
  • sexual habits
  • drug taking
  • ionising radiation
• anaemia is a lack of iron
• kwashiorkor is a lack of protein
• scurvy is a lack of vitamin c
• night blindness is a lack of vitamin A
• rickets is a lack of vitamin D
• equation for BMI is mass (kg)/height² (m)
• generally, a higher BMI means a greater risk of medical problems. however it does not take into account bone density, racial and sex differences, etc.
• tar causes cancer of the lungs, mouth and throat. it also coats the surface of bronchi and alveoli, preventing gas exchange
• hydrogen cyanide is a toxic, poisonous gas that causes cells in the lungs to die.
• carbon monoxide stops oxygen from being carried to cells as it binds to haemoglobin in the blood. it is bad for pregnant mothers as the baby can't develop, leading to stillbirths or premature births.
• nicotine is highly addictive. it also causes an increase in heart rate and makes platelets sticky, causing blood clots.
• effects of excessive drinking:

  • cirrhosis of the liver (destroys liver tissue)
  • cancer (alcohol is a carcinogen)
  • brain structures are lost as brain becomes soft and pulpy
• ionising radiation damages living cells by penetrating the cells and damaging the chromosomes, eg light from the sun, radioactive materials, x-rays
• coronary heart disease is a non-communicable degenerative disease. coronary arteries which run across the heart to deliver glucose and oxygen to cardiac muscle become blocked by fatty plaques and blood clots caused by saturated fats and cholesterol. this reduces aerobic respiration - less energy means atria and ventricles cannot contract with as much force. cardiac muscle cells die and cardiac arrest can occur.
• stents are inserted into the artery to increase the size of the lumen to increase blood flow. however the blockage can still reform.
• statins reduce cholesterol levels which protects all arteries in the body. however there are side effects such as nausea, headaches, muscle pain.
• a coronary artery bypass graft is when a blood vessel is taken from somewhere else in the body to divert blood around blocked parts of coronary arteries. however there is a risk of anesthetic and major surgery.
• a heart transplant is when a donor heart and/or lungs us put in. however it takes time to find a donor, there is a chance of rejection, and the risk of major surgery.
• an artificial heart is used short term whilst waiting for a transplant, or to allow the heart to rest whilst recovering.
• there are 4 valves in the heart - bicuspid, tricuspid, and semi-lunar valves. some do not open fully - this means not enough blood passes through and can lead to a build up of pressure in chambers. some can become leaky - leads to a decrease in blood pressure.
• solutions to faulty heart valves:

  biological valves - no anticoagulant is needed, no clicking noises, but only last 8-10 years

  mechanical valves - last 20 or more years, however lifelong anticoagulation medication is needed and there is an audible clicking noise.
• pacemakers are found on the right atrium wall. it sends electrical impulses to cardiac muscle to contract - sets a normal heart rhythm. sometimes heart beats too slowly, too fast (can be fixed using Beta-blockers), or skips a beat. an artificial pacemaker can be inserted under local anaesthetic with few complications. however the immune system may reject it.
• cancer:

  • cells in our bodies divide by mitosis and grow in a sequence called the cell cycle
  • cancer occurs when the control of the cycle is lost and cells grow rapidly in an abnormal way to form a tumour.
• benign tumours are contained in one place. they do not invade the body but grow very large and quickly, putting pressure on other organs and causing damage.
• malignant tumour are when the cells spread around and invade healthy tissues. clumps of the primary tumour can break off and travel in bloodstream to other parts of the body to form secondary tumours. the cells grow quicker and live longer than other body cells to compete with healthy cells for oxygen and nutrients. healthy cells die and organs and tissues are damaged.
• causes of cancer:

  • certain genetics
  • mutation (random changes to DNA of cells. some carcinogens such as asbestos and tar can trigger formations of some tumours.
  • ionising radiation (UV light, X rays)
  • infectious diseases (eg HPV causes cervical cancer)
• treating cancer:

  1. radiotherapy - cancer cells are killed by targeted doses of radiation which stop mitosis, but can also damage healthy cells
  2. chemotherapy - chemicals used to stop cells dividing (they 'self destruct')
  3. immunotherapy - helps immune system by stimulating or boosting natural defences by using substances either made in the body or in a laboratory
• cell division is important as organisms need new cells to grow, replace worn out cells, and to repair damaged tissue.
• cell division:

  • the nucleus of each cell in your body contains 46 chromosomes (23 pairs) made of DNA molecules
  • each chromosome carries a large number of genes (a short section of DNA that codes for a particular characteristic)
• mitosis

  A) divide

  B) DNA

  C) chromosome

  D) membrane

  E) line up

  F) chromosomes

  G) pulled

  H) cytoplasm

  I) divide

  J) identical

  
• cell cycle

  A) mitosis

  B) cell growth

  C) DNA synthesis

  D) s phase

  E) cell growth

  F) G2

  G) G1

  H) M

  
• pathogens are microorganisms that cause communicable diseases. they spread by direct contact, water/air, or vectors. spread can be reduced by isolating infected individuals and vaccinations. types of pathogens are viruses, protists, bacteria and fungi.
• a virus is an infectious organism that replicates inside the cells of living hosts, causing damage
• bacteria produce toxins that cause inflammation and damage cells and tissues in the body
• the immune system:

  • white blood cells defend against pathogens through phagocytosis and the production of antibodies and toxins
• lymphocytes:

  • lymphocytes recognise specific antigens on invading pathogens
  • they produce antibodies which cause the pathogens to stick together, making it easier for phagocytosis to take place
  • they can also produce antitoxins to neutralise toxins from pathogens
• vaccinations are when small quantities of dead or inactive forms of a pathogen are injected into the body. white blood cells detect the antigens on the pathogen, then produce antibodies to fight it. the antibodies attach themselves to the pathogen and memory cells remember the shape of the antigen. white blood cells instantly recognise the live pathogens when they next enter the body and produce antibodies immediately to kill the pathogen to stop you getting ill.
• antibiotics, eg penicillin, are medicines that kill bacteria inside the body (not viruses). however MRSA is a strain of bacteria which is resistant to antibiotics, therefore:

  • doctors should not prescribe antibiotics unless they are really needed
  • patients must complete their course of antibiotics so all bacteria are killed and none survive to form resistant strains
• infective bacteria reproduce quickly inside us, giving off toxins which can damage tissue and make us feel ill