Causes Of Disease In Humans Aqa Essay

What is disease?

  • A disease is defined as a physical or mental disorder or malfunction with a characteristic set of signs or symptoms.
  • Diseases may be caused by a single factor such as a pathogenic microorganism or be multifactorial and have many causes some of which may depend on lifestyle.


  • Pathogenic microorganisms include bacteria, viruses and fungi.
  • Each pathogen has a specific method by which it causes disease.  Some such as the influenza virus damage host cells whereas others, such as Vibrio cholera produce toxins which have a harmful effect on the body.
  • The ability of the pathogen to cause disease depends on
    • Location - what tissue is colonised
    • Infectivity - how easily a bacterium can enter the host cell
    • Invasiveness - how easily a bacterium or its toxin spreads within the body
    • Pathogenicity - how a bacterium causes disease
  • Common entry points for pathogens are the gas exchange and digestive system.


  • A healthy lifestyle involves:
    • Maintaining a healthy weight
    • Taking regular exercise
    • Eating a balanced diet
    • Drinking a limited amount of alcohol
    • Not smoking
  • Lifestyle has an effect on human health:
    • Exposure to carcinogenic chemicals (i.e. those found in tobacco smoke) or radiation (i.e. X-rays) may increase a person's chance of contracting cancer
    • Coronary heart disease is associated with diets that are rich in fat and a sedentary lifestyle
    • Alterations to a person’s lifestyle can have a dramatic effect on the likelihood of them contracting these conditions


Causes of Disease in Humans Essay examples

823 WordsFeb 24th, 20134 Pages

Causes of disease in humans
A disease is usually a medical condition that affects the body of an organism. In humans, disease is often broadly used to refer to any condition that causes pain, dysfunction, distress or death to the person affected. In this sense, it sometimes includes injuries, disabilities, disorders, syndromes, infections, etc. The most common cause of disease in humans is via pathogens; microorganisms such as viruses, bacteria, protozoa, and fungi that cause disease in humans and other species that enter the body in a number of ways. This includes the digestive system and the gas exchange system. Once inside the body, pathogens may cause disease by damaging cells or producing toxins that affect the cells in the body.…show more content…

Thrush is a yeast infection and its main symptom is causing inflammation of the general area resulting in discomfort to the host. Another pathogen that causes disease is Pulmonary Tuberculosis. Caused by bacterial infection, it’s transmitted via droplet infection in which it’s spread through sneezing or coughing and an uninfected person takes in the droplets by inhaling them into the lungs. The bacteria reproduce and destroy the lung tissue, prompting an immune response that brings the infection under control and repairs the lung damage is. However, the infection may re emerge years later as secondary TB. This occurs as in some cases as the phagocytes surround and ingest the bacteria but the bacteria have a thick waxy coat and are not killed by the white blood cells. The TB bacteria start to destroy the lung tissue, causing multiple lesions appear on the lungs called tubercles and the bacteria may spread to both lungs and to other organs such brain. The patient coughing up damaged lung tissue and blood and becoming very short of breath are just a few of the symptoms. Disease in humans can also be caused by defects in the genetic code. This results when mutations occur, which is a change in the sequence of nucleotide bases in the genetic code. The mutation, a change in the base sequence of the DNA, will mean that the mutated amino acids with code for a different polypeptide. As a result, the protein will have a different tertiary structure and

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