biology4alevel600

An infectious disease is one that can be passed between one person and another. Infectious diseases are caused by pathogens. These are usually microorganisms such as viruses, bacteria, fungi or protoctists. A non-infectious disease cannot be passed between people and is not caused by pathogens. Examples include sickle cell anaemia and lung cancer. Disease can be defined as a condition in which the body does not function normally, and which produces unpleasant symptoms such as pain, distress or feeling weak. The term disease is generally used for conditions that last for at least several days. Important infectious diseases 1. Cholera Cause Cholera is caused by a bacterium, Vibrio cholerae. Vibrio choleae. Transmission V. cholerae can enter the body in contaminated food or water. The bacteria breed in the small intestine, where they secrete a toxin that reduces the ability of the epithelium of the intestine to absorb salts and water into the blood. These are lost in the faeces, causing d

10.1  Infectious diseases 10.2  Antibiotics The infectious diseases studied in this section are caused by pathogens that  are transmitted from one human host  to another. Some, like Plasmodium that  causes malaria, are transmitted by vectors; others are transmitted through water and food or during sexual  activity. An understanding of the biology of  the pathogen and its mode of transmission is essential if the disease is to be controlled and ultimately prevented. Learning outcomes Candidates should  be able to: 10.1  Infectious diseases While many  infectious diseases have been successfully controlled in  some parts  of the world, many people worldwide are still at risk of these diseases. a)   define  the term  disease and explain the difference between an infectious disease and a non-infectious disease (limited to sickle cell anaemia and lung cancer) b)   state the name and type  of causative organism (pathogen) of each  of the following diseases: cholera,  malaria, tuberculosis (TB)

• Cholera, malaria, tuberculosis (TB), HIV/AIDS, smallpox and measles • Antibiotics Learning Outcomes Candidates should be able to: (a) define the term disease and explain the difference between an infectious disease and non-infectious diseases; (b) state names and types of causative organism of each of the following diseases: cholera, malaria, TB, HIV/AIDS, smallpox and measles (detailed knowledge of structure is not required. For smallpox (Variola) and measles (Morbillivirus) names of genus only is needed); (c) explain how cholera, measles, malaria, TB and HIV/AIDS are transmitted; (d) discuss the factors that need to be considered in the prevention and control of cholera, measles, malaria, TB and HIV/AIDS (a detailed study of the life cycle of the malarial parasite is not required) (an appreciation of social and biological factors and how economic factors can affect these should be included); (e) discuss the factors that influence the global patterns of distribution of malaria, TB a

1 Tobacco smoke contains tar, carbon monoxide and  nicotine.  2 Tar settles on the epithelium lining the bronchi and  bronchioles and stimulates inflammation, an increase  in the secretion of mucus and an accumulation of  phagocytes from the blood.  3 Damage to the airways and alveoli occurs in chronic  obstructive pulmonary disease (COPD). In chronic  bronchitis, the airways are obstructed by mucus  and infection; in emphysema, alveoli are destroyed,  reducing the surface area for gas exchange.  4 Tar contains carcinogens, which cause changes in  DNA in bronchial epithelial cells, leading to the  development of a bronchial carcinoma. This is lung  cancer. 5 Some of the signs and symptoms of COPD are  breathlessness, wheezing and constant coughing;  two of the symptoms of lung cancer are coughing up  blood and chest pains.  6 Carbon monoxide combines irreversibly with  haemoglobin, reducing the oxygen-carrying capacity  of the blood.  7 Nicotine stimulates the nervous system, increasin