Immune System

I. How Do Pathogens Cause Disease? A. Louis Pasteur discovered that disease came from microorganisms, living things to small to see without a microscope. B. Robert Koch’s studies showed that a microorganism that causes disease is better known as a pathogen and can only cause one type of infectious disease. Ex. What causes strep throat can’t cause chicken pox.

II. Types of Pathogens A. There are 5 major types of human pathogens: – 1. Viruses – 2. Bacteria – 3. Protists – 4. Fungi – 5. Parasites B. They all can be spread through contact with a sick person, other things, or an object in the environment. Infect & destroy healthy cells-making you sick Smallest

III. Body’s Defenses A. First line of defense: – 1. Skin – oils & chemicals kill pathogens – 2. Breathing Passages – lined with cilia that remove foreign particles (sneeze/cough) – 3. Mouth/Stomach – saliva & stomach acid kill pathogen that may be on your food.

IV. Inflammatory Response A. Second line of defense: Inflammatory response which is a general response regardless of the pathogen which includes: – 1. White Blood Cells – phagocytes, cells that engulf the pathogen & break them down – 2. Inflammation – capillaries widen increasing blood flow to area increasing white blood cell release (swelling) – 3. Fever – pathogens can’t grow in high temp.

FYI: Histamine is released any time the top layer of cells is irritated that’s why when you scratch your skin become red

V. Immune Response A. Third line of defense is the immune response which is controlled by the nervous system & can distinguish between different types of pathogens B. The white blood cells of this response are called lymphocytes, which are classified as either: – 1. T cells – recognize molecule markers known as antigens that mark pathogens – 2. B cells – produce proteins that destroy pathogens called antibodies, marking them for destruction

VI. Becoming Immune A. Immunity is the body’s ability to destroy pathogens before they can cause disease. B. Immunity can either be:

1. Active – when your immune system produces antibodies against a pathogen, acquired either by getting the disease or being vaccinated. It lasts for many years. a. Vaccine – harmless antigens are placed inside your body to produce memory T & B cells

2. Passive – immune system is given antibodies, only lasts within the body a short time period

VII. Fighting Infectious Disease A. Infectious diseases usually affect normal function of the respiratory, circulatory & digestive systems. B. Most commonly used to fight disease caused by bacteria are antibiotics. – 1. Antibiotics – a chemical that slows the growth or kills bacteria without harming human body cells C. Viruses are not alive so you can not kill a virus with medicine but can reduce your symptoms

IIX. Noninfectious Disease A. Some noninfectious diseases are inherited while others are caused by environmental factors. – 1. Ex. Cystic fibrosis, Allergies, Asthma, Diabetes & Cancer B. If you have a higher risk to getting one of these diseases you should keep in mind – 1. Healthy diet, no exposure to carcinogen (sun & smoke), early detection by doctors