1. CHAPTER 40 THE IMMUNE SYSTEM AND DISEASE
40-1 Infectious Disease
• Some diseases are inherited and others are caused by materials in the environment (cigarette smoke)
• There are even more that are caused by agents such as bacteria, viruses, and fungi
• Disease-causing agents such as bacteria are known as pathogens and cause infectious diseases because they infect the body of the person who gets sick

2. Agents of Disease • The human body provides just the right environment for growth; the right temperature, a watery environment, and many nutrients • Many bacteria produce toxins which are poisons that produce illness by upsetting the body’s functions • Some organisms act as parasites and live off of their host taking needed nutrients from them

3. intestinal roundworms
tapeworm

4. How Diseases are Spread • Some infections are spread from one person to another by coughing, sneezing, or physical contact • Other infectious diseases are spread through contaminated food or water • There are others that are spread by infected animals • Animals that carry disease-causing organisms from person to person are called vectors

6. Fighting Infectious Disease • Drugs are often used in the prevention of disease the most important of which is antibiotics • Antibiotics kill bacteria without harming the cells of the infected person • Antibiotics have no effect on viruses but we now have some antiviral drugs that are quite effective by inhibiting the ability of the virus to multiply inside of cells

7. 40-2 THE IMMUNE SYSTEM
• The immune system is the body’s primary defense against pathogens • The body’s first line of defense is to keep pathogens out and this is the job of the skin • If pathogens get in through the mouth and nose, they get trapped in mucus • The second line of defense is the body’s inflammatory response which is important if pathogens do manage to get in • When this happens the area gets red, swollen, and pus forms where bacteria are being engulfed by white blood cells; sometimes this is accompanied by fever

9. • If pathogens manage to get past the first and second lines of defense then the body reacts with a series of specific defenses called the immune response • The substance that triggers this response is an antigen • The body responds by forming a specific antibody to the antigen which will destroy it

10. Developing Immunity • Once the body has been exposed to a pathogen, millions of memory cells remain behind which can respond by making antibodies if there is another exposure to the same pathogen • The response is stronger and quicker the second time • There are two types of immunity; active and passive • The immunity produced by a vaccination (deliberate exposure to the pathogen) is called active immunity because the individual has the ability to produce an immediate active response against the pathogen • Passive immunity is also called maternal immunity because it occurs when antibodies pass from mother to fetus through the placenta or to the infant from the mother’s milk • Passive immunity protects the child for only the first few months of life or longer if the child is breast-fed