Essay: Avoiding Disruptions The Immune System p. 310

In your scientific notebooks, answer these 3 questions (we will return to these) How does your body know that a foreign cell is different? Why do antibiotics fail to help with the common cold? How does a vaccination against polio protect your for your whole life?

What is the function of the immune system? Protect your body from disruptions in homeostasis.

Uses 2 types of defenses Nonspecific barriers Specific immune responses

Nonspecific Barriers Barrier that does not have to recognize a particular invader.

Types of Nonspecific Barriers Skin: largest organ in body Bacteria: Millions of harmless bacteria live on the skin Macrophages: Made of cells in the blood that recognize & scavenge invading organisms & toxins

How are bacteria on skin beneficial? They keep disease-causing microorganisms called PATHOGENS, from living on the skin.

How do pathogens enter the body? Mouth, ears, eyes, nose, genital, urinary, & anal openings. Nonspecific defenses such as saliva, tears, cilia, hair, mucus & sweat secrete enzymes help to kill bacteria. Cuts on the skin, however, allow pathogens to bypass the skin’s nonspecific defenses.

Specific Immune Responses Respond to particular pathogens in the body. Macrophages alert helper T-cells to release molecules called Lymphokines. Lymphokines activate killer T cells which recognize & kill body cells infected with pathogens: Cell-Mediated Response

Bacteria vs. Virus Virus – immunization Bacteria – antibiotics

Antibody-mediated Response Specific immune defense. Macrophages activate cells called B cells which make antibodies. Antibodies are proteins that are carried by the bloodstream and attach to specific molecules called antigens.

How does an antibody recognize an antigen? Memory B cells memorize pathogens that your body has been subjected to in the past. Memory B cells make antibodies that specifically fight off these antigens.

Immunity? With this programmed response, your body may fight off the infection without ever having symptoms of the illness. Most people become immune to measles, mumps, or chicken pox after being infected once.

So, why do we still get sick? Pathogen escapes detection. Stressors weaken immune system Inadequate sleep Bad nutrition Drug use Smoking Depression Anxiety

Not all antigens are harmful Insect venom, pollen, animal dander & food. Immune system overreacts to these substances in people: ALLERGIES

What causes allergies? Body releases histamines which causes swelling, sneezing & itchiness. Medicine that counteracts histamines are called antihistamines.

Autoimmune Diseases Cause the immune system to mistake normal cells for pathogens. Body attacks healthy cells. Ex. RA & MS