Reminder: this unit is about maintaining homeostasis in the human body! homeostasis: a stable, internal environment

You want to be like this on the inside… Even if the outside world is like this…

One of the main ways to disturb homeostasis is illness! Did you know: Researchers from the Wright Patterson Medical Center in Dayton, Ohio, asked people standing in line at a grocery store checkout and at a high school concession stand to trade a $1 bill from their pocket for a new one. Then the doctors analyzed 68 of those old, worn bills. 87% of these bills contained harmful bacteria that could cause illness!

By the end of today you will be able to answer the questions: Why am I not always sick if I come in contact with bacteria that often? What does my body do when I do get sick?

Pathogens A disease causing bacteria, virus, parasite, or fungus

THE FIRST LINE OF DEFENSE Key Point #1: Your body tries to stop pathogens before they cause infection THE FIRST LINE OF DEFENSE The skin: very few pathogens can get through the layers of dead cells on the skin’s surface Mucous membranes: trap pathogens with mucous Stomach acid: kills bacteria in food

BUT- what if the pathogen gets past your first line of defense and breaks into your body???

Your immune system saves the day! Key point# 2: The function of the immune system is to fight infection from pathogens

Key Point #3: Your body’s second line of defense against infection is called the inflammatory response Fever Swelling Redness Heat

Key Point #4: If the body’s first and second lines of defense don’t work then the immune system must identify and kill the pathogen

Step 1- Investigate the problem Every pathogen has a different fingerprint called an antigen. B-cells bring antibodies that match the antigen. Antibody Antibody binding to antigen Germ

Step 2- Call for back-up! Antibodies signal the immune system to make white blood cells to come fight the disease

Step 3- Arrest the criminal!!! - “Eater” white blood cells- surround and “eat” bacteria and viruses, breaking them down and destroying them

Step 4- Put them in the system Memory b-cells: store information about the pathogen so that if it reappears again, antibodies will be immediately released (aka next time, step 1 will be MUCH faster)

Which of the following is a part of your body’s first line of defense against pathogens? White blood cells Red blood cells Skin Nervous system

A pathogen is… A) Pathway for white blood cells to follow to attack diseases B) A disease causing agent such as a virus or bacterial infection C) The best medicine for bacterial infections D) A cell that matches up to an antigen

Which of the following is not part of your body’s immune system Stomach White blood cells Skin antibodies

Which of the following is not part of your body’s first line of defense when fighting illness? Coughing Itching Swelling Fever

What part of your immune system can be compared to a SWAT team because it surrounds and destroys pathogens? a) Skin b) White blood cells c) b-cells d) antibodies

Memory B-cells… a) Help your body remember the part of your body that was last infected b) Show your body how to fight all infections with the help of your brain c) Form after the pathogen has been fought off to help form antibodies in the future d) Remember the type of white blood cell that needs to be used to fight a certain disease

Independent Practice

Different kinds of pathogens Two big ones: bacteria and viruses 1. Bacteria- hard to prevent, easy to get rid of (take antibiotics) 2. virus- some are easy to prevent (vaccine), impossible to get rid of- you will always have it!

Vaccine Vaccines contain weakened or dead versions of the antigens that cause diseases. They DO NOT make you sick. Vaccines DO get your body to produce the antibodies for the pathogen so if you do get sick, you can fight it off easily!