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YOUR BODYS DEFENSESChapter 27 Section 2

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OBJECTIVES:

Describe how your body keeps out pathogens

Explain how the immune system fights

infections

Describe 4 challenges to the immune system

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FIRST LINES OF DEFENSE:

Eyes/Mouth: special enzymes destroypathogens

Nose/Stomach: mucus carries pathogensaway

Skin: outer cells are dead and flake off;

glands secrete oil (chemicals kill pathogens)

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FAILURE OF FIRST LINES:

What if skin gets cut? Blood flow to injured area increases

Platelets seal the wound

Cells of the immune system are activated

Immune System: the cells and tissues thatrecognize and attack foreign substances in the body

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CELLS OF THE IMMUNE SYSTEM:

3 Main kinds of cells:Macrophages:

engulf and digest microorganisms that enter thebody

T Cells Coordinate the immune system and attackinfected cells

B Cells Immune system cells that make antibodies

Antibodies: proteins that attach tospecific antigens

Antigens: substances that stimulate animmune response

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RESPONDING TO A VIRUS:

1. Two paths: some virus particles are engulfed bymacrophages others infect body cells; viruses haveviral antigens

2. Two responses: helper T cells have receptor proteins

that recognize viral antigens; they begin aT cellresponse or a B cell response

3. T Cell Response: helper T cells activate killer T cells

4. Destroying Infected Cells: Killer T cells recognize theantigens on infected cells. Killer T cells destroy them.

5. B Cell Response: Helper T cells activate B cells whichthen make antibodies

6. Destroying Viruses: antibodies bind to antigens onviruses; clumped viruses are marked for destruction.

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IMMUNE RESPONSE:

http://www.biologycorner.com/resources/immune_response.gif

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FEVERS:

When macrophages activate helper T cellsthey send a chemical signal that tells yourbrain to turn up the heat!

A moderate fever (102F or 39C) slows thegrowth of some pathogens

Best temperature for T & B cells to multiplyfaster

Temp too high (104-106F) can be dangerous

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MEMORY CELLS:

Your immune system responds better to a secondexposure than the 1st

1st encounter: B cells make antibodies against a

pathogens antigens takes about 2 weeks not fastenough so you get sick

Some of the B cells become memory B cells theyremember how to make an antibody for a specific

antigen

2nd encounter: memory B cells can make antibodies in3-4 days

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CHALLENGES TO THE IMMUNESYSTEM:

The immune system is not perfect

In some conditions the immune system does

not work properly

Such asAllergies

Autoimmune DiseasesCancer

AIDS

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ALLERGIES:

Sometimes the immune system overreacts toantigens that are not dangerous

Allergy: an inappropriate reaction to food,medicine, pollen, dust

Symptoms: itchy eyes, asthma, sneezing

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AUTOIMMUNE DISEASES:

When the immune system attacks the bodysown cells

Immune system cells mistake the bodyscells for pathogens

Examples:

Rheumatoid Arthritis Type 1 Diabetes

Multiple Sclerosis (MS)

Lupus

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CANCER:

Healthy cells divide at a regulated rate

Tumors develop when cells divide at an

uncontrolled rate

If cancers invade the circulatory or lymphaticsystems, they can be spread to other parts of

the body

Treatments: Surgery, radiation, drugtherapies

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AIDS:

Human Immunodeficiency Virus (HIV) causesAcquired Immunodeficiency Syndrome (AIDS)

HIV infects the immune system

Helper T cells are destroyed

People with AIDS usually die from otherdiseases they cannot fight off