In your scientific notebooks, answer these 3 questions

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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?

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.


  • 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

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