The Body’s Line of Defence Chapter 11 Section 11.2

Blood pressure regulation Blood pressure is monitors by blood pressure receptors in your carotid and aortic arteries. High blood pressure- if detected it sends a signal to medulla oblongata. Sympathetic nervous system is decreased and parasympathetic is increased. The main result is that the arteries DILATE – VASODILATION which will decrease blood pressure The opposite happens with low blood pressure and the end result will be a constriction of the vessels- VASOCONTRICTION to increase the blood pressure

Interesting Video Show video: microscopic assassins http://www.youtube.com/watch?v=CeVtPDjJBPU

Terms Pathogen =Greek for “producer of suffering” Microscopic organism Enters body Can be dangerous

What do Pathogens Want With Us?!?!? Wants to reach inside of body as it is an IDEAL place for many pathogens to grow and reproduce

Body Has 3 Lines of Defense Against Pathogens Barriers to keep pathogens out. General (non-specific) defenses against many pathogens. Specific defenses against particular pathogens.

1st Line of Defense: Barrier The body has the following physical and chemical barriers. Eyelashes. Cilia in trachea – sweep away. Tears, mucous, saliva and sweat – lysozyme. - Enzyme that destroys the cell walls of bacteria. Skin - When intact it can’t usually be penetrated - Can also produce acidic secretions that make the pH too low for microbes or bacteria to grow

2nd Line: Non-Specific Defenses (General) Includes 3 types of WBC Macrophages Neutrophils Monocytes Inflammation Brings in defensive cells and speeds healing Fever Slows growth of bacteria; speeds up body defenses Occurs inside body Destroys invading organisms

2nd Line: Non-specific Macrophages Develop from monocytes Eat foreign bacteria (phagocytosis) Found all over body

3rd Lind of Defense: The Immune System Kicks in to assist the body’s 1st and 2nd lines of defense FUNCTION: the recognition and destruction of specific pathogens or foreign molecules 2 characteristics Is specific Has a memory

3rd Line: Specific Defenses Lymphocytes divided into 2 main groups (depending on where they mature – both form in bone marrow) T lymphocytes (aka T cells) Mature in thymus gland (T=T) B lymphocytes (aka B Cells) Mature in bone marrow (B=B) http://health.howstuffworks.com/adam-200095.htm

When an antigen is detected… T cells that have the receptors specific for that particular invader are stimulated to divide repeatedly Forms 2 lines of cells Effector cells – attack enemy; short life Memory cells – remember particular invaders and mount a rapid response if it should ever appear again; longer life

3rd Line: Two types of Specific Defense Antibody-mediated Immune Response Defend primarily against antigens that are free in the body fluids Warriors = B cells Weapons = antibodies Cell-mediated Immune Response Protect against body cells that have become infected with pathogens Warrior = T cell

First Steps in Immune Response Pathogen invades cell Macrophage engulfs pathogen Macrophage puts piece of pathogen (ANTIGEN) on surface This antigen on the surface is presented to a HELPER T CELL Macrophage then activates helper T Cell

HELPER T CELLS THEN ACTIVATE BOTH LINES OF DEFENSE TO FIGHT AGAINST THAT SPECIFIC ANTIGEN

Cell-Mediated Response Steps 6. Helper T cells stimulates the killer T cell (that is bound to antigen on macrophage) to begin dividing 7. T Cells divide into two separate populations - memory cytotoxic T cells - (killer) effector cytotoxic T cells

Cell-Mediated Response Steps 7 CONT…. Killer T cells cause the target cell to burst and die (drills holes) AND Memory T cells remain in body and mount a quick response if the invader is encountered again!

And now for the Antibody-Mediated Immune Response! First steps of the Immune response occur, resulting in an activated helper T cell Helper T cell activates B cell to begin dividing into plasma cells (effector B cells) and memory B cells Memory B cells remember attack so next attack with that pathogen is faster Plasma cells secrete antibodies specific for that antigen

Antibody-Mediated Immune Responses Plasma cells secrete antibodies that are specific for that antigen Weapons = Antibodies Y-shaped proteins that bind to specific antigen Can only bind to antigens that are free in body fluids or on the surface of a cell. Cannot bind to toxins within a cell Have SAME SHAPE as the antigen receptors IMMUNE SYSTEM VIDEO (4min)

http://www.youtube.com/watch?v=Hr7jjlZI6NA