1. The Body’s Line of Defence
Chapter 11
Section 11.2

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

3. Interesting Video Show video: microscopic assassins

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

5. 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

7. 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.

8. 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

9. 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

10. 2nd Line: Non-specific Macrophages Develop from monocytes
Eat foreign bacteria (phagocytosis)
Found all over body

11. 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

12. 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)

13. 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

15. 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

16. 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

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

19. 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

21. 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!

22. 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

24. 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)