The Immune System & Disease

Homeostasis The need for organisms to maintain a controlled internal environment while the external environment is changing, maintaining a dynamic equilibrium

Homeostasis Organisms allow changes within definite limits to occur. Changes outside normal limits disrupt homeostasis producing illness, disease and possibly death

Factors That Cause Disease Inheritance: Defective genetic traits can be passed from parents to offspring Microorganisms: Bacteria or viruses can be often passed from one person to another indifferent ways (Infectious Diseases) some are more easily transmitted than others Pathogen: Disease causing agents

Factors That Cause Disease cont… Pollutants: Chemical agents present in the environment may upset the body’s normal functioning and produce disease. These pollutants include asbestos, lead, mercury, phosphorans, PCB’s (polychlorinated biphenyls) Organ Malfunction: A disease may develop when one or more of the bodies organs malfunctions

Factors cont… Harmful Lifestyles: Tobacco use, alcohol & drugs can disrupt homeostasis, producing illness. Overeating, unsafe sexual experiences and excessive stress can also lead to certain diseases

The Body’s Defenses Against Disease We are surrounded by microorganisms trying to get into us They can enter through the nose, mouth, cuts in the skin & the food that we eat

First Line of Defense NONSPECFIC (1st) “fortress walls” SPECIFIC (2nd) “security guards”

Nonspecific Line of Defense Your first line of defense against infection Keeps out any microorganisms The skin is the main physical barrier for our body, it protects the body from invaders as long as it is undamaged Fluids are released at certain places on the body to keep out microorganisms (EX: mucus in the respiratory tract, saliva in the mouth, tears in eyes, acid in stomach= all contain substances that can kill microorganisms)

Non Specific cont… Second line of defense Breaks (cuts) in the skin (inflammation) respond to infection. Phagocytic cells (special white blood cells) surround and engulf microorganisms, destroying them by ingesting them

Specific Defenses: An Immune Response Antigen- A protein on a foreign object that stimulates the immune system to produce antibodies Antibodies- Proteins that help destroy pathogens Antibodies bind to specific antigens

B & T Cells B Cells: B cells respond to certain antigens. The body contains many different types of B cells and each produce antibodies for one specific antigen Plasma Cells: specialized B cells that release antibodies into the blood stream to attack the pathogen that is causing the infection T Cells: (T Lymphocytes) regulate the activation of plasma cells Killer T cells can attack antigen-bearing cells directly. These are the most effective attacking cells in the immune system Antibodies are only in the “fluid” not inside the cell. T Cells/Killer T Cells (cytotoxic) punch holes in the membranes of infected cells. Helper T cells send out signals

Immune System cont… Vaccination- An injection that prepares the immune system to better fight a specific disease in the future

Active & Passive Immunity Active Immunity: Occurs when the immune system remembers previously encountered microorganisms and is better prepared to fight them later. Immunity produced by a vaccine Passive Immunity: A person is injected with a large quantity of antibodies to a particular antigen. These antibodies protect the body from a disease only for as long as the antibodies remain in the body