Chapter 28 Section 1 What causes Infectious Diseases

Chapter 28 Section 1 What causes Infectious Diseases? Infectious Disease – a disease caused by organisms that enter and multiply within the human body

Causes of Infectious Diseases n Infectious diseases are caused by some kind of pathogen (Germ). n Pathogens are parasites – organisms that live in or on another organism

Bacteria n A single celled microorganism. n Bacteria enter the body and start to multiply. n Bacteria can be cured with medicine.

Viruses n Smallest known type of infectious agent n A virus enters body cells, reproduces itself, and kills the cell. n Cannot be killed with medicine

Rickettsias n Resemble bacteria, but reproduce like viruses. n Usually found in fleas, mice, ticks, and mites. n Infections caused by bites or feces

Protozoans n Single celled organisms that are larger than bacteria. n Most common in places with poor sanitation.

Fungi n Prefer dark damp environments. n Cause infections of the scalp, nails, or feet.

Spread of Infectious Diseases n People: Direct or Indirect n Animals n A contaminated object n The environment

Immune Response n The innate immune system- your inborn defenses. n The adaptive immune systemadapts to specific types of pathogens.

Nonspecific Resistance n Physical Barriers: Skin, Mucus Membranes, Cilia. n Chemical Barriers: Tears, saliva, digestive juices. n Body Cells: White blood cells. n Inflammatory Response: Increase blood flow.

Specific Resistance n. B Cells: Create antibodies. n T Cells: Aid the activity of the B Cells and kill abnormal cells in the body.