This chapter discusses disease as homeostatic dysfunction and explores causes and types of human diseases, including both infectious diseases and noninfectious diseases. Special emphasis is given to sexually transmitted infections, HIV/AIDS, and cancer.
- 21.1: Case Study: Threats to Our Health
- Nineteen-year-old Lauren spent a relaxing week of summer vacation visiting her grandparents in New Jersey. She particularly enjoyed taking their dog on long walks in the woods near their home, occasionally spotting deer on the overgrown paths.
- 21.2: Homeostasis and Disease
- Imagine driving on this seemingly endless road. Hopefully, your imaginary car is equipped with cruise control. Cruise control can help keep you safe as well as help you avoid a speeding ticket by keeping the speed of the car at the speed limit. Cruise control works by monitoring the car’s speed and adjusting the throttle as needed to keep the speed within a narrow range around the set speed limit.
- 21.3: Infectious Diseases
- Her real name was Mary Mallon (1869-1938), but she was nicknamed “Typhoid Mary.” She gained notoriety (as evidenced by this newspaper article) by being the first person in the United States to be identified as an asymptomatic carrier of the pathogen that causes typhoid fever.
- 21.4: Sexually Transmitted Infections
- This artwork is entitled “Columbus and the Indian Maiden.” It was painted around 1875 by Constantino Brumidi, an Italian-American historical painter. It is a good image to represent the concept of Columbian exchange. This concept refers to the exchange of pathogens during initial contacts between Europeans and Native Americans, starting when Columbus arrived in the New World in 1492. One of those pathogens may have been the sexually transmitted bacterium that causes syphilis.
- 21.5: HIV and AIDS
- AIDS stands for acquired immunodeficiency syndrome. It is a disease caused by infection with the human immunodeficiency virus, or HIV. HIV is a sexually transmitted virus that infects and destroys helper T cells of the human immune system (see the concept Disorders of the Immune System to learn more about how HIV infects immune system cells). AIDS eventually develops in most people with untreated HIV infections, usually several years after the initial infection with the virus.
- 21.6: Noninfectious Diseases
- Noninfectious diseases include all diseases that are not caused by pathogens. Instead, noninfectious diseases are generally caused by genetic or environmental factors other than pathogens, such as toxic environmental exposures or unhealthy lifestyle choices. Most noninfectious diseases have a complex, multifactorial set of causes, often including a mix of genetic and environmental variables.
- 21.7: Cancer
- Cancer is actually a group of more than 100 diseases, all of which involve abnormal cell growth with the potential to invade or spread to other parts of the body. In general terms, cancer occurs when the cell cycle is no longer regulated due to DNA damage. The number of potential underlying causes of this DNA damage is great, so there are many different risk factors for cancer. Any cells that become cancerous divide more quickly than normal cells. They may form a mass of abnormal cells called a
Thumbnail: This colorized transmission electron microscopic (TEM) image revealed some of the ultrastructural morphology displayed by an Ebola virus virion. Image used with permission (Public Domain; Frederick A. Murphy via CDC).