Unit 3: Diversity of Life
Module 3: Bacteria, Viruses, and Disease
Learning Objectives: Numerous objectives are covered in this lesson.
Lesson 2: Disease Fighters
Lesson Objectives:
- To outline the human body’s methods of guarding against and fighting off disease causing agents.
- To gain an understanding of the problems caused by the misuse of antibiotics.
Evaluation:
- Activity: “The Challenge of Antibiotic Resistance” (reading and questions)
The human body is designed to guard against and fight off foreign invaders, especially those which are disease causing.
To begin with the body is equipped with a number of mechanisms that help prevent foreign invaders from entering. These mechanisms are often referred to as mechanical or first line of defence. The first line of defence includes the following:
i) Skin
Our skin is an important defence mechanism. Covering almost every surface of our body, it does a good job at keeping many invaders out of our body. (Just think of how easily a minor infection can develop when this barrier is broken with something as small as a paper cut.)
i) Mucous
This lovely substance that lines the nose and throat has ability to trap invaders and prevent them from entering and interfering with the functions of our bodies.
ii) Tears
Our tears contain special enzymes that are capable of destroying bacteria.
iii) Stomach pH
You are probably well aware of the fact that the contents of your stomach are quite acidic. Stomach acids play an important role in helping to break down some of the harmful invaders that reach your digestive system. (Many bacteria enter our body with the foods that we eat in a normal day.)
As with any system, the body’s first line of defence is not one hundred percent efficient. If the first line of defence fails and harmful foreign invaders are allowed to enter the body, the body’s second line of defence will attempt to take control of the situation. In this process, many specialized cells, including white blood cells, are involved with destroying and engulfing foreign invaders.
Cellular defence methods are not always capable of taking control of the situation. The body’s third line of defence, also known as the humeral response, helps take control of the situation through the production of antibodies. The body produces specially designed antibodies in response to specific foreign invaders. Antibodies cause foreign invaders to clump together so that they can be more easily destroyed and engulfed.
You are likely familiar with the notion that a person who has had the chicken pox or the mumps is far less likely to get these conditions a second time. Once antibodies have been produced to fight off a particular pathogen the antibodies stay in a person’s system. If the person comes into contact with the same virus again, their body recognizes the invaders, and the pathogen will likely be destroyed before the person shows any symptoms of the disease.
For further information on the body’s immune response please refer to the following textbook reading:
“Immune Response” p.174-180 Nelson Biology
The modes of defense described above are considered to be natural immunity. Of course, scientific advancement has allowed for the use of techniques such as vaccinations and antibiotics, which assist the body’s fight against pathogens.
The following link will take you to an article that appeared in the March 1998 publication of Scientific American. The article describes how the continued overuse of antibiotics has lead to a problem known as antibiotic resistance.
“The Challenge of Antibiotic Resistance”
"The Challenge of Antibiotic Resistance"- Questions:
- What are antibodies? Explain how they harm bacteria.
- What does it mean when bacteria are resistant to antibiotic?
- Using scientific names identify some of the types of bacteria that have become or are becoming antibiotic disease.
- Explain how some bacteria are actually capable of helping our bodies protect against disease.
- What are “antibiotic susceptible types” of bacteria?
- When should antibiotics not be prescribed for an infection?
- What are the two main factors that lead to antibiotic resistance?
- Explain how antibiotic “resistance genes” prevent antibiotics from doing their job.
- Which bacterial cells are first affected when a person begins an antibiotic prescription? Which bacterial cells usually remain unaffected?
- Do antibiotics attack only harmful bacteria? Explain your answer.
- Explain what the author means when he refers to antibiotics as “societal drugs”.
- Besides the over-prescription of antibiotics, what other actions would be considered misuse?
- Other than for human medication, where else are antibiotics used?
- What can the general public do to help reverse the resistance problem?
- What can physicians do to help reverse the resistance problem?
