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Disease

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What is a disease?

Any state of existence in which one’s health is disrupted.

It’s hard to come up with an exact definition. Why?

… a look through any medical dictionary soon shows that articulating a satisfactory definition of disease is surprisingly difficult. And it is not much help defining disease as the opposite of health, given that definitions of health are equally tricky….
Why is it important to know what a disease or disability is?
One reason is practical: because today’s medicine has an unprecedented ability to actually do things, it matters a great deal what we decide to tackle. The ability to make powerful, effective interventions into people’s health brings with it new ethical responsibilities.

What is a disease? Jackie Leach Scully. EMBO Reports 2004 Jul; 5(7): 650–653

Causes of disease

Inherited disorders:

Mutated gene

Mutated chromosome

Incorrect # of chromosomes

Pathogens

Bacteria, fungi, viruses, protists

Parasitic infection

Very small animals

Exposure to toxins

Lead, cadmium, arsenic, etc.

Poor nutrition

Lack of exercise

Drug abuse

Exposure to ionizing radiation

Non-ionizing radiation, like visible light, or cell phone radiation, isn’t known to cause disease.

Vitamin or mineral deficiency

What are pathogens?

Any microscopic particles that reproduce in your body and cause disease.

The main categories are:

Pathogens

from ck12.org/book/CK-12-Biology-Concepts

How do we fight pathogens?

Use the right tool for the job

For each category below, we have drugs for some types, but not all.

Even when we do have a drug they are not always guaranteed to work.

antibiotics – Only kill bacteria. How antibiotics work

anti-virals – Only kill viruses.

These are not vaccines. Anti-virals are only given after you are infected.

anti-fungals – Only kill fungi.

anti-protozoal – Only kill protists.

anti-helminthic – Only kill parasitic worms (helminths)

Rarely needed for people in the United States. More commonly prescribed by veterinarians if one’s pet has worms.

viral vaccines – Can prime our immune system to help protect us against certain viruses

These are not anti-virals. Viral vaccines must be given before you are infected.

bacterial vaccines – Can prime our immune system to help protect us against certain bacteria.

These are not antibiotics. Bacterial vaccines must be given before you are infected.

Cancer

Cancers: Not one disease, but a family of diseases.

Auto-immune disorders

See our article on autoimmune diseases.

Mental illness as a disease

Psychiatry

Mysterious link between immune system and mental illness

Addiction is not a disease: A neuroscientist argues that it’s time to change our minds on the roots of substance abuse

Cognitive dissonance: When mental illness-like symptoms are not a disease.

Protein folding diseases

Prions! Protein folding diseases

Defenses against disease

Fighting pathogens

Lines of defense: Skin is our first barrier to disease

Immune system; White blood cells, antibodies, Killer T Cells.

Bacteria evolves resistance to antibiotics

 

Honors topics

High blood pressure, and a question: Are we consuming too little salt?

Impact of European plagues on Native Americans, and Americapox: The Missing Plague

Lack of exercise is a major cause of chronic diseases

Detecting genetic disorders with 3d face scans

Probiotics and human health

Mysterious link between immune system and mental illness

Skin is a barrier to disease

Our skin is the first step in our defense system.

Image 1: Skin is ruptured. Pathogens enter & endanger our body.

Image 2: Red blood cells are attracted to the cut (which will cause redness and swelling)

Image 3: Platelets and fibrins create a blood clot, sealing the wound. Marcophages (WBCs) come in and begin attacking pathogens.

Image 4: Other WBCs come in and start phagocytosis (surrounding and eating the pathogens, like Pac-Man eats dots.)

Pin skin histamines inflammatory_response

Pearson Education

Ecology: Our body as environment for disease

Pathogens can infect us and live on/in our body.

Our body become’s the pathogen’s ecosystem.

Germs on skin

The study of an organism in it’s ecosystem is called ecology.

It is important to note that not all bacteria is bad for us. The right variety of bacterial colonization in our gut (intestinal tract) is important for human health.

Probiotics and human health

 

So let’s look at the ecology of a person infected with bacteria:

Let’s say that a person is infected with a bacteria, S. epidermidis

Doctors discover that if you have a population of this bacteria on you, then it decreases the population of other types of bacteria on you.

a. Describe one way that decreasing the population sizes of other bacteria on the skin could help the S. epidermidis population.

b. Identify the process that S. epidermidis cells use to reproduce.

c. Describe two similarities between the process that skin cells use for cell division and the process that you identified in part (b).

When S. epidermidis moves from the skin into the body, it behaves like an invasive species entering a new ecosystem.

d. Will the S. epidermidis population size decrease, increase, or stay the same after the bacteria enter the body?

Using your knowledge of invasive species, explain your answer

Mental illness

Psychiatry is a medical field devoted to the diagnosis, study, and treatment of mental disorders.  Psychiatry

Addictions

Many psychologists claim that drug and alcohol addictions are a disease. However, many scientists disagree. In this article  A neuroscientist argues that it’s time to change our minds on the roots of substance abuse.

Honors Biology topics

How does our immune system target invaders?

Cancers: Not one disease, but a family of diseases.

Bacteria evolves resistance to antibiotics

High blood pressure, and a question: Are we consuming too little salt?

Impact of European plagues on Native Americans, and Americapox: The Missing Plague

Addiction is not a disease: A neuroscientist argues that it’s time to change our minds on the roots of substance abuse

Lack of exercise is a major cause of chronic diseases

Detecting genetic disorders with 3d face scans

Probiotics and human health

The immune system’s mysterious connection to mental health

Learning Standards

College Board Standards for College Success: Science

LSH-PE.5.4.3 Give examples, using evidence gathered from print and electronic resources, of genetic diseases (e.g., cystic fibrosis, sickle cell anemia, Tay-Sachs disease or phenylketonuria) that result from mutations to a single gene. Identify, for each example, the specific type of mutation that causes the change in amino acid sequence and ultimately the change in the protein that is produced.

LSH-PE.5.4.4 Give examples, using evidence gathered from print and electronic resources, of instances when viruses are linked to cancer. Explain, based on knowledge of viral gene insertions and of the relationship among DNA, proteins and traits, how a viral insertion into DNA can cause cancer.

LSH-PE.5.4.5 Give examples, using evidence gathered from print and electronic resources, of the potential of using viruses for curing genetic diseases via gene therapy. Make a claim about, and justify, based on knowledge of viral DNA and viral insertions, why some viruses are appropriate for this application.

Massachusetts Comprehensive Health Curriculum Framework

Students will gain the knowledge and skills to select a diet that supports health and reduces the risk of illness and future chronic diseases. PreK–12 Standard 4

Through the study of Prevention students will

8.1 Describe how the body fights germs and disease naturally and with medicines and immunization.

Through the study of Signs, Causes, and Treatment students will

8.2 Identify the common symptoms of illness and recognize that being responsible for individual health means alerting caretakers to any symptoms of illness

8.5 Identify ways individuals can reduce risk factors related to communicable and chronic diseases

8.6 Describe the importance of early detection in preventing the progression of disease. Through the study of Signs, Causes, and Treatment students will

8.7 Explain the need to follow prescribed health care procedures given by parents and health care providers

8.8 Describe how to demonstrate safe care and concern toward ill and disabled persons in the family, school, and community

8.13 Explain how the immune system functions to prevent and combat disease

Benchmarks for Science Literacy, AAAS

The immune system functions to protect against microscopic organisms and foreign substances that enter from outside the body and against some cancer cells that arise within. 6C/H1*

Some allergic reactions are caused by the body’s immune responses to usually harmless environmental substances. Sometimes the immune system may attack some of the body’s own cells. 6E/H1

Some viral diseases, such as AIDS, destroy critical cells of the immune system, leaving the body unable to deal with multiple infection agents and cancerous cells. 6E/H4

Vaccines induce the body to build immunity to a disease without actually causing the disease itself. 6E/M7** (BSL)

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