CK-12 Life Science
Page 57
State how noninfectious diseases can be prevented.
Check Your Understanding
What is an infectious disease?
Discuss the stages of the cell cycle.
Introduction
Not all diseases spread from person to person. A disease that does not spread from person to person is called a noninfectious disease. Examples are cancer and diabetes. These diseases may or may not be caused by pathogens.
Causes of Noninfectious Diseases
Most noninfectious diseases have more than one cause. The causes may include genes and an unhealthy lifestyle. Genes may increase the chances that people will have certain diseases. However, other factors may determine whether the diseases actually develop. For example, what people eat or whether they smoke may also play a role.
Several noninfectious diseases are discussed in other chapters. For example, heart disease is discussed in Cardiovascular System chapter. In this lesson, the focus is on cancer, diabetes, and diseases of the immune system.
Cancer
Cancer is a disease in which abnormal cells divide out of control. Normally, the body has safeguards that prevent abnormal cells from dividing. In cancer, these safeguards fail.
What Causes Cancer?
Cancer is usually caused by mutations. From the Cell Division, Reproduction, and DNA chapter, you know that mutations are random errors in genes. Mutations that lead to cancer (usually multiple mutations in the same cell) usually occur in genes that control the cell cycle. Due to the mutations, abnormal cells divide uncontrollably. This often leads to a tumor. A tumor is a mass of abnormal tissue. As a tumor grows, it may harm normal tissues around it.
Anything that can cause cancer is called a carcinogen. Carcinogens may be pathogens, chemicals, or radiation. Figure 1 gives examples of carcinogens of each type.
Causes of Cancer
Pathogens
Pathogens that cause cancer include the human papilloma virus (HPV) and the hepatitis B virus. HPV is spread through sexual contact. It can cause cancer of the reproductive system in females. The hepatitis B virus is spread through sexual contact or contact with blood containing the virus. It can cause cancer of the liver (Figures below and below).
Figure 21.9
The mutations that cause cancer may occur when people are exposed to pathogens, chemicals, or radiation. Some common causes of cancer are shown here.
Figure 21.10
The mutations that cause cancer may occur when people are exposed to pathogens, chemicals, or radiation. Some common causes of cancer are shown here.
Chemicals
Many different chemical substances cause cancer. Dozens of chemicals in tobacco smoke, including nicotine, have been shown to cause cancer. In fact, tobacco smoke is one of the main sources of chemical carcinogens. Smoking tobacco increases the risk of cancer of the lung, mouth, throat, and bladder. Using smokeless tobacco can also cause cancer.
Radiation
Forms of radiation that cause cancer include ultraviolet (UV) radiation and radon. UV radiation is part of sunlight. It is the leading cause of skin cancer. Radon is a natural radioactive gas that seeps into buildings from the ground. It can cause lung cancer (Figure below).
Figure 21.11
The mutations that cause cancer may occur when people are exposed to pathogens, chemicals, or radiation. Some common causes of cancer are shown here.
Sometimes cancer cells break away from a tumor. If they enter the bloodstream, they are carried throughout the body. Then, the cells may start growing in other tissues. This is usually how cancer spreads from one part of the body to another. Once this happens, cancer is very hard to control.
Common Types of Cancer
Cancer occurs mainly in adults, especially in adults over age 50, as more mutations accumulate in cells over time. The most common type of cancer in adult males is cancer of the prostate gland. The prostate gland is part of the male reproductive system. Prostate cancer makes up about one third of all cancers in men. The most common type of cancer in adult females is breast cancer. It makes up about one third of all cancers in women. In both men and women, lung cancer is the second most common type of cancer. Most cases of lung cancer occur in smokers.
Cancer can also occur in children. However, childhood cancer is rare. Leukemia is the main type of cancer in children. It makes up about one third of all childhood cancers. It occurs when the body makes abnormal white blood cells.
Treating Cancer
If leukemia is treated early, it usually can be cured. In fact, many cancers can be cured if treated early. Treatment of cancer often involves removing a tumor with surgery. This may be followed by other types of treatments. These may include drugs and radiation, which kill cancer cells.
The sooner cancer is treated, the greater the chances of a cure. This is why it is important to know the warning signs of cancer. Having warning signs does not mean that you have cancer. However, you should see a doctor to be sure.
Everyone should know the warning signs of cancer. Detecting and treating cancer early can often lead to a cure.
Warning Signs of Cancer
Change in bowel or bladder habits
Sore that doesn’t heal
Unusual bleeding or discharge
Lump in the breast or elsewhere
Chronic indigestion
Difficulty swallowing
Obvious changes in a wart or mole
Persistent cough or hoarseness
(Source: http://www.uihealthcare.com/topics/cancer/canc4280.html, Courtesy: University of Iowa Hospitals and Clinics)
Diabetes
Another noninfectious disease is diabetes. Diabetes is a disease in which the pancreas cannot make enough insulin. From the Controlling the Body chapter, you know that insulin is a hormone that helps cells take up sugar from the blood. Without enough insulin, the blood contains too much sugar. This can damage blood vessels and other cells throughout the body. The kidneys work hard to filter out and excrete some of the excess sugar. This leads to frequent urination and excessive thirst.
Doctor Rosalyn Yalow is an American scientist that played a major role in our knowledge of diabetes. She helped discover a way to measure tiny amounts of insulin in the blood. She won a Nobel Prize for her discovery in 1977.
There are two main type of diabetes: type 1 diabetes and type 2 diabetes. Type 1 diabetes makes up about 5 to 10 percent of all cases of diabetes in the United States. Type 2 diabetes accounts for most of the other cases. Both types of diabetes are more likely in people that have certain genes. Therefore, having a family member with diabetes increases the risk of developing the disease. Either type of diabetes can increase the chances of having other health problems, as well. For example, people with diabetes are more likely to develop heart disease and kidney disease. Type 1 and type 2 diabetes are similar in these ways. However, the two types of diabetes have different causes.
Type 1 Diabetes
Type 1 diabetes occurs when the immune system attacks normal cells of the pancreas. As a result, the pancreas can no longer produce insulin. Something in the environment triggers the immune system to attack the pancreas. Scientists think that the trigger may be a virus. Type 1 diabetes usually develops in childhood or adolescence.
People with type 1 diabetes must frequently check the sugar in their blood. They use a meter like the one shown in Figure below. Whenever their blood sugar starts to get too high, they need a shot of insulin. The insulin brings their blood sugar back to normal. There is no cure for type 1 diabetes. Therefore, insulin shots must be continued for life. Most people with this type of diabetes learn how to give themselves insulin shots.
Figure 21.12
This is one type of meter used by people with diabetes to measure their blood sugar. Modern meters like this one need only a drop of blood and take less than a minute to use.
Type 2 Diabetes
Type 2 diabetes occurs when body cells no longer respond to insulin. The pancreas may still produce insuli
n, but the cells of the body cannot use it. Being overweight and having high blood pressure increase the chances of developing this type of diabetes. Type 2 diabetes usually develops in adulthood. However, it is becoming more common in teens and children. This is because more young people are overweight now than ever before.
Some cases of type 2 diabetes can be cured with weight loss. However, most people with the disease need to take medicine to control their blood sugar. Regular exercise and balanced eating also help. Like people with type 1 diabetes, people with type 2 diabetes must frequently check their blood sugar.
Diseases of the Immune System
The immune system usually protects you from pathogens and other causes of disease. In Lesson 4, you will read more about how the immune system works. When the immune system is working properly, it keeps you from getting sick. However, the immune system is like any other system of the body. It can break down or develop diseases. In the last lesson you read about AIDS. AIDS is an infectious disease of the immune system caused by a virus. Some diseases of the immune system are noninfectious. They include autoimmune diseases and allergies.
Autoimmune Diseases
An autoimmune disease occurs when the immune system attacks the body’s own cells. One example is type 1 diabetes. In this disease, the immune system attacks cells of the pancreas. Other examples are multiple sclerosis and rheumatoid arthritis. In multiple sclerosis, the immune system attacks nerve cells. This causes weakness and pain. In rheumatoid arthritis, the immune system attacks the cells of joints. This causes joint damage and pain. These diseases cannot be cured. However, they can be helped with medicines that weaken the immune system’s attack on normal cells.
Allergies
An allergy occurs when the immune system attacks a harmless foreign substance. A substance that triggers an allergy is called an allergen. It is the response of the immune system, not the allergen, which causes the symptoms of an allergy.
Did you ever hear of hay fever? It’s not really a fever at all. It’s an allergy to plant pollens. People with this type of allergy have symptoms such as watery eyes, sneezing, and a runny nose. A common cause of hay fever is the pollen of ragweed. A ragweed plant is shown in Figure below.
Figure 21.13
Ragweed is a common roadside weed found throughout the United States. Many people are allergic to its pollen.
Many people are allergic to poison ivy. A poison ivy plant is shown in Figure below. Skin contact with poison ivy leads to an itchy rash in people that are allergic to the plant.
Figure 21.14
Poison ivy plants are wild vines with leaves in groups of three. They grow in wooded areas in most of the United States. Contact with poison ivy may cause a rash in a person allergic to the plant.
As you have read, some people are allergic to certain foods. Nuts and shellfish are common causes of food allergies. Other common causes of allergies include:
drugs such as penicillin
mold
dust
dog and cat dander (dead skin cells)
stings of wasps and bees
To learn more about allergies and their causes, go to http://www.aafa_al.healthology.com/ allergies/focusarea.htm. You can watch a video about allergies at this Web site.
Most allergies can be treated with medicines. Medicines used to treat allergies include antihistamines and corticosteroids. These medicines help control the immune system’s response. Sometimes, allergies cause severe symptoms. For example, they may cause the throat to swell so it is hard to breathe. Severe allergies may be life threatening. They require emergency medical care.
Preventing Noninfectious Diseases
Most allergies can be prevented by avoiding the substances that cause them. For example, you can avoid pollens by staying indoors as much as possible. You can learn to recognize plants like poison ivy and not touch them. A good way to remember how to avoid poison ivy is “Leaves of three, let it be.” Some people receive allergy shots to help prevent allergic reactions. The shots contain tiny amounts of allergens. After many months or years of shots, the immune system gets used to the allergens and no longer responds to them.
Type 1 diabetes and other autoimmune diseases cannot be prevented. However, choosing a healthy lifestyle can help prevent type 2 diabetes. Getting plenty of exercise, avoiding high-fat foods, and staying at a healthy weight can reduce the risk of developing this type of diabetes. This is especially important for people that have family members with the disease.
Making these healthy lifestyle choices can also help prevent some types of cancer. In addition, you can reduce the risk of cancer by avoiding carcinogens. For example, you can reduce your risk of lung cancer by not smoking. You can reduce your risk of skin cancer by using sunscreen. How to choose a sunscreen that offers the most protection is explained in Figure below.
Figure 21.15
When you choose a sunscreen, select one with an SPF of 30 or higher. Also, choose a sunscreen that protects against both UVB and UVA radiation.
Some people think that tanning beds are a safe way to get a tan. This is a myth. Tanning beds expose the skin to UV radiation. Any exposure to UV radiation increases in the risk of skin cancer. It doesn’t matter whether the radiation comes from tanning lamps or the sun.
Lesson Summary
Causes of noninfectious diseases may include genes and an unhealthy lifestyle.
Cancer is caused by mutations and treated with surgery, drugs, and radiation.
Diabetes is a disease in which the pancreas cannot make enough insulin or use the insulin properly.
Autoimmune diseases occur when the immune system attacks normal body cells.
Allergies occur when the immune system attacks harmless foreign substances.
A healthy lifestyle can help reduce your risk of developing many noninfectious diseases.
Review Questions
What is a noninfectious disease?
List three carcinogens.
What other health problems are more likely in people with diabetes?
What causes rheumatoid arthritis?
How can you reduce your risk of developing skin cancer?
Explain how mutations can lead to cancer.
Why are frequent urination and excessive thirst symptoms of diabetes?
Compare and contrast type 1 and type 2 diabetes.
Some allergies occur during certain seasons, while others occur year-round. Give examples of allergens that you would expect to cause each type of allergy.
Why is maintaining a healthy weight especially important for people that have family members with type 2 diabetes?
Further Reading / Supplemental Links
Amy M. Mareck. Fighting for My Life: Growing up with Cancer. Fairview Press, 2005.
Jillian Powell. Allergies. Cherrytree Books, 2008.
Marlene Targ Birll. Diabetes. Twenty-First Century Books, 2007.
http://www.cancerindex.org/ccw/guide2c.htm http://www.cancer.gov/cancertopics/understandingcancer/immunesystem; http://www.cancerindex.org/ccw/guide2c.htm
http://www.mayoclinic.com/health/allergy/AA99999 http://www.cdc.gov/cancer/az/; http://www.mayoclinic.com/health/allergy/AA99999
http://www.4women.gov/FAQ/autoimmune.htm http://www.uihealthcare.com/topics/cancer/canc4280.html; http://www.4women.gov/FAQ/autoimmune.htm
http://en.wikipedia.org/wiki
Vocabulary
allergen
A substance that triggers an allergy.
allergy
A condition that occurs when the immune system attacks a harmless foreign substance.
autoimmune disease
A disease that occurs when the immune system attacks the body’s own cells.
cancer
A disease in which abnormal cells divide out of control.
carcinogen
Anything that can cause cancer.
diabetes
A disease in which the pancreas cannot make enough insulin.
noninfectious disease
Disease that does not spread from person to person.
tumor
A mass of abnormal tissue.
type 1 diabetes
The type of diabetes that occurs when the immune system attacks normal cells of the pancreas.
type 2 diabetes
Type of diabetes that occurs when body cells no longer respond to insulin.
Points to Consider
How do you think the body fights diseases like colds?
How do you think the immune system protects you from pathogens and other causes of disease?
Lesson 21.3: First Two Lines of Defense
Lesson Objectives
Describe your body’s first line of defense against pathogens.
Explain how inflammation helps protect you from pathogens.
Check Your Understanding
What are some of the functions of your skin?
What is a pathogen? Give some examples.
Introduction
Your body has many ways to protect you from pathogens. Your body’s defenses are like a castle of old. The outside of a castle was protected by a moat and high walls. Inside the castle, soldiers were ready to fight off any enemies that made it across the moat and over the walls. Like a castle, your body has a series of defenses. Only pathogens that get through all the defenses can harm you.