Biology 12

132 MHR • Unit 2 Homeostasis

Chemotherapy and Homeostasis

Everyone begins life as a single cell. That cell

undergoes a series of divisions that ultimately

results in a human being. Just as important as cell

division in the formation of a human being is

differentiation, the process by which cells become

specialized in structure and function. They may

become white blood cells, muscle cells, or skin

cells, depending on their location and the body’s

stage of development.

We do not completely understand the system

that controls cell division and differentiation, but

researchers spend significant amounts of time and

money investigating these processes. The reason for

the high level of interest in this area of research is

that when the system goes wrong, the result can be

cancer. Cancer is uncontrolled cell division, and it

is the second-leading cause of death in Canada after

heart attacks. Knowledge of what controls cell

division and the processes that lead up to and

follow it may provide better methods of treating

or curing the disease.

At present, cancer is usually treated using surgery,

radiation, and/or chemotherapy. Chemotherapy is

the treatment of any disease using chemicals or

drugs, but the term is most commonly used to refer

to the treatment of cancers. Drugs that are used to

treat cancers attempt to interfere with the rapid

rates of growth and cell division of most cancer

cells. However, at present few of these drugs can

distinguish between cancer cells and normal body

cells. Some cells of the body, such as white blood

cells and cells lining the digestive tract, normally

reproduce rapidly. During chemotherapy these cells

are destroyed or damaged along with the cancerous

cells, resulting in the side effects, such as hair loss

and nausea, associated with this form of treatment.

Drugs used in chemotherapy can be divided into

three groups. The first group causes direct damage

to the DNA in the nucleus and the RNA of cells by

interfering with the processes associated with DNA

replication. The second group blocks the joining of

the nucleotides that make up molecules of DNA.

The third group prevents the formation of the

spindle fibres that control the movement of

chromosomes during cell division. Unfortunately,

all of these drugs affect normal, healthy cells while

attacking cancer cells. Researchers continue the

search for drugs that will target only the cancer

cells while leaving the healthy cells undamaged.

In this chapter, you saw how certain systems in

the body work in concert to maintain homeostatic

balance. In particular, you discovered how the

kidney, the pancreas, and the immune system use

negative feedback systems to control the body’s

internal equilibrium. In Chapter 5, you will see

how the nervous system functions as a key

component of homeostasis.

SECTION REVIEW

1. Describe the difference between an antibody
   and an antigen.


2. Describe how antibodies destroy antigens and
   the substances produced by antigens.


3. Draw a diagram that illustrates how harmful cells
   in the body are destroyed by macrophages.


4. Describe the difference between cellular
   immunity and antibody immunity.


5. List the types of immune cells formed in the
   bone marrow and describe their function.


6. Explain how memory T cells help provide
   immunity against future infections.


7. Is an allergic reaction to pollen a negative
   feedback loop or a positive feedback loop? Support
   your response.
   8. Make a chart that outlines advantages and
   disadvantages for specific immunity and non-specific
   immunity.
   9. Some early transplant patients experienced
   complications because their immune system
   responded to “invading” cells that originated in
   another body. Which immune system cells would
   increase? Draw a graph predicting how the
   concentration of different cells would change.

At present, organ transplant recipients must spend the

rest of their lives taking medications to suppress their

immune systems. As you are gathering information on

diabetes and treatments such as pancreatic cell

transplants, think about how immune responses would

complicate or limit the use of these medications.

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