Midterm 1- Lesson 1-5

Question 1

Four ways in which microbes are transmitted to people

Answer 1

1. direct transmission
2. indirect transmission
3. biological transmission
4. mechanical transmission

Question 2

direct transmission

Answer 2

Involves bodily contact, such as handshaking, kissing, and sexual intercourse. For example, genital herpes is generally contracted by direct transmission.

Question 3

indirect transmission

Answer 3

This kind occurs when microbes are passed to an individual via airborne particles, dust water, soil, or food. Influenza is an example of environmentally transmitted disease.

Question 4

biological transmission

Answer 4

Biological transmission occurs when a transmitting agent, such as a mosquito, picks up microbes, changes them into a form conducive to growth in the human body, and passes on the disease to the human. The transmission of yellow fever, for example, occurs by this method.

Question 5

mechanical transmission

Answer 5

This is the passage of a microbe to an individual by means of a carrier that is not directly involved in the disease process. Transmission of an infection by dirty hands, bad water, rats, mice, or flies are methods of mechanical transmission. Although mechanical and biological transmission are similar in that an organism such as an insect can be a transmitting agent, mechanical transmission differs in that the microbe is carried on the surface of the transmitting agent (e.g., a fly) as opposed to inside of the agent (e.g., a mosquito).

Question 6

three factors that determine whether or not invading microbes will produce an infection

Answer 6

1. The number of organisms in the body.
2. The virulence of the organisms.
3. The body’s defensive powers against the microbes.

Question 7

four phases of an infection

Answer 7

1. Incubation period: between the time the infection is contracted and the time the symptoms appear.
2. Period of nonspecific symptoms: when symptoms such as headaches and general discomfort may appear, before the full onset of disease. During this time, the microbes are actively colonizing and producing toxins.
3. The acute phase: when the disease and its symptoms are at their height.
4. Unless the infection proves fatal, a period of decline follows the acute phase. During this period, the organisms are expelled from the mouth and nose in saliva and respiratory secretions, as well as through the digestive tract and the genitourinary system in feces and urine.

Question 8

three types of infections

Answer 8

1. Localized infections: which remain at their original site and do not spread to other parts of the body.
2. Focal infections: which are confined to a particular area, sending toxins to other parts of the body and causing other disruptions.
3. Systematic infections: which affect a number of areas of body systems.

Question 9

Distinguish between specific and nonspecific immune mechanisms.

Answer 9

Specific immunity is a defense mechanism that fights specific microorganisms and their toxins. It may be acquired by contracting a disease or through artificial means, such as vaccinations. There are two basic immunologic reactions: Humoral immunity and cell-mediated immunity (see below).
Nonspecific immunity: This is a set of general responses to any kind of infection or disorder. Nonspecific immunity is mediated in four main ways (see below).

Question 10

Describe the four main ways that nonspecific immunity is mediated

Answer 10

1. Anatomical barriers prevent the passage of microbes from one section of the body to another.
2. Phagocytosis is the process by which certain white blood cells (called phagocytes) ingest microbes. Phagocytes are usually overproduced when there is a bodily infection, so that sufficient numbers can be sent to the site of infection to ingest the foreign particles.
3. Antimicrobial substances are chemicals mobilized by the body to kill invading microorganisms.
4. The inflammatory response is a local reaction to infection. At the site of infection, blood capillaries enlarge and then a chemical agent called a histamine is released into the area. This serves to isolate the organism and to mobilize resources to the infected areas (such as blood).

Question 11

Distinguish between humoral and cell-mediated immunity

Answer 11

Humoral immunity is mediated by B lymphocytes (produced in bone marrow), which protect against bacteria, neutralizing toxins produced by bacteria, and preventing viral re-infection. B cells confer immunity by the production and secretion of antibodies, which are the basis of the antigen-specific reactions.
Cell-mediated immunity involves T lymphocytes (produced in thymus gland) and is a slower acting response. Rather than releasing antibodies into the blood, as humoral immunity does, cell-mediated immunity operates at the cellular level. When stimulated by the appropriate antigen, T cells secrete chemical agents that kill invading organisms and infected cells.

Question 12

Discuss the role of the spleen, tonsils and thymus gland in immunity

Answer 12

The spleen aids in the production of B cells and T cells and removes old red blood cells from the body. It also helps filter bacteria and is responsible for the storage and release of blood.
The tonsils are patches of lymphoid tissue in the pharynx that filter out microorganisms that enter the respiratory tract.
The thymus gland is responsible for helping T cells mature; it also produces a hormone, thymosin, which appears to stimulate T cells and lymph nodes to produce the plasma cells that, in turn, produce antibodies.

Question 13

Aids

Answer 13

an autoimmune disease, which is a progressive impairment of immunity. The immune system attacks its own body’s cells.

Question 14

cancer

Answer 14

now viewed—at least in part—as a compromise of the immune system, which would normally find and destroy cancer cells

Question 15

elephantitis

Answer 15

condition produced by worms that attack lymphatic tissue; it stems from blockage in the flow of lymph into the blood. Massive retention of fluid results, especially in the extremities

Question 16

Splenomegaly

Answer 16

is an enlargement of the spleen that may result from various infectious diseases. It hinders the spleen’s ability to produce phagocytes, antibodies, and lymphocytes.

Question 17

Tonsillitis

Answer 17

an inflammation of the tonsils that interferes with their ability to filter out bacteria.

Question 18

Infectious mononucleosis

Answer 18

viral disorder that can cause enlargement of the spleen and lymph nodes, as well as fever, sore throat, and general lack of energy.

Question 19

Lymphoma

Answer 19

is a tumor of the lymphatic tissue. Hodgkin’s disease, a malignant lymphoma, involves the progressive, chronic enlargement of the lymph nodes, spleen, and other lymphatic tissues. As a consequence, the nodes cannot effectively produce antibodies.

Question 20

immunity

Answer 20

The body’s resistance to injury from invading organisms, acquired from the mother at birth, through disease, or through vaccinations and inoculations

Question 21

specific immune mechanism

Answer 21

Responses designed to respond to specific invaders; includes cell-mediated and humoral immunity.

Question 22

nonspecific immune mechanism

Answer 22

A set of responses to infection or a disorder that is engaged by the presence of a biological invader

Question 23

phagocytosis

Answer 23

The process by which phagocytes ingest and attempt to eliminate a foreign invader.

Question 24

humoral immunity

Answer 24

A fast-acting immunologic reaction mediated by B lymphocytes that secret antibodies into the bloodstream; effective in defending against bacterial infections and viral infections that have not yet invaded the cells

Question 25

cell-mediated immunity

Answer 25

A slow-acting immunologic reaction involoving T lymphocytes from the thymus gland-effective in defending against viral infections that have invaded the cells, fungi, parasites, foreign tissues, and cancer.

Question 26

lymphatic system

Answer 26

The drainage system of the body; believed to be involved in immune functioning.

Question 27

autoimmunity

Answer 27

A condition in which the body produces an immune response against its own tissue constituents.