Ch. 43 Ap Biology

1. List the two lines of nonspecific defense mechanisms with examples of each.

•External defense, which includes the skin and mucous membranes in the body. •Internal defense which includes phagocytic cells and antimicrobial proteins.

2. What is meant by specific defense?

Defense mechanisms are said to be specific because depending on which one they focus on one specific part of the body or a specific type of pathogen.

3. Give examples of “barrier defense.”

An example of a barrier defense is the largest organ on the human body, the skin. This organ provides both physical and chemical barrier against the environment.

4. What is the role of phagocytic leukocytes?

the role of phagocytic leukocytes is to engulf invading microorganisms that have gone through the external defense.

5. What is the role of the lymphatic system?

The lymphatic system collects fluid that is lost by the blood and returns it back to the circulatory system.

6. How does the lymphatic system aid in immunity?

It stores defensive phagocytic cells that defend against substances that enter the lymph nodes.

7. Outline the significant steps that occur during an inflammatory response?

The significant steps in the inflammatory response are the release chemical signals, capillaries dilate, increases temperature.

8. What is an antigen?

A foreign substance that enters the body and alters the defenses in the body.

9. Identify several differences between the lymphocyctes.

a. B Lymphocytes: produced in the bone marrow and are part of the humoral response.

b. T Lymphocytes: mature in the thymus gland and are part of the cell mediated response.

10. What is the role of MHC?

The role of MHC is to be a surface marker to indicate to the helper T-cells if it is a foreign invader or self.

11. What is the role of cytotoxic T cells and describe their mechanism of action?

Cytotoxic T-cells destroy infected body cells in the body through the use of enzymes to cause a cell to later do apoptosis. These can destroy cancer cells.

12. What are some of the actions of helper T cells?

Helper T-cells recognize antigens, they stimulate B cells and Cytotoxic T cells to attack the antigens.

13. How do B cells become activated?

The surface immunoglotulin that serves as the B-Cell antigen receptor (BCR) has two roles in B-cell activation. First, like the antigen receptor on T cells, it transmits signals directly to the cell’s interior when it binds antigen. Second, the B-Cell antigen receptor delivers the antigen to intracellular sites where it is degraded and returned to the B-cell surface as peptides bound to MHC class II molecules.

14. When B cells are activated, what do they do?

The start dividing and multiplying and either become plasma cells which contain the antibodies, or the become memory B cells.

15. List and briefly describe four ways antibodies aid in immunity.

-Opsonins are antibodies that bind to antigens on the outer surface which enables phagocytes to recognize the microorganism and destroy it.

-Antitoxins bind to toxins produced by micoorganisms rendering them harmless to the body.

-Agglutinins are antibodies that bind to antigens, causing the microorganisms to clump together. Thus, microorganisms cannot enter the host cells to reproduce.

-Lysins are antibodies that bind to the antigens of a microorganism causing them to rupture or disintegrate.

16. Why is secondary response quicker and more robust than primary response?

Secondary response is quicker and more robust than primary response because in the secondary response the body has memory cells in the plasma that are activated when the second exposure of the antigen occurs.

17. Define active immunity.

This is immunity in an organism that’s a result from the production of antibodies or lymphocytes after an antigen is identified in the body.

18. Define passive immunity.

This is immunity that is acquired by the transfer of anitbodies from one individual to another. For example, from a mother to her offspring.

19. What happens when you have an allergy?

The body creates histamines to fight the toxin or irritant, called an allergen.

20. Propose a possible reason why there may be a small percentage of people who have a

natural immunity to HIV?

A possible reason is because HIV is a virus that targets the helper T cells and without the helper T cells there could be no acquired immunity that protects the body from foreign pathogens. Now, if the Helper T cells had a certain immunity to this virus like a variation in their CCR5 gene, then it might be possible that the virus could not infect all Helper T cells. Or it could be that this person has an abnormally heightened immune system that as soon as the first helper T cell gets infected it could be destroyed by a Cytotoxic T-cell.