Topic 6 Human Physiology: 6.3 Defense Against Infectious Diseases

What is three reason that skin a good non-specific barrier?

1) Skin is tough.

2) Secretes acidic oils that prevent growth of most bacteria.

3) Outer layer (epidermis) is mostly dead cells preventing contact with live cells.

What are the 3 ways Mucus membranes in trachea, nose, urethra & vagina block non-specific pathogens?

1) Produce a sticky mucus that traps pathogens.

2) Some of these membranes cilia that help move trapped

pathogens up & out of trachea.

3) Cells that secrete mucus also secrete an enzyme (lysozyme) that chemically damage pathogens.

Phagocytes?

• Pathogens have entered the blood, phagocytes (a type of leukocyte) recognize whether the cell is “self” or “not self.”

• It is it determined self; it is left alone. However, if “not self”, it is engulfed by phagocytosis.

• These cells contain lysosomes to chemically digest what has been engulfed.

• This is called non-specific because the identity of the pathogen has not been established, therefore no-self.

What is a Antigen?

• any ‘non-self’ substance, commonly protein on pathogens that causes an antibody response.

• (Most pathogens have several different antigens on

  their surface and trigger the production of many.

  different types of antibodies.)

What is an Antibody?

Protein molecules that we produce in response to a specific type of antigen. (fight them)

Clonal Selection Cell Types

• What is the function of a plasma?

• Antibody secretion into plasma

Clonal Selection Cell Types

• What is the function of B memory?

• Rapid cloning into plasma cells when challenged by second.

  exposure to same antigen.

What is the production of Antibodies?

1) Macrophage engulfs antigen.

2) Antigen is presented on the membrane of the macrophage

Helper T-cells (Lymphocytes/ type of white blood cell) bind to

the antigen on the macrophage and are activated.

3) Activated Helper T-cells bind to and activate B-cells (Lymphocytes).

4) There may be multiple antigens and, therefore multiple B-cells

(Polyclonal Selection).

5) B-cells clone by mitosis into plasma cells and memory cells

6) Plasma cells produce antibodies specific to the antigen

7) Memory cells provide long-term immunity by responding with

antibodies stronger and faster if the antigen is present again

later.

What are the Antibiotic Effects?

• Antibiotics work to block certain metabolic pathways of prokaryotic (bacteria) cells.

  • inhibit protein synthesis or prevent a new cell wall from forming however, due to differences in cell types, have no effect on eukaryotic cells of humans.

• Viruses have no metabolic pathways, so they rely on host cells to carry-out processes.

  • may inhibit or prevent these processes will also affect host eukaryotic cells.

• antibiotic damage or kill prokaryotic cells, but do not have an effect om eukaryotic cell or the virus that may have infected them.

What is Florey & Chain?

• Developed Penicillin

  • Tested on only a few mice before using it on humans.

  The first humans were close to death when given the

  penicillin.

  • Only one test before risking use on humans but results were very clear however initial samples were very impure and could have had toxic substances in them.

  • Extensive animal testing followed by small doses in

    humans is necessary to determine effectiveness and

    side-effects so their practice would be considered.

    unsafe by today’s standards.

What is Blood Clotting?

a) Platelets release a group of proteins called clotting factors.

into the plasma.

b) Clotting factors turns the inactive enzyme Prothrombin

into the active form Thrombin.

c) Thrombin turns the soluble plasma protein Fibrinogen into

the insoluble fibrous form Fibrin.

d) Fibrin forms a net that binds together platelets and blood

cells to form a solid ‘plug’ or clot for the wound.

What is HIV?

Human Immunodeficiency Virus (HIV) attaches to lymphocytes and takes over their nucleic acid and protein synthesis.

(These cells die, communication stops, and antibodies are not produced. The individual can no longer fight off pathogens as efficiently.)

What are type of lymphocytes (Helper-T cells)

Are responsible for communicating which cells need to be cloned and begin antibody production.

Transmission of AIDS

• Hiv can result in AIDS ( Acquired lmmune Deficiency syndrome)

How is Aids transmitted?

• Transmitted through the transfer bodies fluid.

  • Through small cuts or tears and sexual intercourse.

  • Traces of blood on hypodermic needles.

  • Across the placenta or through cuts during childbirth.

  • Blood transfusions at one time were not tested for blood-borne diseases.