Untitled Flashcards Set

Understanding Disease

Photo Credit: Steve Gschmeissner/Science Source

Objectives

Identify what causes infectious diseases.

Explain how bacteria spread and cause disease.

Explain how eukaryotic pathogens spread and cause

disease.

Explain how viruses spread and cause disease.

Classifying Diseases

Infectious disease: when microorganisms disrupt normal

body functions

Pathogens: microorganisms that cause disease

-The mid-nineteenth century, French chemist Louis Pasteur and

German bacteriologist Robert Koch proposed that infectious diseases

occur when microorganisms disrupt normal body functions.

Microorganisms were commonly called “germs,” so this conclusion was

called the germ theory of disease.

Diseases can also be caused by toxic chemicals that may be

found in food or drinking water.

Bacterial Diseases

Some Human Bacterial Diseases

Disease

Effect on Body

Transmission

Lyme disease

“Bull’s-eye” rash at site of tick bite,

fever, fatigue, headache

Ticks transmit the bacterium Borrelia

burgdorferi.

Tetanus

Lockjaw, stiffness in neck and

abdomen, difficulty swallowing, fever,

elevated blood pressure, severe muscle

spasms

Bacteria enter the body through a break

in the skin.

Tuberculosis

Fatigue, weight loss, fever, night

sweats, chills, appetite loss, bloody

sputum from lungs

Bacteria particles are inhaled.

Bacterial

meningitis

High fever, headache, stiff neck,

nausea, fatigue

Bacteria are spread in respiratory droplets

caused by coughing and sneezing; close

or prolonged contact with someone

infected with meningitis

Strep throat

Fever, sore throat, headache, fatigue,

nausea

Bacteria are spread by coughing,

sneezing, or by direct contact with sores

or breaks in the skin infected by bacteria.

Bacterial Diseases – Vaccines

- Many bacterial diseases can be prevented by

stimulating the body’s immune system.

Vaccine: preparation of weakened or killed pathogens or

inactivated toxins

- Immunity is the body’s ability to destroy pathogens or

inactivated toxins.

- A number of drugs can be used to attack a bacterial

infection.

-Drugs that include antibiotics, such as penicillin and

tetracycline, block the growth and reproduction of

bacteria.

Bacterial Diseases – Control Methods

Most bacteria are harmless and many are beneficial, but the

everyday risk of a person acquiring a bacterial infection is

great enough to warrant efforts to control bacterial growth.

Control methods include:

Physical removal- Washing hands,

Disinfectants- Chemical solutions that kill bacteria

Food storage- Low temperatures slow the growth of bacteria

Food processing- Boiling, frying, steaming sterilizes

Sterilization by heat- has to be 100°C

Eukaryotic Pathogens

Fungi tend to thrive in warm, moist environments, and

those places include parts of the human body.

Athlete’s foot is caused by fungi that attack the skin,

often in the areas between the toes where moisture

may collect.

A single-celled fungus known as Candida can infect

tissue in the mouth, causing the condition known as

thrush.

Protists, sometimes called protozoa, can infect humans in

several ways and cause life-threatening diseases, such as

malaria.

Viruses

Viruses must infect living cells to grow and reproduce, taking

advantage of the nutrients and cellular machinery of their hosts. This

means that all viruses are parasites

Viruses have many of the characteristics of living things. After

infecting living cells, viruses can reproduce, regulate gene

expression, and even evolve.

Viruses

Viruses and Cells

Characteristic

Virus

Cell

Structure

DNA or RNA in capsid,

some with envelope

Cell membrane, cytoplasm; eukaryotes also

contain nucleus and many organelles

Reproduction

Only within a host cell

Independent cell division, either asexually

or sexually

Genetic Code

DNA or RNA

DNA

Growth and

Development

Yes; in multicellular organisms, cells

increase in number and differentiate

Obtain and Use

Energy

Yes

Response to

Environment

Yes

Change Over

Time

Yes

Viruses – cont.

A virus is similar to a computer virus.

Viruses – HIV Replication

HIV makes a DNA copy of

itself that inserts into the

host’s DNA. There, it may

remain inactive for many cell

cycles.

The deadly disease called acquired immune deficiency syndrome (AIDS) is caused

by an RNA virus called human immunodeficiency virus (HIV). HIV belongs to a

group of RNA viruses that are called retroviruses. The genetic information of a

retrovirus is copied from RNA to DNA instead of from DNA to RNA.

Much like a prophage in a bacterial host, the viral DNA may remain inactive for

many cell cycles before making new virus particles and damaging the cells of the

host’s immune system. Eventually, the DNA is transcribed and new viral parts are

made.

Once activated, the viruses leave the cell and begin to destroy the very system of

the body that would normally fight infection.

Viruses – COVID-19 Infection

The COVID-19 virus binds to a receptor on a cell membrane and gains

access to a cell. Once inside the cell, the virus uses the cell's machinery

to make new virus particles, which are released from cell.

Once activated, the viruses leave the cell

and begin to destroy the very system of the

body that would normally fight infection.

Then, the viral RNA is released from

vesicle.

Then the cell’s machinery is used to

translate the viral RNA into viral proteins.

Once the new viral proteins are made, the

new virus particle is released from the cell

and can infect other cells.

TEKS Checkpoint

What processes can cells do but viruses cannot do on their

own?

TEKS 5D

The Immune Response to Disease

Photo Credit: SPL/Science Source

Objectives

Explain the body’s nonspecific defenses against

pathogens.

Explain the function of the immune system’s specific

defenses.

Describe the health problems that may result when the

immune system does not function properly.

Describe the function of vaccines.

Nonspecific Defenses

1. In response to the

wound and invading

pathogens, white blood

cells called mast cells

release histamines, which

stimulate increased blood

flow to the area.

2. Local blood vessels

dilate. Fluid leaves the

capillaries and causes

swelling. White blood

cells called phagocytes

move into the tissue from

the blood.

3. Phagocytes engulf

and destroy the

bacteria and damaged

cells.

Specific Defenses: The Immune

System

Recognize “self”

and “nonself”

Antigens- any

foreign substance

that can stimulate a

immune response

Lymphocytes-main

working cells of

immune response

B cells and T cells

Humoral and

cell-mediated

immunity

Specific Defenses: The Immune

System – cont.

Humoral Immunity-

antibodies bind to

antigens in body fluids

and tag them for

destruction by other

parts of the immune

system.

Specific Defenses: The Immune

System – cont. 2

Cell-Mediated

Immunity-body cells that

contain antigens are

destroyed.

It begins when a

macrophage consumes a

virus and displays an

antigen on its surface.

Helper T cells bind to

macrophages and are

activated

Specific Defenses: The Immune

System – cont. 3

Secondary Response

- The role of memory cells is to remember that pathogen in case it infects the

body again.

- If the pathogen is encountered again, the secondary immune response is

triggered

- The response to the invasion of the same pathogen is quicker in the

secondary response than in the primary response.

Immune System Disorders

Sometimes the immune system overreacts to antigens or doesn’t react at

all. Problems with immune system function can result in:

Allergies – Allergens can trigger an immune response.

Asthma- a chronic disease in which air passages narrow

Autoimmune Disease- when the immune system attacks its own body

cells

Vaccines

The basic idea behind vaccination is to stimulate the

immune system to produce an immune response to a

disease without exposing an individual to that disease.

Vaccines work by taking advantage of antigens and

immunological memory.

When a person is vaccinated with these antigens, the

immune system generates antibody-producing cells.

If the person comes in contact with this antigen again, the

body is ready to fight.

TEKS Checkpoint

How does the circulatory system interact with the immune

system during the inflammatory response?

TEKS 12A

Emerging Diseases and Pandemics

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Objectives

Explain the impacts of emerging diseases.

Explain how COVID-19 emerged as a new disease.

Emerging Disease

COVID-19: A Continuing Challenge

Epidemic: an infectious disease that becomes widespread

in a particular population

Pandemic: an infectious disease that reaches epidemic

proportions in multiple countries throughout the world.

COVID-19 was an emerging disease and quickly became an

epidemic and then a pandemic, which a great recent

example of the two.

the vaccines prepared during the first year of the pandemic were targeted

toward the initial form of the COVID-19 virus. However, variants of the virus

began to appear within a few months and some of these variants were more

effective at evading the immune system and made the vaccines less effective.