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Questions and Answers
Which of the following is an example of a communicable infectious disease?
Which of the following is an example of a communicable infectious disease?
Noninfectious diseases can be caused by infectious agents.
Noninfectious diseases can be caused by infectious agents.
False (B)
What is the role of normal microflora in the human body?
What is the role of normal microflora in the human body?
Competition for space and nutrients, and antagonism using bacteriocins.
An __________ is an after effect that remains after recovery from a disease.
An __________ is an after effect that remains after recovery from a disease.
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Match the types of infectious diseases with their descriptions:
Match the types of infectious diseases with their descriptions:
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What do transferrins in the blood bind to?
What do transferrins in the blood bind to?
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Bacteriocins are substances produced by bacteria to inhibit the growth of other bacteria.
Bacteriocins are substances produced by bacteria to inhibit the growth of other bacteria.
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What is the main characteristic of a chronic infectious disease?
What is the main characteristic of a chronic infectious disease?
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What characterizes a local infection?
What characterizes a local infection?
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A primary infection can be followed directly by another primary infection.
A primary infection can be followed directly by another primary infection.
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What is the term for an infection that produces few or no symptoms?
What is the term for an infection that produces few or no symptoms?
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The ________ phase is characterized by the presence of initial symptoms after the incubation period.
The ________ phase is characterized by the presence of initial symptoms after the incubation period.
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Which of the following is an example of a systemic infection?
Which of the following is an example of a systemic infection?
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Match the following terms with their definitions:
Match the following terms with their definitions:
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What is the role of sebum on the skin?
What is the role of sebum on the skin?
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Superinfections can only occur in the presence of primary infections.
Superinfections can only occur in the presence of primary infections.
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The ________ phase of infectious disease is when the illness reaches its highest intensity.
The ________ phase of infectious disease is when the illness reaches its highest intensity.
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Specific host defences respond immediately when an invader is detected.
Specific host defences respond immediately when an invader is detected.
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What is immunological memory?
What is immunological memory?
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The skin serves as a __________ barrier to infection.
The skin serves as a __________ barrier to infection.
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Match the following immune responses with their characteristics:
Match the following immune responses with their characteristics:
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Which of the following is NOT a movement that helps in flushing out potential pathogens?
Which of the following is NOT a movement that helps in flushing out potential pathogens?
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Cilia in the respiratory tract act to trap and expel pathogens.
Cilia in the respiratory tract act to trap and expel pathogens.
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What is the purpose of flushing actions like urine and tears?
What is the purpose of flushing actions like urine and tears?
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Study Notes
Host Microbe Interactions
- Host-microbe interactions are complex relationships between organisms.
- The immune system protects against infection.
Why Don't We Get Sick All the Time?
- The immune system defends against infections.
Host Defenses
- The immune system uses innate and adaptive immunity to combat pathogens.
Innate Immunity
- First line of defense
- Includes physical and physiological barriers (skin, mucous membranes, cilia, body temperature, pH).
- Non-specific defenses.
- Cells like neutrophils, macrophages, dendritic cells and natural killer cells are involved.
Adaptive Immunity
- Second line of defense
- Specific host defenses
- Includes cells like T helper cells, cytotoxic T cells, naïve B cells, and plasma cells.
- Develops antibodies (memory) to fight specific pathogens that have been encountered before.
Factors leading to Illness
- Clostridium tetani produces exotoxin that causes tetanus.
- A puncture wound from a dirty nail can introduce this bacterium, which in turn produces the toxin.
Outcomes of Host Defenses
- Immune responses involve the body reacting to pathogens and infections.
- Different outcomes are possible—no apparent illness, illness that resolves, and intervention.
Host Defenses - How Do They Work?
- The body's immune system combats different infections based on the immune response.
Overview of Non-Specific Host Defenses
- Innate defenses lack specificity and act rapidly.
- Example: skin and mucous membranes provide a physical barrier.
- Adaptive defenses respond to specific invaders and take longer to work.
- Possess "memory" to respond to previous encounters more effectively (faster and greater magnitude of response).
Physical (Anatomical Defenses)
- Skin: Physical barrier preventing infection entry.
- Mucous Membranes: Physical defenses lining respiratory, digestive, and urogenital systems; mucous traps bacteria, preventing attachment.
- Flushing: Urine, sweat, tears, and saliva wash pathogens away.
- Respiratory Tract: Cilia, coughing, and sneezing remove pathogens.
Biochemical Defense Tactics
- Skin: Low pH, high salt, sebum (fatty acids), and lysozyme (enzyme) inhibit pathogen growth and cause bacterial lysis.
- Gastrointestinal Tract: Gastric acid (low pH) inhibits pathogen growth. Transferrins (iron-binding proteins) limit pathogen availability.
Normal Microflora
- Normal microflora (microorganisms normally present) exist in various body locations.
- They compete for resources (space, nutrients), preventing pathogen colonization.
- Produce bacteriocins (toxic proteins).
Specific Immunity & Antibodies
- Antibodies bind to pathogens, preventing infection by blocking receptor binding or stimulating phagocytosis.
Infectious Disease Terminology
- Differentiates between infectious and non-infectious illnesses.
- Infectious diseases are caused by infectious agents.
- Non-infectious diseases are caused by other factors besides infections.
Communicable vs. Noncommunicable Infections
- Communicable infections spread from one host to another. Contagious infections spread easily between hosts (ex. chickenpox).
- Noncommunicable infections use alternate routes to spread, such as ingestion (botulism).
Signs, Symptoms, and Sequelae
- Signs: Observable disease characteristics (rash, swelling).
- Symptoms: Felt characteristics of a disease (pain, nausea).
- Sequelae: Long-term aftereffects of disease (permanent damage after an infection).
Types of Infectious Diseases
- Acute: Rapid onset (colds).
- Chronic: Long-lasting (tuberculosis).
- Subacute: Intermediate between acute and chronic.
- Latent: Periods of dormancy before and between active disease phases (herpes simplex virus).
Types of Infections
- Local: Limited to a specific area (boil, bladder infection).
- Systemic: Throughout the body via the bloodstream or other systems (measles, typhoid fever).
Primary and Secondary Infections
- Primary infection: Initial infection.
- Secondary infection: Occurs due to a weakened immune system after a primary infection (or another infection). Opportunistic infections are secondary infections.
Stages of Infectious Diseases
- Including incubation, prodromal, and acme phases, as well as convalescent and decline periods.
- Stages vary among different pathogens.
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Description
Test your knowledge on the intricate relationships between hosts and microbes. Explore how the immune system functions to protect against infections and the roles of both innate and adaptive immunity. Understand the factors leading to illness and how specific cells contribute to defense mechanisms.