Fever: Videos & Practice Problems

Fever, defined as a body temperature above 37.8°C, is a crucial innate immune response that helps eliminate pathogens. The hypothalamus regulates body temperature, and elevated temperatures inhibit bacterial growth while enhancing inflammatory responses through increased enzymatic activity. Pyrogens, which can be endogenous or exogenous, induce fever. Although fever can cause discomfort, it serves as a protective mechanism against infections, highlighting its role in the second line of defense in innate immunity.

Fever

Fever is an innate immune response characterized by an abnormally high body temperature, specifically above 37.8 degrees Celsius (100 degrees Fahrenheit). This physiological change is part of the body's second line of defense against infections, aimed at eliminating microbes. The hypothalamus, a region in the brain, acts as the body's temperature-regulating center, maintaining normal body temperature around 37 degrees Celsius (98 degrees Fahrenheit).

Elevated body temperatures associated with fever can inhibit the growth of most bacteria, serving as a protective mechanism against infections. Additionally, fever enhances the body's protective functions by increasing the rates of enzymatic reactions, which in turn boosts the inflammatory response and the release of inflammatory cytokines. These cytokines play a crucial role in fighting off pathogens more effectively during a fever.

The term pyrogens refers to substances that induce fever. They can be classified as endogenous pyrogens, produced within the body, or exogenous pyrogens, originating from external sources. Understanding the role of pyrogens is essential in recognizing how the body responds to infections.

In summary, while a fever may cause discomfort, it is a vital response that aids in the elimination of microbes and enhances the immune system's effectiveness. This innate effector action is a key component of the body's defense mechanisms, illustrating the complex interplay between temperature regulation and immune response.

Lipopolysaccharide (LPS) is an endotoxin created by some gram-negative (-) bacteria that commonly causes fever in humans. Lipopolysaccharide is what type of molecule?

• A. Endogenous pyrogen.
• B. Exogenous pyrogen.
• C. Pathogenic pyrogen.
• D. External pyrogen.

Answer: (B)

Fever can have positive effects on the process of fighting an infection. Which of these answers is not a positive effect fever can have during an infection?

• A. High body temperatures inhibiting the growth of many pathogenic bacteria.
• B. High body temperatures increase the enzymatic reactions associated with the immune system.
• C. High body temperatures enhance the inflammatory response and release of inflammatory signals.
• D. High body temperatures constrict the blood vessels ensuring the infection does not spread throughout the body.

Answer: (D)

Here’s what students ask on this topic:

What is the role of the hypothalamus in regulating body temperature during a fever?

The hypothalamus acts as the body's temperature-regulating center. During a fever, pyrogens (fever-inducing cytokines) signal the hypothalamus to raise the body's set point temperature above the normal 37°C. This elevated set point leads to an increase in body temperature, which helps inhibit bacterial growth and enhances the body's immune response. The higher temperature accelerates enzymatic reactions, boosting the inflammatory response and the release of cytokines, thereby aiding in the elimination of pathogens.

How do pyrogens induce fever?

Pyrogens are substances that induce fever by affecting the hypothalamus. They can be endogenous, produced within the body, or exogenous, originating outside the body. When pyrogens are released, they signal the hypothalamus to increase the body's set point temperature. This results in an elevated body temperature, or fever, which helps inhibit the growth of bacteria and enhances the immune response by speeding up enzymatic reactions and promoting the release of inflammatory cytokines.

Why is fever considered a part of the innate immune response?

Fever is considered part of the innate immune response because it is a non-specific defense mechanism that the body uses to fight off infections. When the body detects the presence of pathogens, pyrogens are released, signaling the hypothalamus to raise the body temperature. This elevated temperature inhibits bacterial growth and enhances the immune response by increasing the rate of enzymatic reactions and promoting the release of inflammatory cytokines. These actions help the body eliminate the pathogens more effectively.

What are the benefits of fever in fighting infections?

Fever offers several benefits in fighting infections. Elevated body temperatures inhibit the growth of many bacteria, making it harder for them to survive and multiply. Additionally, higher temperatures enhance the body's immune response by accelerating enzymatic reactions, which in turn boosts the inflammatory response and the release of cytokines. These processes help the body to more effectively eliminate pathogens. Although fever can cause discomfort, it serves as a protective mechanism to aid in the rapid clearance of infections.

What is the difference between endogenous and exogenous pyrogens?

Endogenous pyrogens are fever-inducing substances produced within the body, typically by immune cells in response to infection or inflammation. Examples include cytokines like interleukin-1 (IL-1) and tumor necrosis factor (TNF). Exogenous pyrogens, on the other hand, originate outside the body and are often components of pathogens, such as lipopolysaccharides (LPS) from bacterial cell walls. Both types of pyrogens signal the hypothalamus to raise the body's set point temperature, resulting in fever.