Fever - Online Tutor, Practice Problems & Exam Prep

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

This video we're going to begin our lesson on fever. And so fever is an innate effector action or an innate immune response, and it is characterized by an abnormally high body temperature. Body temperatures that are above 37.8 degrees Celsius are referred to as a fever. And so once again this fever, this abnormally high body temperature above 37.8 degrees Celsius is part of the second line of defense in innate immunity. And so it is an innate effector action that is designed to help eliminate microbes. Now a region in the brain known as the hypothalamus is known as the body's temperature regulating center. And again, normal body temperature is right around 37 degrees Celsius. And once again, high body temperatures above 37.8 degrees Celsius are referred to as a fever. And these high body temperatures above 37.8 degrees Celsius can actually inhibit most bacteria from growing. And so that is a protective mechanism to help prevent and eliminate infections. Also these higher body temperatures above 37.8 degrees Celsius that are associated with fevers can also enhance protective functions of the body. For example, they can enhance the inflammatory response and enhance the release of inflammatory cytokines, which is all going to help eliminate the microbes even better in the presence of a fever. And so these enhanced protective functions of the body are really due to the increased rates of enzymatic reactions in the body's higher temperatures. And so higher temperatures will allow for enzymatic reactions to proceed at an even faster rate than they otherwise usually would. Now, the term pyrogens refers specifically to fever inducing cytokines. So these are going to be cytokines that are going to be released by cells that can induce fever. And so endogenous pyrogens are going to be made inside of the body, whereas exogenous pyrogens are made externally outside of the body. And so if we take a look at our image down below, notice on the left hand side, we have this little cartoon, and notice doctor Klutch over here says he's feeling great. Let's study microbiome because he has a normal body temperature and he does not have an infection. And so his body temperature is 37 degrees Celsius or about 98 degrees Fahrenheit, which is normal body temperature. Now notice over here on the right hand side, doctor Klutch has gotten some kind of bacterial infection. And so doctor Klutch now has a fever. And so notice that his body temperature is elevated and it is greater than 37 degrees Celsius which is greater than 98 degrees Fahrenheit. And so notice that he's not feeling so good. And so although fevers, you do not feel very well with a fever, it is good to know that the fever is really just a response that your body is generating to help eliminate the microbes faster. And so over here on the right hand side, we're showing you our map of the lesson on innate immunity. And once again here in this video we're talking about the second line of defense, specifically the innate effector actions, and we're specifically focusing on fever here in this lesson. And so this here concludes our brief introduction to fever. And we'll be able to get some practice applying these concepts as we move forward in our course. And so I'll see you all in our next video.

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.

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.

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.