Chapter 21 - Section 21.2 - Study Guide - Assess Your Learning Outcomes - Page 844: 13

The four cardinal signs of inflammation are redness, heat, swelling, and pain. Inflammation is a complex biological response that occurs when the body's immune system is activated to defend against harmful stimuli, such as pathogens, tissue damage, or irritants. Chemicals known as inflammatory mediators play a crucial role in initiating and coordinating the inflammatory response. Here are some key inflammatory mediators and their specific actions: 1. **Histamine:** - **Action:** Histamine is released by mast cells and basophils in response to injury or infection. It causes vasodilation (widening of blood vessels), leading to increased blood flow to the affected area. This contributes to the redness and heat associated with inflammation. - **Effect:** Increased blood flow delivers immune cells, oxygen, and nutrients to the site of inflammation, promoting healing and immune response. 2. **Prostaglandins:** - **Action:** Prostaglandins are lipid compounds that are produced at the site of inflammation. They sensitize pain receptors (nociceptors), leading to pain and contributing to the sensation of discomfort. - **Effect:** Pain serves as a protective mechanism that discourages further use or movement of the injured area, allowing it to heal. 3. **Cytokines:** - **Action:** Cytokines are signaling molecules released by various immune cells. They mediate communication between immune cells, coordinating the immune response. Examples include interleukins and tumor necrosis factor (TNF). - **Effect:** Cytokines attract immune cells to the site of inflammation, promote vasodilation and increased vascular permeability, and regulate immune cell activation and function. 4. **Leukotrienes:** - **Action:** Leukotrienes are lipid mediators produced by immune cells such as leukocytes and mast cells. They cause further vascular permeability, attracting immune cells and increasing the movement of fluid into the tissue. - **Effect:** Increased vascular permeability leads to fluid accumulation, resulting in swelling at the site of inflammation. 5. **Chemokines:** - **Action:** Chemokines are a subset of cytokines that specifically attract immune cells to the site of inflammation. - **Effect:** Chemokines help recruit immune cells, such as neutrophils and macrophages, to the site of infection or injury, enhancing the immune response. 6. **Complement Proteins:** - **Action:** Complement proteins are activated during inflammation and contribute to vasodilation, increased vascular permeability, and opsonization (enhanced phagocytosis of pathogens). - **Effect:** Complement activation helps recruit immune cells and promotes pathogen elimination through opsonization and the formation of the membrane attack complex (MAC). These chemicals work together to initiate and regulate the inflammatory response. While inflammation is a critical defense mechanism, chronic or excessive inflammation can lead to tissue damage and various health conditions. Therefore, the inflammatory response is tightly regulated by the body to promote healing and protect against harmful stimuli.

The four cardinal signs of inflammation are redness, heat, swelling, and pain. Inflammation is a complex biological response that occurs when the body's immune system is activated to defend against harmful stimuli, such as pathogens, tissue damage, or irritants. Chemicals known as inflammatory mediators play a crucial role in initiating and coordinating the inflammatory response. Here are some key inflammatory mediators and their specific actions: 1. **Histamine:** - **Action:** Histamine is released by mast cells and basophils in response to injury or infection. It causes vasodilation (widening of blood vessels), leading to increased blood flow to the affected area. This contributes to the redness and heat associated with inflammation. - **Effect:** Increased blood flow delivers immune cells, oxygen, and nutrients to the site of inflammation, promoting healing and immune response. 2. **Prostaglandins:** - **Action:** Prostaglandins are lipid compounds that are produced at the site of inflammation. They sensitize pain receptors (nociceptors), leading to pain and contributing to the sensation of discomfort. - **Effect:** Pain serves as a protective mechanism that discourages further use or movement of the injured area, allowing it to heal. 3. **Cytokines:** - **Action:** Cytokines are signaling molecules released by various immune cells. They mediate communication between immune cells, coordinating the immune response. Examples include interleukins and tumor necrosis factor (TNF). - **Effect:** Cytokines attract immune cells to the site of inflammation, promote vasodilation and increased vascular permeability, and regulate immune cell activation and function. 4. **Leukotrienes:** - **Action:** Leukotrienes are lipid mediators produced by immune cells such as leukocytes and mast cells. They cause further vascular permeability, attracting immune cells and increasing the movement of fluid into the tissue. - **Effect:** Increased vascular permeability leads to fluid accumulation, resulting in swelling at the site of inflammation. 5. **Chemokines:** - **Action:** Chemokines are a subset of cytokines that specifically attract immune cells to the site of inflammation. - **Effect:** Chemokines help recruit immune cells, such as neutrophils and macrophages, to the site of infection or injury, enhancing the immune response. 6. **Complement Proteins:** - **Action:** Complement proteins are activated during inflammation and contribute to vasodilation, increased vascular permeability, and opsonization (enhanced phagocytosis of pathogens). - **Effect:** Complement activation helps recruit immune cells and promotes pathogen elimination through opsonization and the formation of the membrane attack complex (MAC). These chemicals work together to initiate and regulate the inflammatory response. While inflammation is a critical defense mechanism, chronic or excessive inflammation can lead to tissue damage and various health conditions. Therefore, the inflammatory response is tightly regulated by the body to promote healing and protect against harmful stimuli.