Problem 5 - Biology E/M

Question

Which of the following is true about histamine? (A) It is part of the body's first line of defense. (B) It kills germs by dissolving them. (C) It is a toxin released by microbes or germs. (D) It causes sneezing and a runny nose in an attempt to rid the body of germs. (E) It is part of the body's specific immune response.

Step-by-Step Solution

Answer

The correct answer is (D): Histamine causes sneezing and a runny nose.

Step 1: Understanding Histamine's Function

Histamine is a compound released by cells in response to injury and in allergic and inflammatory reactions, causing contraction of smooth muscle and dilation of capillaries.

Step 2: Identifying Histamine's Role in the Body

The primary role of histamine involves causing symptoms like sneezing and a runny nose, as the body attempts to expel irritants or allergens.

Step 3: Eliminating Incorrect Options

(A) Histamine is not part of the body's first line of defense but is involved later in inflammatory responses. (B) Histamine doesn't dissolve germs; it aids in expelling irritants. (C) It is not a toxin released by microbes. (E) Histamine is part of the non-specific immune response rather than specific.

Step 4: Selecting the Correct Option

After process of elimination and knowing the role of histamine, option (D) is correct: histamine causes sneezing and a runny nose to remove germs or irritants.

Key Concepts

Immune System

The immune system is the body's defense mechanism against germs and pathogens. It is comprised of various cells, tissues, and organs that work together to protect the body. This complex system can be divided into two main parts:

• Innate Immunity: This is the body's first line of defense and includes physical barriers like the skin and mucous membranes, as well as immune cells that target all pathogens indiscriminately.
• Adaptive Immunity: This involves a more specific response to pathogens. It includes lymphocytes, such as B cells and T cells, which adapt to the types of germs they encounter.

The immune system also features non-specific responses, such as inflammation, which can be activated by various triggers, including the release of histamine.

Inflammatory Response

The inflammatory response is an essential part of the immune system's reaction to injury or infection. It involves a series of steps aimed at eliminating harmful stimuli, like pathogens or injured cells, and begins the healing process. Here are the main features of inflammation:

• Histamine Release: Histamine is a key player in the inflammatory response. Released by mast cells, it causes blood vessels to expand and become more permeable. This allows more immune cells to enter the affected area.
• Redness and Swelling: These are common symptoms of inflammation. The increased blood flow causes redness, while increased fluid in tissues leads to swelling.
• Pain and Heat: Inflammatory chemicals stimulate nerves, causing pain. Additionally, the increased blood flow can raise the temperature in the affected area, which is another hallmark of inflammation.

In sum, the inflammatory response helps bring immune defenses to the site of infection or injury, facilitating the attack on invaders and cleaning up dead cells.

Allergic Reactions

Allergic reactions occur when the immune system overreacts to a substance that is usually harmless, known as an allergen. This overreaction can trigger symptoms that range from mild to severe. Histamine is one of the major compounds released during these reactions. Here's a closer look at allergic responses:

• Common Allergens: These include pollen, dust, pet dander, insect stings, and certain foods.
• Histamine's Role: When an allergen is detected by the immune system, cells release histamine. Histamine causes symptoms such as sneezing, watery eyes, and a runny nose, as the body attempts to eliminate the allergen.
• Managing Allergies: Antihistamines are common medications used to treat allergic symptoms by blocking the action of histamine.

While allergic reactions can be uncomfortable and disruptive, understanding the role of histamine can help in managing symptoms effectively.