Question 1

Mediators that induce their effect without entering the circulation are referred to as:&#10;A) hormones.&#10;B) neurotransmitters.&#10;C) autacoids.&#10;D) second messengers.

Accepted Answer

Autacoids are local hormones or signaling molecules that act on the same cell or nearby cells without entering the circulation. Examples of autacoids include prostaglandins, leukotrienes, histamine, and cytokines. Hormones and neurotransmitters can enter the circulation to affect distant target cells, while second messengers are intracellular molecules involved in signal transduction pathways.

Question 2

Which of the following mediators acts on a distant target?&#10;A) Neurotransmitter&#10;B) Classic hormone&#10;C) Local hormone&#10;D) Autacoid

Accepted Answer

Classic hormones can act on distant target cells because they are secreted into the bloodstream and can travel throughout the body to reach their target cells. Neurotransmitters and local hormones generally act locally on nearby cells, while autacoids can act locally or systemically but do not circulate in the bloodstream to act on distant targets.

Question 3

Which of the following mediators is released directly into the bloodstream?&#10;A) Hormones&#10;B) Neurotransmitters&#10;C) Autacoids&#10;D) None of the above

Accepted Answer

Hormones are released directly into the bloodstream from endocrine glands and can travel throughout the body, affecting multiple target organs or tissues. Neurotransmitters and autacoids are released locally and do not directly enter the bloodstream.

Deck 28: An Introduction to Chemical Mediators