Sympathetic responses generally are widespread because __.
Group of answer choices
NE and epinephrine are secreted into the blood as part of the sympathetic response
preganglionic fibers are long
inactivation of ACh is fairly slow
preganglionic fibers are short
The Correct Answer and Explanation is:
Correct Answer:
NE and epinephrine are secreted into the blood as part of the sympathetic response
Explanation:
The sympathetic nervous system is one of the two main divisions of the autonomic nervous system (ANS), the other being the parasympathetic nervous system. The sympathetic division is responsible for the body’s “fight or flight” response, preparing the body for action in stressful or emergency situations.
One of the defining features of the sympathetic response is that its effects are widespread and long-lasting, especially when compared to the parasympathetic response, which tends to be more localized and brief. The key reason for this widespread effect is that norepinephrine (NE) and epinephrine (also called adrenaline) are released into the bloodstream by the adrenal medulla, a gland located on top of the kidneys.
When the sympathetic nervous system is activated, preganglionic neurons stimulate the chromaffin cells of the adrenal medulla, causing them to release NE and epinephrine directly into the blood. These chemicals function as hormones (rather than neurotransmitters) and travel throughout the body, affecting distant organs and tissues. As hormones in the bloodstream, they do not rely on direct nerve connections, which allows their effects to be systemic (body-wide) rather than limited to a specific area.
Other options in the question are incorrect for the following reasons:
- “Preganglionic fibers are long” – This is characteristic of the parasympathetic system, not the sympathetic.
- “Inactivation of ACh is fairly slow” – This refers to acetylcholine, mainly used in the parasympathetic system. ACh is rapidly broken down by acetylcholinesterase.
- “Preganglionic fibers are short” – This is true for the sympathetic system but does not explain the widespread effect.
Therefore, the correct and most comprehensive reason for the widespread effects of the sympathetic nervous system is the hormonal release of NE and epinephrine into the blood.