What hormone is released by the sympathetic system?

What hormone is released by the sympathetic system?

• A. Norepinephrine
• B. Acetylcholine
• C. Dopamine
• D. Serotonin

Answer: (A)

Norepinephrine is the main messenger used by the sympathetic system to affect target organs. When the sympathetic nervous system activates, postganglionic neurons release norepinephrine onto adrenergic receptors, producing effects like increased heart rate, pupil dilation, and bronchodilation. In the adrenal medulla, sympathetic signals also trigger the release of epinephrine (adrenaline) into the bloodstream, where it acts as a hormone to coordinate a body-wide response, with norepinephrine still contributing as well. The other substances listed aren’t the primary mediators of sympathetic activity: acetylcholine is used by preganglionic fibers (and by parasympathetic postganglionic fibers), while dopamine and serotonin are mainly CNS neurotransmitters and not the typical sympathetic effector agents.

Norepinephrine is the main messenger used by the sympathetic system to affect target organs. When the sympathetic nervous system activates, postganglionic neurons release norepinephrine onto adrenergic receptors, producing effects like increased heart rate, pupil dilation, and bronchodilation. In the adrenal medulla, sympathetic signals also trigger the release of epinephrine (adrenaline) into the bloodstream, where it acts as a hormone to coordinate a body-wide response, with norepinephrine still contributing as well. The other substances listed aren’t the primary mediators of sympathetic activity: acetylcholine is used by preganglionic fibers (and by parasympathetic postganglionic fibers), while dopamine and serotonin are mainly CNS neurotransmitters and not the typical sympathetic effector agents.