Norepinephrine is released by which components of the nervous system?

• A. Parasympathetic ganglia.
• B. Cerebellum.
• C. Pituitary.
• D. Adrenal medulla and sympathetic nerves.

Answer: (D)

Norepinephrine is released in the nervous system primarily by the sympathetic division and by the adrenal medulla. In the sympathetic pathway, postganglionic neurons release norepinephrine onto the target organs, producing effects like increased heart rate and vasoconstriction. The adrenal medulla, acting like a modified sympathetic ganglion, releases catecholamines into the bloodstream when stimulated by preganglionic sympathetic fibers, with norepinephrine contributing to the systemic adrenergic response. Parasympathetic ganglia release acetylcholine, not norepinephrine; the cerebellum and pituitary do not serve as sources of norepinephrine release for autonomic signaling.