neurohumorale

Neurohumoral signaling, also described as neurohormonal signaling, is the process by which neurons release chemical messengers into the bloodstream to influence distant target tissues. It represents a key interface between the nervous and endocrine systems, complementing fast synaptic neurotransmission with slower, body-wide regulatory effects. Neurosecretory cells, whose axons project into blood vessels or specialized capillary beds, are central to this system.

Mechanisms and examples illustrate its diversity. The hypothalamus produces releasing and inhibiting hormones that travel through the hypophyseal portal system to regulate anterior pituitary secretion. The posterior pituitary releases vasopressin (antidiuretic hormone) and oxytocin directly into the blood, although these hormones are synthesized in hypothalamic neurons. The adrenal medulla functions as a neuroendocrine organ: sympathetic neurons stimulate chromaffin cells to release epinephrine and norepinephrine into the circulation, producing widespread physiological effects. Beyond these classic pathways, many tissues release neuropeptides and peptide hormones in response to neural input, influencing metabolism, fluid balance, reproduction, stress responses, and behavior.

Physiological roles of neurohumoral signaling include regulating cardiovascular function, maintaining fluid and electrolyte homeostasis, coordinating growth and metabolism, and modulating the endocrine system itself. Dysfunctions in neurohumoral pathways can contribute to disorders such as hypertension, diabetes, pituitary diseases, and stress-related illnesses. Ongoing research continues to elucidate the diverse networks by which neural activity translates into hormonal signals that coordinate organism-wide physiology.