What triggers the release of epinephrine and norepinephrine?

Answer: Epinephrine (adrenaline) and Norepineprine (noradrenaline) are hormones released during the fight-or-flight response of the sympathetic division of the autonomic nervous system.

The major physiologic triggers of epinephrine and norepinephrine release are stresses, such as physical threat, excitement, noise, bright lights, and high or low ambient temperature.

Explanation:

The nervous system can be divided into two functional parts: the somatic nervous system and the autonomic nervous system. The somatic nervous system causes contraction of skeletal muscles (voluntary actions). The autonomic nervous system controls cardiac and smooth muscle, as well as glandular tissue (involuntary actions). The autonomic nervous system regulates many of the internal organs through a balance of two aspects, or divisions. The two divisions of the autonomic nervous system are the sympathetic division and the parasympathetic division.

Adrenaline/epinephrine is released in response to the activation of the sympathetic nervous system. It increases heart rate and heart contractility, constricts blood vessels, is a bronchodilator that dilates the bronchi of the lungs to increase air volume in the lungs, and stimulates gluconeogenesis.

The general function of norepinephrine is to mobilize the brain and body for action. Norepinephrine release is lowest during sleep, rises during wakefulness, and reaches much higher levels during situations of stress or danger (fight-or-flight response).