Final answer:
Upon neural stimulation, the adrenal medulla secretes catecholamines, specifically epinephrine (adrenaline) and norepinephrine (noradrenaline), which are integral to the fight-or-flight response by elevating vital physiological processes such as heart rate, blood pressure, and energy mobilization.
Step-by-step explanation:
The adrenal medulla secretes epinephrine and norepinephrine, also known as adrenaline and noradrenaline, into the blood upon neural stimulation. These hormones are collectively referred to as catecholamines. They are synthesized from the amino acid tyrosine and are stored within chromaffin granules in the adrenal medulla. When a person experiences stress, fear, anger, exercises, or has low blood sugar levels (hypoglycemia), these hormones are released into the bloodstream. They play a crucial role in the body's fight-or-flight response by increasing heart rate, blood pressure, and blood glucose levels, as well as accelerating the breakdown of glucose in skeletal muscle and adipose tissue fats.
Epinephrine is the primary hormone of the adrenal medulla, accounting for 75 to 80 percent of its hormone secretions. The release of epinephrine and norepinephrine is stimulated by acetylcholine, which is released by preganglionic sympathetic fibers that innervate the adrenal medulla. This process is part of the body's mechanism to prepare for the fight-or-flight response, a reaction to stress orchestrated by the sympathetic nervous system, with impulses originating from the hypothalamus.