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The adrenal medulla is a group of cells in the center of the adrenal gland that can secrete adrenaline and norepinephrine in response to stress. These hormones have various physiological effects, including increasing heart rate and metabolism. Overactivity of the adrenal medulla can cause adverse effects, while exercise-induced hormone release is considered beneficial.
The adrenal medulla is a mass of cells that make up the center of the adrenal gland under the outer adrenal cortex. These irregularly shaped cells are grouped together with blood vessels. The marrow cells are called chromaffin cells as they stain a brownish color in reaction to chromic salts. The adrenal medulla can secrete norepinephrine and epinephrine, also known as adrenaline, when stimulated. Traces of dopamine can also be released from the adrenal medulla.
Generally, the adrenal medulla is a sympathetic ganglion – excitable cells that are part of the sympathetic nervous system (SNS). The sympathetic nervous system activates adrenal medullary secretion when stress is present. This action is preparation for the body’s fight-or-flight response in times of stress, such as anticipated danger. The ratio of hormones released varies according to the species. A human releases about 80% adrenaline and 20% norepinephrine. In contrast, chickens release about 30% adrenaline and 70% norepinephrine.
Tyrosine is the amino acid responsible for converting proteins into adrenaline and norepinephrine in the adrenal medulla. Both hormones are released into the bloodstream in response to stress, heavy blood loss, or exercise. The effects last for a while and may not disappear immediately after stress levels drop or exercise is over. Adrenaline can also be released due to low blood glucose levels.
Adrenaline causes the breakdown of glycogen into glucose in the liver, widens the arteries in the body, and releases fatty acids from fatty tissue. Norepinephrine increases blood pressure and constricts blood vessels. The most obvious physiological effect is an increase in heart rate and adrenaline strength. The bronchioles in the lungs dilate to increase the intake and output of air. Metabolism increases, which increases the amount of calories and glucose consumed and results in more energy. The pupils dilate, the gastrointestinal system decreases in acidity, and noncritical motor activity is reduced.
Overactivity of the adrenal medulla in cancer can cause adverse effects, such as high blood pressure or headaches. The effects of hormones produced by the adrenal medulla after exercise are considered beneficial. On the other hand, the decrease in gastrointestinal acids causes indigestion, which is why it is not recommended to exercise less than an hour after eating.
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