What Is the Adrenal Medulla?

Adrenal medulla is the tissue that forms the center of the adrenal gland. Irregularly shaped cells line the wide vascular space, which also contains part of the reticuloendothelial system. Under the innervation of sympathetic nerves, it can secrete adrenaline. In this sense, the adrenal medulla is a neuroendocrine tra-nsducer that converts neural information into hormone information. The most important role of the adrenal medulla is thought to be to create the body's conditions to escape or prepare for struggle through sympathetic nerves in emergency situations. This is called the emergency doctrine of WBCannon (1928). Adrenal medulla chromaffin cells secrete epinephrine (E) and norepinephrine (NE) are both catecholamine hormones.

Adrenal medulla

Adrenal medulla is forming

Epinephrine is the main hormone of the adrenal medulla. Its biosynthesis is mainly the formation of norepinephrine in medulla chromium cells, and then further phenylethanolamine N-methyl transferase (PNMT). The effect of methylation of norepinephrine to form epinephrine.

The synthesis of medullary hormone is basically the same as the process of noradrenaline synthesis after the sympathetic ganglia.

The adrenal medulla is located in the center of the adrenal glands. From the perspective of embryogenesis, the medulla and sympathetic nerves are the same source, which is equivalent to a sympathetic ganglion, which is dominated by the previsceral ganglia fibers (sympathetic nerves), forming the sympathetic nerve-adrenal system.

Adrenal medullary glandular cells are large, polygonal, and arranged in clusters or irregular cords around the sinusoid (see Figure 13-10). The cells contained fine particles. After the treatment with chromium salt, some particles reacted with the chromium salt in brown. Cells containing such particles are called chromaffin cells. These particles may be the substance of the adrenomedullin

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1. Biological effects Adrenal medulla chromaffin cells secrete two hormones: adrenaline and norepinephrine, the ratio of which is about 4: 1, mainly adrenaline. They are all tyrosine-derived amines and have catechol groups in the molecule, so they are all catecholamines. Their biological effects are closely related to the sympathetic nervous system and have a wide range of functions. The famous scholar Cannon once proposed the emergency doctrine. he

Adrenal medulla

It is proposed that when the body encounters an emergency situation, such as fear, fright, anxiety, trauma or blood loss, the sympathetic nerve activity is strengthened, and the medullary hormone secretion increases sharply. The results are: increased heartbeat, increased cardiac output, increased blood pressure, and increased blood flow; visceral vasoconstriction, decreased blood flow to internal organs; muscle vasodilation, increased muscle blood flow, and more oxygen and nutrients to the muscle; Bronchodilation to reduce resistance to gas exchange and improve oxygen supply; breakdown of liver glycogen, elevated blood sugar, and increased supply of nutrients. The above-mentioned functional changes caused by the emergency response will help the body to fight against adverse conditions and escape from danger. The various stimuli that cause an emergency response are also stimuli that cause a stress response. In the above situation, the two response systems complement each other and both react, which completes the body's adaptive ability.

2. Myelin hormone secretion regulates excitability of precholinergic fibers in the visceral large ganglia, or acetylcholine can promote adrenal medullary synthesis and secrete adrenaline and norepinephrine. In the emergency response, norepinephrine in the blood mainly comes from the sympathetic nerve endings. Adrenaline and norepinephrine both have a negative feedback effect on the adrenal medulla. When they are synthesized in the cell to a certain amount, they can inhibit their synthesis. ACTH was found to promote adrenal medulla hormone synthesis directly, or indirectly through glucocorticoids.