The parenchyma of the adrenal medulla is composed of chromaffin cells, which are modified postganglionic sympathetic neurons. The adrenal medulla is the central portion of the adrenal gland. Carmichael, in Principles of Medical Biology, 1997 Summary In these ways the adrenal medulla and its hormones really do lie at the interface between hormonal and neural communication. However, the actions of the medullary hormones are far more rapid and short-lived than those of most hormones. So the adrenal medulla also functions like a conventional endocrine gland. However, the catecholamines of the adrenal medulla are released into blood, rather than a synaptic cleft, and act at sites distant from the site of secretion, by activating specific receptors. So the medulla functions like a modified sympathetic ganglion. The adrenal medulla itself is modified neural tissue and its activity is regulated by a direct neural input. The hormones of the adrenal medulla are the catecholamines, which also function as classical neurotransmitters in the autonomic nervous system. The adrenal medulla is at the interface between the neural and endocrine systems and has features of both. Shern Chew BSc MD FRCP, in The Endocrine System (Second Edition), 2010 Introduction
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