NEUROANATOMY OF HEART IN HUMAN AND MAMMALIANS

Abstract

On reaching the heart, extrinsic cardiac nerves relay their signal to a network of autonomic ganglia situated throughout the epicardial surface. These ganglia interconnect and form a complex intrinsic ganglionated neural plexus responsible for integrating central and local inputs and relaying this signal to the cardiac conduction system, coronary vessels, heart valves and contractile muscle fibres. Within the human heart this intracardiac plexus could be defined in terms of seven subplexuses located and innervating discrete areas of the heart. Despite some noticeable адам мен interspecific differences in the overall neuronal number and ganglionic morphology, this type of structural organization is conserved throughout the mammalian heart. Intrinsic ganglionated plexus consists of neurons expressing various modulatory agents. It is widely accepted that most intracardiac neuronal somata are cholinergic, yet nearly half of them are biphenotypic for either tyrosine hydroxylase or neuronal nitric oxide synthase. Moreover exclusively tyrosine hydroxylase positive somata are found in some mammals and human hearts. Therefore in addition to relaying preganglionic vagal impulses, cardiac ganglia also integrate sensory and sympathetic inputs for rapid temporal reflexes and local regulation of heart rate on a beat-to-beat basis. The epicardium, in addition to numerous ganglia, is the main milieu for distribution of nerves towards the heart apex. The myocardium contains both scarce nerves located in the vicinity of blood vessels and a meshwork of fine nerve fibers. The endocardium contains a dense network of nerve fibers and nerve bundles with only a small part of them coalescing into nerves. The described structural organization of intracardiac nervous system provides an anatomical basis of the autonomic control of circulation.