Autonomic regulation of medullary neurons following cardiorespiratory, glucoprivic and hypoglycaemic insults

Abstract

The autonomic nervous system (ANS) consists of two divisions: the sympathetic (SNS) and the parasympathetic (PNS) nervous systems. Signal transduction in the ANS requires integration of sensory afferent information from the periphery, central nervous system and spinal cord. Efferent fibres of presynaptic parasympathetic neurons arise from the brainstem and sacral (‘craniosacral’) levels of the spinal cord. There are 5 cranial nerves (CN) that arise from cell bodies located in the Edinger-Westphal nuclei (CN III), superior salivatory nuclei (CN VII), inferior salivatory nuclei (CN IX) and the dorsal motor nuclei of the vagus (CN X), and the nuclei ambiguus of the ventrolateral medulla oblongata (CN X). Sympathetic nerve fibres originate from the remaining thoracolumbar regions in the spinal cord (T1-L3). The sympathetic preganglionic neurons (SPN) residing in the intermediolateral thoracic spinal cord (T5-T12) are relayed via the greater (T5-T9), lesser (T10-T11) and least (T12) splanchnic nerves. The greater splanchnic nerve contains preganglionic fibres that synapse onto the celiac and superior mesenteric ganglion, with the exception of a unique set of long preganglionic sympathetic fibres (forming the adrenal nerve) that synapse onto chromaffin cell bodies in the adrenal medulla. This thesis will focus on diseases and conditions arising from two systems governed by the ANS; namely the cardiorespiratory and endocrine systems. The aim of the introduction is to introduce the essential features (functional anatomy and physiology) of the ANS in terms of the cardiorespiratory and neuroendocrine systems. Secondly, a pathological condition with unknown mechanisms associated with dysfunction of the ANS in each of the cardiorespiratory and neuroendocrine systems will be introduced as separate sub-chapters. Finally, the specific aims and results of the relevant studies will be provided, with emphasis placed on SNS and neuropeptidergic control in each condition.