![]() One can imagine, that given the anatomical differences between the 2 divisions, anaesthetic interventions may have a greater or lesser effect on the sympathetic or parasympathetic nerves. The basic structure of the ANS is illustrated in the diagram below. Sacral preganglionic fibres emerge from the CNS via the ventral rami of nerves S2-S4 and form the pelvic splanchnic nerves, which pass to ganglia close to the effector organs. Consequently, in contrast to the sympathetic nervous system, preganglionic fibres tend to be long, whereas postganglionic fibres will be shorter. The fibres travel with the main body of the cranial nerves to ganglia that tend to be more distant from the CNS and close to the target organ. Cranial fibres arise from specific parasympathetic brainstem nuclei of cranial nerves III, VII, IX, and X. Parasympathetic preganglionic fibres leave the CNS in both cranial and sacral nerves the so-called “cranio-sacral outflow”. In general therefore, sympathetic preganglionic fibres are short, and postganglionic fibres tend to be longer. Some preganglionic fibres however ascend or descend to other levels of the sympathetic chain prior to synapsing. In the sympathetic chain the fibres will synapse, giving rise to unmyelinated post-ganglionic fibres that rejoin the spinal nerves via the grey rami communicantes. These fibres emerge from the spinal cord in the primary ventral rami of the spinal nerves and pass to the sympathetic chain via the white rami communicantes. Preganglionic sympathetic fibres have cell bodies in the intermedio- lateral horn of grey matter in the spinal cord between T1 & L2. ![]() In the sympathetic nervous system, the ganglia are fused to form the sympathetic chain, which lies adjacent to the spinal column throughout most of its length. In addition to its close functional relationship to the central nervous system, the ANS shares a close anatomical proximity. Structure of the Autonomic Nervous System The respiratory system and CNS are also depressed. The cardiovascular system is depressed – reducing heart rate and cardiac output, and routing blood flow toward visceral beds. The parasympathetic nervous system in contrast, increases the activity of the abdominal viscera. ![]() There is an overall increase in CNS stimulation, and respiratory drive is increased. In the cardiovascular system, increased inotropic and chronotropic drive lead to increased cardiac output and blood flow is routed toward vital organs and skeletal muscle. In general the sympathetic nervous system can be thought of as preparing the body for “fight or flight”. These two divisions differ in both structure and function as will be seen later. The “effector limb” of the ANS is subdivided in to 2 separate divisions – the sympathetic, and parasympathetic nervous systems. These postganglionic fibres mediate the desired response at the effector organ. The efferent limb of neuronal autonomic reflexes consists of specific primary autonomic nerves that synapse in autonomic ganglia, with secondary or “postganglionic” fibres. ii) The Central Nervous System – for example the “vaso-vagal response” to impending cannulation in a needle-phobic patient.i) The Autonomic Nervous System – for example the tachycardia in response to hypotension, mediated by baroreceptors, or –.The afferent input to the reflex arc varies and can be from: In general, ANS effects are involuntary, relatively rapid, neuronal reflexes. The ANS can thus be thought of as the regulatory system, that partly or wholly controls most of the body’s organ systems and homeostatic mechanisms. These functions are controlled subconsciously, with a degree of automaticity, by a branch of the nervous system – The Autonomic Nervous system (ANS). For example, we don’t have to remember to digest our food after a meal, or sweat when too warm. Many bodily functions proceed without any conscious supervision from our central nervous system (CNS). What types of receptors are there in the autonomic nervous system?.What are the transmitter substances in the autonomic nervous system?.How do parasympathetic nerves get from the CNS to end organs?.How do sympathetic nerves get from the CNS to the end organs?. ![]() What is the autonomic nervous system and what are its functions?.It is therefore essential that the anaesthetist should have a basic understanding of its structure and function.īefore reading the tutorial, see what you already know about this subject by answering the following questions: If they are in the Post.Many anaesthetic procedures and drugs used in anaesthetic practice have a direct influence on the autonomic nervous system. Collective links are provided in 2 or 3 Different Clouds at the end of Each Post.Ģ–> Click On The Images To Enlarge Them. Individual files links are of Google Drive. 1–> All the Links to the Files are Linked to Cloud Server e.g, Google Drive, Mega, Dropbox Or Media fire. ![]()
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