Anaes · Applied cardiovascular & respiratory physiology

Autonomic nervous system

Also known as Sympathetic nervous system · Parasympathetic nervous system · Adrenergic receptors · Cholinergic receptors · Alpha beta receptors · Muscarinic nicotinic

The autonomic nervous system governs the involuntary organs and is the framework for almost every anaesthetic drug and reflex. The framework rests on five exam-critical ideas: the sympathetic outflow is thoracolumbar with short preganglionic and long postganglionic fibres and ganglia near the spine, while the parasympathetic outflow is craniosacral with long preganglionic and short postganglionic fibres and ganglia near or in the target organ; acetylcholine is the neurotransmitter at ALL autonomic ganglia and at the parasympathetic postganglionic synapse, while noradrenaline is the postganglionic sympathetic neurotransmitter (except the sweat glands, which are cholinergic); the adrenal medulla is a modified sympathetic ganglion that releases adrenaline into the blood; the adrenergic receptors (alpha-1 vasoconstrict, alpha-2 presynaptic-inhibit, beta-1 cardiac, beta-2 bronchodilator and vasodilator, beta-3 lipolysis and bladder) and the cholinergic receptors (nicotinic at ganglia and the neuromuscular junction, muscarinic at postganglionic parasympathetic targets) are G-protein-coupled with predictable second messengers and effects; and almost every anaesthetic intervention is an autonomic one — vasopressors, bronchodilators, anticholinergics, beta-blockers, neostigmine — and autonomic failure (diabetes, ageing) destabilises the perioperative patient. Built on the beta-2 adrenergic receptor cardiac study (Sanches 2026), the neurocardiac-autonomic TBI review (Gumbo 2026), the formoterol beta-2 study (Abourayya 2026), the sympathetic and parasympathetic ganglion-block study (Tyagi 2026), the geriatric anaesthesia study (Prado Fonseca 2026), the Ehlers-Danlos anaesthesia study (Unterman 2026), the adrenoceptor classification review (Hein 2006), the human muscarinic cardiovascular-control review (Palma 2024), and the muscarinic G-protein-class study (Mao 2023).