Chapt 13: Autonomic Nervous System (ANS) - Vocabulary Flashcards

Vocabulary flashcards covering key ANS terms, neurophysiology, pharmacology, and anesthesia implications from the lecture notes.

Autonomic Nervous System (ANS)

Branch of the peripheral nervous system that regulates involuntary visceral functions without conscious input; consists of the sympathetic and parasympathetic divisions.

Sympathetic Nervous System (SNS)

Division of the ANS that prepares the body for stress or emergencies; the ‘fight-or-flight’ system.

Parasympathetic Nervous System (PNS)

Division of the ANS that promotes rest and digestion; restores body after stress.

Somatic vs Autonomic distinction

Somatic uses a single motor neuron to skeletal muscle with acetylcholine; ANS uses two neurons (preganglionic and postganglionic) with a ganglion and uses acetylcholine and norepinephrine at the effector.

Preganglionic neuron

First neuron in the autonomic two-neuron chain; originates in the CNS and synapses in a ganglion.

Postganglionic neuron

Second neuron in the autonomic chain; innervates the effector organ; releases norepinephrine in the SNS and acetylcholine at many parasympathetic targets.

Ganglion

Synaptic relay point between the preganglionic and postganglionic neurons in the ANS.

Adrenal medulla

Modified sympathetic ganglion; preganglionic fibers synapse on chromaffin cells to release epinephrine and norepinephrine into circulation.

Chromaffin cells

Cells in the adrenal medulla that secrete epinephrine and norepinephrine.

Thoracolumbar division

SNS origin from thoracic (T1–T12) and upper lumbar (L1–L3) spinal cord.

Craniosacral division

PNS origin from cranial nerves III, VII, IX, X and sacral nerves; ‘craniosacral’ designation.

Vagus nerve

Major parasympathetic nerve supplying most thoracic and abdominal viscera; regulates heart rate, bronchomotor tone, GI secretions/motility.

Cholinergic receptors

Receptors activated by acetylcholine; include nicotinic and muscarinic types.

Nicotinic receptors

Cholinergic receptors found at all autonomic ganglia; always excitatory.

Muscarinic receptors

Cholinergic receptors on parasympathetic effector tissues; can be excitatory or inhibitory.

Adrenergic receptors

Receptors for norepinephrine/epinephrine; include alpha and beta subtypes.

Alpha1 receptor

Adrenergic receptor causing vasoconstriction and increased blood pressure.

Alpha2 receptor

Adrenergic receptor providing feedback inhibition of norepinephrine release.

Beta1 receptor

Adrenergic receptor increasing heart rate and contractility.

Beta2 receptor

Adrenergic receptor causing bronchodilation, vasodilation, and increased glucose availability.

Sympathetic effects on the heart

Increased heart rate and contractile force under sympathetic stimulation.

Sympathetic effects on vessels and liver

Vasoconstriction increasing BP; liver glucose release via glycogenolysis/gluconeogenesis.

Parasympathetic effects on the heart

Decreased heart rate and force of contraction.

Parasympathetic effects on GI tract and bladder

Increased GI motility and secretions; bladder contraction facilitating urination/defecation.

Neostigmine

Anticholinesterase that increases acetylcholine at all cholinergic synapses; enhances parasympathetic outflow; risks include bradycardia and bronchospasm.

Anticholinergic agents (e.g., atropine, glycopyrrolate)

Drugs that inhibit parasympathetic activity to block bradycardia/arrest and reduce secretions.

Regional anesthesia and the ANS

Spinal/epidural blocks can abolish sympathetic outflow below the level of anesthesia, risking bradycardia and severe hypotension; paravertebral blocks are segmental; celiac plexus blocks can selectively inhibit abdominal sympathetic input.

General anesthesia effects on the ANS

Many agents reduce sympathetic outflow causing hypotension; efficacy varies by agent (e.g., ketamine may raise sympathetic tone; etomidate preserves it).