The Autonomic Nervous System (Chapter 16)

Vocabulary flashcards covering key terms and concepts from the Autonomic Nervous System lecture notes.

Autonomic Nervous System (ANS)

Involuntary branch of the peripheral nervous system that coordinates visceral functions and glands; consists of sympathetic and parasympathetic divisions.

Sympathetic Division (Thoracolumbar)

Thoracic and upper lumbar (T1–L2) division of the ANS; ganglia near the spinal cord; prepares body for ‘fight or flight’.

Parasympathetic Division (Craniosacral)

Cranial and sacral (brainstem and S2–S4) division of the ANS; ganglia near or within target organs; promotes ‘rest and digest’.

Preganglionic Neuron

Neuron whose cell body is in the brain or spinal cord and synapses on a postganglionic neuron in an autonomic ganglion.

Postganglionic Neuron

Neuron that extends from an autonomic ganglion to the effector organ.

Autonomic Ganglia

Collections of neuron cell bodies outside the CNS; include sympathetic chain ganglia, collateral ganglia, and adrenal medullae.

Sympathetic Chain Ganglia (Paravertebral)

Paired ganglia along the sides of the vertebral column containing postganglionic neurons; connect to spinal nerves.

Collateral (Prevertebral) Ganglia

Unpaired ganglia anterior to the vertebral column; innervate abdominal and pelvic organs.

Adrenal Medullae

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

Autonomic Plexus

Networks where sympathetic postganglionic fibers and parasympathetic preganglionic fibers mingle to innervate visceral organs.

Enteric Division (Enteric Nervous System)

Extensive neural network in the GI tract walls; can function independently of the CNS; includes sensory neurons, interneurons, and motor neurons.

Cholinergic

Term for neurons or synapses that use acetylcholine (ACh) as the neurotransmitter.

Adrenergic

Term for neurons or synapses that use norepinephrine (NE) or epinephrine (E) as neurotransmitters.

Acetylcholine (ACh)

Primary neurotransmitter released by preganglionic neurons in both divisions; also released by parasympathetic postganglionic neurons at NMJs.

Norepinephrine (NE)

Main neurotransmitter released by most sympathetic postganglionic neurons; binds adrenergic receptors on target cells.

Epinephrine (E)

Hormone released by the adrenal medulla; acts as a circulating sympathetic neurotransmitter.

Nicotinic Receptors

Cholinergic receptors on autonomic ganglion neurons; activated by ACh; typically excitatory.

Muscarinic Receptors

Cholinergic receptors on effectors in the parasympathetic pathway; G-protein coupled; can be excitatory or inhibitory.

Alpha Receptors (α-adrenergic)

Adrenergic receptors with subtypes α1 and α2; NE/E binding modulates vascular and organ smooth muscle activity.

Alpha1 Receptors

Cause excitation in target cells (e.g., vasoconstriction, increased Ca2+).

Alpha2 Receptors

Often inhibitory; lowers cAMP and can inhibit neurotransmitter release at presynaptic sites.

Beta Receptors (β-adrenergic)

Adrenergic receptors with subtypes β1, β2, β3; modulate metabolism, heart rate, smooth muscle tone, and lipolysis.

Beta1 Receptors

Increase heart rate and metabolic activity in cardiac/skeletal tissues.

Beta2 Receptors

Cause smooth muscle relaxation (e.g., bronchodilation, vasodilation).

Beta3 Receptors

Stimulate lipolysis in adipose tissue.

Nitroxidergic (NO) Synapses

Synapses that use nitric oxide as a neurotransmitter; promote vasodilation and increased blood flow.

Vagus Nerve (X)

Cranial nerve that provides major parasympathetic outflow; carries about 75% of parasympathetic activity.

Parasympathetic Tone

Baseline parasympathetic activity; generally dominates at rest, influencing heart rate, digestion, and glandular activity.

Long Visceral Reflex

Visceral reflex arc that involves CNS processing and interneurons to coordinate activity of an entire organ.

Short Visceral Reflex

Visceral reflex that bypasses the CNS, using peripheral ganglia to produce localized responses in organs (often via the Enteric Division).

Visceral Reflex Arc

Reflex pathway for autonomic control: receptor, sensory neuron, CNS processing center, two visceral motor neurons, and an effector.

Enteric Nervous System Details

Contains visceral sensory neurons, interneurons, and visceral motor neurons; capable of autonomous GI regulation but influenced by CNS.

Cardiac Plexus

Autonomic plexus around the heart integrating sympathetic and parasympathetic input.

Pulmonary Plexus

Autonomic plexus around the lungs supplying respiratory tissues.

Esophageal Plexus

Autonomic network around the esophagus to coordinate esophageal function.

Celiac (Solar) Plexus

Autonomic plexus around the celiac trunk supplying upper abdominal organs (stomach, liver, spleen, pancreas).

Superior Mesenteric Plexus

Autonomic plexus around the superior mesenteric artery; innervates the small intestine and parts of the large intestine.

Inferior Mesenteric Plexus

Autonomic plexus around the inferior mesenteric artery; innervates the large intestine and rectum.

Hypogastric Plexus

Autonomic plexus supplying pelvic organs (urinary, digestive, reproductive).

Intramural Ganglia

Parasympathetic ganglia embedded within the wall of target organs.

Terminal (Near-Target) Ganglia

Parasympathetic ganglia located near or in the wall of target organs.

Craniosacral (Parasympathetic)

Another term for the parasympathetic division based on its cranial and sacral origins.

Preganglionic Fiber Lengths (Sympathetic)

Short preganglionic fibers; long postganglionic fibers because ganglia lie near the CNS.

Postganglionic Fiber Lengths (Sympathetic)

Long postganglionic fibers that extend to target organs.

Preganglionic Fiber Lengths (Parasympathetic)

Long preganglionic fibers; short postganglionic fibers because ganglia are near target organs.

Postganglionic Fiber Lengths (Parasympathetic)

Short postganglionic fibers that reach the target organ.