Introduction to the Autonomic Nervous System – Key Vocabulary

Forty vocabulary flashcards covering anatomical, physiological, and functional terms introduced in the lecture on the autonomic nervous system.

Autonomic Nervous System (ANS)

Involuntary motor system that regulates visceral functions via sympathetic, parasympathetic, and enteric divisions.

Somatic Nervous System (SNS)

Voluntary motor and conscious sensory system that innervates skin, joints, and skeletal muscle.

General Visceral Efferent (GVE)

Autonomic motor fibers that carry signals from the CNS to smooth muscle, cardiac muscle, or glands.

General Visceral Afferent (GVA)

Sensory fibers that return information from visceral organs to the CNS, often unconscious or dull pain.

General Somatic Efferent (GSE)

Motor fibers that drive contraction of skeletal (striated) muscle.

General Somatic Afferent (GSA)

Sensory fibers that convey touch, pain, temperature, and proprioception from body wall and limbs.

Preganglionic neuron

First neuron in an autonomic pathway; cell body in CNS, axon projects to an autonomic ganglion.

Postganglionic neuron

Second neuron in an autonomic pathway; cell body in PNS ganglion, axon projects to target organ.

Sympathetic Division

Thoracolumbar branch of ANS that mediates "fight or flight" responses; generally increases heart rate and respiration, decreases digestion.

Parasympathetic Division

Craniosacral branch of ANS that mediates "rest and digest" responses; generally decreases heart rate and increases GI activity.

Enteric Nervous System

Network of neurons within the GI tract that can function independently of the CNS to regulate digestion.

Thoracolumbar Outflow

Sympathetic pre-ganglionic cell bodies located in spinal cord levels T1–L2/3.

Craniosacral Outflow

Parasympathetic pre-ganglionic cell bodies located in brainstem (CN III, VII, IX, X) and sacral spinal cord (S2–S4).

Intermediolateral Cell Column (Lateral Horn)

Spinal cord gray matter region containing sympathetic pre-ganglionic neurons from T1 to L2.

Sympathetic Chain (Sympathetic Trunk)

Bilateral vertical series of paravertebral ganglia extending from cervical to sacral regions.

White Ramus Communicans

Myelinated pathway through which sympathetic pre-ganglionic axons leave spinal nerves to enter the sympathetic chain (present only T1–L2).

Gray Ramus Communicans

Unmyelinated pathway through which sympathetic post-ganglionic axons rejoin spinal nerves for distribution to body wall (present at every spinal level).

Paravertebral Ganglia

Autonomic ganglia located in the sympathetic chain alongside the vertebral column.

Prevertebral (Collateral) Ganglia

Autonomic ganglia located anterior to the aorta (e.g., celiac, superior mesenteric) that receive splanchnic nerves.

Splanchnic Nerve

Bundle of autonomic fibers (sympathetic or parasympathetic) that passes from the sympathetic chain or sacral spinal cord to a visceral plexus or ganglion.

Cardiopulmonary Splanchnic Nerves

T1–T5 sympathetic post-ganglionic fibers that innervate heart, lungs, and esophagus.

Greater Thoracic Splanchnic Nerve

T5–T9 sympathetic pre-ganglionic fibers projecting to celiac ganglion and adrenal medulla.

Lesser Thoracic Splanchnic Nerve

T10–T11 sympathetic pre-ganglionic fibers projecting mainly to aorticorenal and superior mesenteric ganglia.

Least Thoracic Splanchnic Nerve

T12 sympathetic pre-ganglionic fibers projecting to renal plexus.

Lumbar Splanchnic Nerves

L1–L3 sympathetic pre- or post-ganglionic fibers that supply pelvic and lower abdominal viscera.

Sacral Splanchnic Nerves

Sympathetic fibers descending to sacral chain ganglia that innervate pelvic organs.

Pelvic Splanchnic Nerves

S2–S4 parasympathetic pre-ganglionic fibers that supply distal colon, bladder, and reproductive organs.

Superior Cervical Ganglion

Most superior sympathetic chain ganglion; source of post-ganglionic fibers to head via internal carotid plexus.

Stellate (Cervicothoracic) Ganglion

Fusion of inferior cervical and first thoracic sympathetic ganglia; supplies upper limbs and heart.

Celiac Ganglion

Large prevertebral ganglion around celiac trunk; distributes sympathetic fibers to foregut organs and adrenal medulla.

Superior Mesenteric Ganglion

Prevertebral ganglion supplying sympathetic fibers to midgut organs.

Inferior Mesenteric Ganglion

Prevertebral ganglion supplying sympathetic fibers to hindgut organs.

Referred Pain

Visceral pain perceived at a somatic location due to convergence of visceral and somatic afferents on the same spinal segment.

Dermatome

Skin area supplied by sensory fibers of a single spinal nerve; used to map referred pain patterns.

Visceral Afferent Pain Pathway

GVA fibers that travel with sympathetic nerves to convey nociceptive signals to dorsal root ganglia.

Physiologic Visceral Afferents

GVA fibers that carry innocuous information (e.g., pressure, chemical changes) and often travel with parasympathetic nerves.

Cholinergic Neuron

Neuron that releases acetylcholine; describes all pre-ganglionic ANS neurons and parasympathetic post-ganglionic neurons.

Adrenergic Neuron

Neuron that releases norepinephrine; describes most sympathetic post-ganglionic neurons.

"Rest and Digest" Response

Physiological state promoted by parasympathetic activity: decreased heart rate, increased GI motility, pupil constriction.

"Fight or Flight" Response

Physiological state promoted by sympathetic activity: increased heart rate, dilated pupils, bronchodilation, decreased digestion.

Sympathic Chain of Ganglion

A series of connected ganglia located alongside the vertebral column that are involved in the sympathetic nervous system, facilitating quick neuronal communication. Axon enters ganglia from spinal cord via white ramus and synapses with postganglionic neurons.

What are the 3 sympathetic innervation routes

Pathways through which sympathetic fibers extend from the spinal cord to various target organs, primarily involving preganglionic and postganglionic neurons.

Referred Pain

Pain perceived at a location different from the source. It often occurs because multiple sensory nerves converge at the spinal cord.