Autonomic Nervous System

Somatic nervous system

The part of the nervous system that causes voluntary contraction of skeletal muscles

Autonomic nervous system

The part of the nervous system that controls involuntary contraction of cardiac muscle, smooth muscle, and glandular tissue

Preganglionic neuron

The first neuron in the pathway, running from the spinal cord to the ganglion

Preganglionic axon

Axon associated with the first neuron in the pathway, short for sympathetic and long for parasympathetic

Ganglion

Collection of cell bodies where synapses occur

Postganglionic neuron

The second neuron in the pathway, runs from ganglion to the effector

Postganglionic axon

Axon associated with the second neuron in the pathway, long for sympathetic and short for parasympathetic

Acetylcholine

Neurotransmitter used for synapses: between pre- and post- ganglionic neurons in both the parasympathetic and sympathetic divisions, and between the postganglionic neuron and the effector for only the parasympathetic division

Dual innervation

Receiving innervation from both the parasympathetic and sympathetic divisions, activity of the effector is determined by which division is more active at that time

Referred pain

Irregular pattern of projection of conscious perception of visceral sensations, pain in the organs perceived to be in the skin

Plexus

A web of intertwining axons and nerves traveling to their destination, all contain axons from both divisions

Cardiac plexus

Most superior plexus, fibers travel to the heart

Esophageal plexus

Plexus just superior to the diaphragm, fibers travel to the thoracic esophagus

Pulmonary plexus

Second-most superior plexus, fibers travel to the lungs and bronchi

Abdominal aortic plexuses

Group of plexuses that include the celiac, superior mesenteric, and inferior mesenteric plexuses

Celiac plexus

Most superior plexus below the diaphragm, fibers travel to the foregut organs

Superior mesenteric plexus

Second-most superior plexus below the diaphragm, fibers travel to the midgut organs

Inferior mesenteric plexus

Most inferior plexus that leads to the abdomen, fibers travel to the hindgut organs

Hypogastric plexus

Most inferior plexus, fibers travel to the pelvic organs

Parasympathetic Division

Division associated with rest and digest, conserving energy, and conducting routine maintenance, postganglionic neurons are in or next to the target organs

Craniosacral

Another name for the parasympathetic division

Vagus nerve

Cranial nerve X, provides parasympathetic innervation to the thoracic organs and most abdominal organs, fibers travel through all plexuses above diaphragm and also the C and SM plexuses

Pelvic splanchnic nerves

Provides parasympathetic innervation to the distal aspect of the digestive tract and pelvic organs, fibers travel through the two most inferior plexuses

Sympathetic Division

Division associated with fight and flight, active during stress and also exercise

Thoracolumbar

Another name for the sympathetic division

Sympathetic chain (trunk)

Structure of sympathetic nervous tissue that runs alongside the vertebral column, extends above and below the origins in the cervical and thoracic regions

Sympathetic chain ganglia

Swellings along the sympathetic chain composed of neuronal bodies

Norepinephrine/Epinephrine

Neurotransmitter used for synapses between postganglionic neurons and the effector in the sympathetic division only

Superior, middle, inferior cervical ganglion

Three sympathetic ganglia that extend superiorly past the T1 level

White rami communicantes

Part of the sympathetic chain composed of preganglionic sympathetic axons of the T1-L2 spinal nerves, myelinated

Gray rami communicantes

Part of the sympathetic chain composed of postganglionic sympathetic axons from the sympathetic trunk to the spinal nerve, unmyelinated

Splanchnic nerves

Fibers in these nerves originate from the T5-L2 levels and travel to prevertebral ganglia

Greater thoracic splanchnic nerve

Fibers in this nerve originate from T5-T9 and travel to the celiac ganglion, synapse there, and travel to the celiac plexus

Lesser thoracic splanchnic nerve

Fibers in this nerve originate from T10-T11 and travel to the superior mesenteric ganglion, synapse there, and travel to the superior mesenteric plexus

Least thoracic splanchnic nerve

Fibers in this nerve originate from T12 and travel to the superior or inferior mesenteric ganglion and synapse there

Lumbar splanchnic nerves

Fibers in this nerve originate from L1-L2 and travel to the inferior mesenteric ganglion, synapse there, and travel to the inferior mesenteric plexus

Sacral splanchnic nerves

Fibers in these nerves originate from the sacral extension of the sympathetic chain, synapse in the chain ganglia, and travel to the hypogastric plexus

Prevertebral ganglia

Ganglia situated anterior to the vertebral column, receive inputs from splanchnic nerves, control organs in the abdominal cavity

Celiac ganglia

Prevertebral ganglia, fibers travel to the foregut after synapsing

Superior mesenteric ganglia

Prevertebral ganglia, fibers travel to the midgut after synapsing

Inferior mesenteric ganglia

Prevertebral ganglia, fibers travel to the hindgut after synapsing

Spinal nerve pathway

Sympathetic pathway that synapses in the chain ganglia, then use the grey rami communicantes to go back to the spinal nerve and innervate the skin, originates from T1-L2

Postganglionic sympathetic pathway

Sympathetic pathway that originates from T1-T5, fibers ascend to middle and inferior cervical ganglia, synapse there, and travel to the esophageal, cardiac, and pulmonary plexuses

Splanchnic nerve pathway

Fibers in this pathway originate from the sacral extension of the sympathetic chain, synapse in the chain ganglia, and travel to the hypogastric plexus

Adrenal medulla pathway

Only sympathetic pathway without a ganglion, axons travel to the adrenal medulla and cause it to release norepinephrine into the bloodstream to communicate with target structures

Adrenal gland

Pyramid-shaped gland on the superior border of the kidneys

Adrenal medulla

Portion of the adrenal gland that releases norepinephrine and epinephrine