Organization of the Somatic and Autonomic Motor Divisions

Practice vocabulary flashcards covering the somatic motor division, autonomic nervous system, gut tube embryonic subdivisions, and splanchnic pathways from Lecture 20.

Somatic Motor Division

The voluntary motor division of the peripheral nervous system where a single somatic motor neuron extends directly from the central nervous system to innervate skeletal muscle.

Visceral Motor Division

The autonomic nervous system (ANS) that directs involuntary control of smooth muscle, cardiac muscle, and glands using a two-neuron chain from the central nervous system to effector organs.

Dual Innervation

The autonomic arrangement where visceral organs are served by both sympathetic and parasympathetic divisions, producing opposite physiological effects.

Preganglionic Neuron

An autonomic motor neuron whose cell body is located within the central nervous system (brainstem or spinal cord) and whose axon travels to synapse in an autonomic ganglion.

Postganglionic Neuron

An autonomic motor neuron whose cell body resides in an autonomic ganglion outside the central nervous system and whose axon projects directly to target effector cells.

Parasympathetic Division

The branch of the ANS responsible for conserving body energy during maintenance activities ('rest and digest') that originates from craniosacral outflow, featuring long preganglionic neurons and short postganglionic neurons.

Sympathetic Division

The branch of the ANS that mobilizes the body during exercise, emergency, excitement, fear, and stress ('fight or flight') through thoracolumbar outflow, featuring short preganglionic neurons and long postganglionic neurons.

Craniosacral Outflow

The anatomical distribution of the parasympathetic division consisting of cranial nerves III, VII, IX, and X, together with sacral spinal cord segments S2–S4.

Thoracolumbar Outflow

The anatomical distribution of the sympathetic division emerging from spinal nerve segments T1–T12 and L1–L5.

Sympathetic Trunk

A paired chain of sympathetic ganglia located along the right and left sides of the vertebral column.

Splanchnic Nerves

Preganglionic sympathetic axons that pass through the sympathetic trunk without synapsing to innervate abdominal and pelvic viscera at preaortic ganglia.

Greater Splanchnic Nerve

A splanchnic nerve arising from spinal levels T5–T9 that provides preganglionic sympathetic innervation to foregut organs.

Lesser Splanchnic Nerve

A splanchnic nerve arising from spinal levels T10–T11 that provides preganglionic sympathetic innervation to midgut and hindgut organs.

Least Splanchnic Nerve

A splanchnic nerve arising from spinal level T12 that provides sympathetic innervation to hindgut organs.

Lumbar Splanchnic Nerves

Splanchnic nerves emerging from spinal levels L1–L2 that innervate hindgut and urogenital organs.

Preaortic Ganglia

Prevertebral sympathetic ganglia situated anterior to the abdominal aorta where splanchnic nerves terminate and synapse with postganglionic neurons.

Celiac Ganglia

Preaortic ganglia positioned adjacent to the celiac trunk artery that supply sympathetic fibers to foregut organs.

Superior Mesenteric Ganglia

Preaortic ganglia positioned adjacent to the superior mesenteric artery that supply sympathetic fibers to midgut organs.

Inferior Mesenteric Ganglia

Preaortic ganglia positioned adjacent to the inferior mesenteric artery that supply sympathetic fibers to hindgut organs.

Foregut

The embryonic gut division extending from the mouth to the duodenum, partitioned by rapid head bending toward the ventral surface.

Midgut

The embryonic gut division extending from the jejunum to the left colic flexure of the transverse colon.

Hindgut

The embryonic gut division extending from the descending colon to the anus, partitioned by tail bending toward the ventral surface.

Coelom

The embryonic cavity that splits lateral plate mesoderm, surrounds the gut tube, and develops into the ventral body cavity.

Somatopleure

The embryonic layer that lifts away from the yolk sac as its lateral edges fold ventrally, fusing to enclose the embryo into a tube.

Neuromuscular Junction (NMJ)

The anatomical site of communication between a somatic motor neuron's synaptic end bulb and the motor end plate of a skeletal muscle fiber.