Autonomic and Somatic Nervous Systems Vocabulary

A comprehensive vocabulary review of the somatic and autonomic nervous systems, including anatomical structures, divisions, autonomic pathways, plexuses, and visceral reflexes from the lecture notes.

Somatic nervous system (SNS)

The system that consciously senses and controls processes, involving a somatic sensory portion that detects signals from special senses, skin, and proprioceptors, and a somatic motor portion that sends signals from the CNS to skeletal muscles.

Autonomic nervous system (ANS)

Also called the autonomic motor or visceral motor system; processes regulated below the conscious level that transmit signals from the CNS to heart, smooth muscle, and glands to maintain homeostasis.

Preganglionic neuron

The first motor neuron in the ANS chain, with its cell body in the brainstem or spinal cord and a thin, myelinated axon that releases ACh from its synaptic knob to excite the second motor neuron.

Ganglionic neuron

The second motor neuron in the ANS chain (also called postganglionic neuron), with its cell body in an autonomic ganglion and a very thin, unmyelinated axon that releases ACh or norepinephrine (NE) to excite or inhibit an effector.

Neuronal convergence

An ANS structural feature where multiple preganglionic neurons synapse on a single ganglionic neuron.

Neuronal divergence

An ANS structural feature where axon branches from one preganglionic neuron synapse with numerous ganglionic neurons.

Parasympathetic division

The craniosacral division of the ANS responsible for 'rest-and-digest' functions, which conserves energy and replenishes nutrient stores.

Sympathetic division

The thoracolumbar division of the ANS responsible for 'fight-or-flight' responses during exercise, excitement, or emergency.

Terminal ganglia

Parasympathetic autonomic ganglia located close to the effector organ.

Intramural ganglia

Parasympathetic autonomic ganglia located within the wall of the target organ.

Oculomotor Nerve (CN III)

Cranial nerve conveying parasympathetic preganglionic axons from midbrain nuclei to the ciliary ganglion to control the ciliary muscle and pupil constriction.

Facial Nerve (CN VII)

Cranial nerve conveying parasympathetic preganglionic axons from the pons to pterygopalatine and submandibular ganglia, controlling lacrimal glands, nasal/oral glands, and submandibular/sublingual salivary glands.

Glossopharyngeal Nerve (CN IX)

Cranial nerve conveying parasympathetic preganglionic axons from the medulla to the otic ganglion to control the parotid salivary gland.

Vagus Nerve (CN X)

Cranial nerve conveying parasympathetic preganglionic axons from the medulla to ganglia in the thorax and abdomen, slowing heart rate, constricting lung bronchioles, and increasing digestive secretions.

Pelvic splanchnic nerves

Nerves composed of preganglionic parasympathetic axons from S2-S4 that project to terminal or intramural ganglia, influencing smooth muscle contraction and secretions in digestive, urinary, and reproductive effectors.

Superior cervical ganglion

A cervical sympathetic trunk ganglion housing cell bodies whose postganglionic axons project to head, neck, and thoracic targets, such as sweat glands, blood vessels, dilator pupillae muscle, and superior tarsal muscle.

Autonomic tone

The continuous background release of neurotransmitters by both ANS divisions to maintain ongoing control over effector status.

Dual innervation

The state of an organ receiving motor input from both the sympathetic and parasympathetic divisions, producing either antagonistic or cooperative effects.

Cardiac plexus

An autonomic network containing sympathetic axons from the cervical and thoracic trunk (to quicken heart rate) and parasympathetic axons from the vagus nerve (to slow heart rate).

Pulmonary plexus

An autonomic network containing sympathetic axons that cause bronchodilation and parasympathetic axons from the vagus nerve that cause bronchoconstriction.

Esophageal plexus

An autonomic network containing sympathetic axons that decrease motility and parasympathetic axons from the vagus nerve that coordinate opening of the cardiac sphincter during swallowing.

Abdominal aortic plexus

An autonomic network consisting of the celiac, superior mesenteric, and inferior mesenteric plexuses that innervates all abdominal and some pelvic organs.

Hypogastric plexus

An autonomic network consisting of sympathetic axons from the aortic plexus and sympathetic trunk, as well as parasympathetic axons from pelvic splanchnic nerves, innervating pelvic viscera.

Autonomic reflexes

Pre-programmed responses to stimuli generated by a visceral reflex arc involving receptors, sensory relays, integration centers, motor neurons, and cardiac, smooth muscle, or gland effectors.

Cardiovascular reflex

An autonomic reflex where stretch receptors respond to elevated blood pressure by signaling the cardiac center in the medulla oblongata to inhibit sympathetic and activate parasympathetic output, slowing heart rate and reducing blood pressure.

Micturition reflex

An autonomic reflex where stretch receptors signal bladder filling to the sacral spinal cord, triggering reflexive contraction of bladder smooth muscle and relaxation of urinary sphincters.