Somatic vs. Autonomic Nervous Systems – Key Vocabulary

A set of 38 vocabulary flashcards summarizing essential terms and concepts from the lecture on somatic and autonomic nervous systems.

Somatic Nervous System

Division of the peripheral nervous system that controls skeletal muscles through voluntary, single-neuron, always-excitatory pathways using acetylcholine.

Autonomic Nervous System

Involuntary motor system regulating smooth muscle, cardiac muscle, and glands through two-neuron chains that release acetylcholine or norepinephrine and can excite or inhibit.

Voluntary Control

Conscious regulation of skeletal muscle activity characteristic of the somatic nervous system.

Involuntary Control

Automatic regulation of visceral functions performed by the autonomic nervous system.

Skeletal Muscles

Effector organs innervated exclusively by somatic motor neurons.

Smooth Muscle

Non-striated muscle in organs and vessels that is regulated by the autonomic nervous system.

Acetylcholine (ACh)

Neurotransmitter released by all somatic motor neurons and many autonomic neurons, especially parasympathetic.

Norepinephrine (NE)

Catecholamine secreted by most sympathetic postganglionic neurons and the adrenal medulla.

Excitatory Signal (Somatic)

Property that somatic motor neurons always stimulate, never inhibit, their target muscles.

Single-Neuron Pathway

Arrangement in the somatic system where one neuron extends from the CNS directly to the effector with no ganglion.

Two-Neuron Pathway

Typical autonomic arrangement consisting of a preganglionic neuron, a ganglion, and a postganglionic neuron.

Sympathetic Division

Thoracolumbar branch of the ANS that produces fight-or-flight responses and primarily uses norepinephrine/epinephrine.

Parasympathetic Division

Craniosacral branch of the ANS that promotes rest-and-digest activities and uses acetylcholine.

Thoracolumbar Outflow

Location of sympathetic preganglionic neuron cell bodies in the thoracic and lumbar spinal cord.

Craniosacral Outflow

Origin of parasympathetic preganglionic neurons in brain-stem cranial nerves and sacral spinal cord.

Sympathetic Ganglia

Clusters of neuron cell bodies located near the spinal cord where sympathetic synapses occur.

Parasympathetic Ganglia

Ganglia situated in or near the target organ where parasympathetic synapses occur.

Short Preganglionic Fiber (Sympathetic)

Characteristic length of sympathetic preganglionic axons, facilitating rapid, widespread effects.

Long Preganglionic Fiber (Parasympathetic)

Characteristic length of parasympathetic preganglionic axons, allowing localized control.

Fight-or-Flight Response

Body-wide sympathetic activation preparing for emergency action—elevated heart rate, blood pressure, etc.

Rest-and-Digest Response

Parasympathetic activity that conserves energy and enhances maintenance functions like digestion.

Cholinergic Fiber

Autonomic neuron that releases acetylcholine at its terminals.

Adrenergic Fiber

Autonomic neuron that releases norepinephrine (or epinephrine) at its terminals.

Muscarinic Receptor

G-protein-coupled cholinergic receptor on effector cells that can be excitatory or inhibitory.

Nicotinic Receptor

Ionotropic cholinergic receptor on all postganglionic neurons and skeletal muscle; always excitatory.

Alpha Adrenergic Receptor

Sympathetic receptor subtype responsive to NE/Epi, generally producing excitatory effects on target tissues.

Beta Adrenergic Receptor

Sympathetic receptor subtype responsive to NE/Epi, producing variable effects—excitatory in heart, inhibitory in some smooth muscle.

Heart Rate – Sympathetic Effect

Sympathetic stimulation increases heart rate and arterial blood pressure.

Heart Rate – Parasympathetic Effect

Parasympathetic stimulation decreases heart rate and arterial blood pressure.

Digestion – Sympathetic Effect

Sympathetic activity inhibits gastrointestinal motility and secretion.

Digestion – Parasympathetic Effect

Parasympathetic activity stimulates gastrointestinal motility and secretion.

Bronchiole Dilation

Widening of airway passages produced by sympathetic stimulation of lung smooth muscle.

Bronchiole Constriction

Narrowing of airway passages caused by parasympathetic stimulation of lung smooth muscle.

Vasodilation to Muscles & Brain

Sympathetic-induced widening of blood vessels supplying skeletal muscles and the brain.

Vasoconstriction to Digestive System & Skin

Sympathetic-induced narrowing of vessels supplying the gut and skin, diverting blood to critical areas.

Adrenal Medulla

Inner region of the adrenal gland that releases epinephrine and norepinephrine when stimulated by sympathetic preganglionic fibers.

Epinephrine

Hormone and neurotransmitter secreted by the adrenal medulla that reinforces sympathetic responses throughout the body.

Hypothalamus (ANS Control)

Brain region that integrates visceral sensory information and orchestrates overall autonomic nervous system output.