Autonomic & Somatic Nervous System Vocabulary

A set of vocabulary flashcards covering the key terms and definitions from the lecture on the autonomic and somatic nervous systems, including their divisions, neurotransmitters, receptors, and associated physiological responses.

Sympathetic Nervous System

Division of the autonomic nervous system that prepares the body for stress; produces the fight-or-flight response.

Parasympathetic Nervous System

Division of the autonomic nervous system that conserves energy and promotes routine maintenance; produces the rest-and-digest response.

Fight-or-Flight Response

Physiological changes (e.g., ↑ heart rate, bronchodilation, pupil dilation) triggered by sympathetic stimulation during stress or danger.

Rest-and-Digest Response

State promoted by parasympathetic activity in which heart rate slows, GI activity rises, and the body focuses on maintenance functions.

Dual Innervation

Condition in which an organ receives nerve fibers from both the sympathetic and parasympathetic divisions, often producing opposing effects.

Somatic Nervous System

Motor system that provides voluntary control of skeletal muscles via a single, myelinated lower motor neuron releasing acetylcholine.

Autonomic Nervous System (ANS)

Involuntary motor system regulating cardiac muscle, smooth muscle, and glands through two-neuron chains.

Preganglionic Neuron

First motor neuron of an autonomic pathway; cell body in CNS, axon exits via cranial or spinal nerve to an autonomic ganglion.

Postganglionic Neuron

Second motor neuron of an autonomic pathway; unmyelinated axon extends from ganglion to the effector organ.

Autonomic Ganglion

Peripheral collection of neuronal cell bodies where pre- and postganglionic neurons synapse.

Sympathetic Trunk (Chain)

Longitudinal bundle of sympathetic ganglia and fibers running alongside the vertebral column, linking spinal nerves to organs.

Prevertebral Ganglia

Sympathetic ganglia located anterior to the vertebral column on the abdominal aorta (e.g., celiac ganglion).

Hypothalamus

Brain region that serves as the primary control center of the autonomic nervous system.

Catecholamines

Biogenic amines—norepinephrine, epinephrine, and dopamine—acting as hormones or neurotransmitters.

Norepinephrine (Noradrenaline)

Primary neurotransmitter released by most sympathetic postganglionic fibers; also a hormone from the adrenal medulla.

Epinephrine (Adrenaline)

Hormone released by adrenal medulla that augments sympathetic effects such as increased heart rate and blood pressure.

Dopamine

Catecholamine neurotransmitter involved in motor control and reward; chemically related to NE and epinephrine.

Adrenergic Receptors

Alpha or beta receptors on effector cells that bind norepinephrine or epinephrine to produce sympathetic effects.

Acetylcholine (ACh)

Neurotransmitter released by all preganglionic autonomic neurons, parasympathetic postganglionic neurons, and somatic motor neurons.

Splanchnic Nerve

Bundle of autonomic fibers that passes through the sympathetic trunk without synapsing and targets prevertebral ganglia or abdominal organs.

Vagus Nerve (CN X)

Major parasympathetic nerve that decreases heart rate, constricts bronchi, and stimulates GI activity.

Oculomotor Nerve (CN III)

Cranial nerve whose parasympathetic fibers constrict the pupil and adjust lens shape for near vision.

Glossopharyngeal Nerve (CN IX)

Cranial nerve providing parasympathetic fibers that enhance secretion from salivary glands.

Adrenal Medulla

Inner region of the adrenal gland that functions like a sympathetic ganglion, releasing epinephrine and norepinephrine into the blood.

Bronchodilation

Widening of the airway passages, typically mediated by sympathetic stimulation to increase airflow.

Vasoconstriction

Narrowing of blood vessels; sympathetic effect in skin vessels helps conserve heat and raise blood pressure.

Vasodilation

Widening of blood vessels; can occur in coronary and skeletal muscle vessels during sympathetic activation to boost blood flow.

Preganglionic Fiber Exit (T1–L2)

Sympathetic preganglionic axons arise from lateral horns of spinal cord segments T1–L2 and leave via anterior roots.