Chapter 16: Autonomic Nervous System Vocabulary

Vocabulary flashcards focusing on key terms, structures, receptor types, and disorders of the Autonomic Nervous System.

Autonomic Nervous System (ANS)

The division of the nervous system that maintains homeostasis by involuntarily regulating the activity of smooth muscle, cardiac muscle, and glands.

Somatic Motor Neuron

A motor neuron with its cell body in the central nervous system and its axon extending directly to innervate skeletal muscle.

Preganglionic Neuron

The first neuron in a two-neuron autonomic series, with its cell body in the CNS and its myelinated axon projecting to an autonomic ganglion.

Postganglionic Neuron

The second neuron in a two-neuron autonomic series, with its cell body located in an autonomic ganglion and its unmyelinated axon extending to the target tissue.

Sympathetic Division

The thoracolumbar division of the ANS, originating from spinal cord levels $T1$ through $L2$, that predominates during physical activity or stress.

Parasympathetic Division

The craniosacral division of the ANS, originating from brainstem nuclei and sacral spinal cord segments $S2$ through $S4$, that predominates during rest.

Sympathetic Chain Ganglia

Connected autonomic ganglia located along the left and right sides of the vertebral column, also referred to as paravertebral ganglia.

Collateral Ganglia

Unpaired sympathetic ganglia located in the abdominopelvic cavity anterior to the vertebral column, also called prevertebral ganglia.

White Ramus Communicans

A short connection between a spinal nerve and a sympathetic chain ganglion containing myelinated preganglionic axons.

Gray Ramus Communicans

A structure containing unmyelinated postganglionic axons that exit a sympathetic chain ganglion to reenter a spinal nerve.

Splanchnic Nerves

Nerves composed of preganglionic sympathetic axons that pass through sympathetic chain ganglia without synapsing and extend to collateral ganglia or the adrenal medulla.

Adrenal Medulla

The inner portion of the adrenal gland composed of specialized cells that secrete approximately $801\%$ epinephrine and $20\%$ norepinephrine into the blood when stimulated.

Terminal Ganglia

Autonomic ganglia of the parasympathetic division located near or embedded within the walls of the target organ.

Autonomic Nerve Plexus

A complex, interconnected neural network formed by sympathetic and parasympathetic neurons along with sensory axons.

Enteric Nervous System (ENS)

A complex network of sensory neurons, motor neurons, and interneurons located within the wall of the digestive tract.

Dual Innervation

The structural arrangement in which an organ receives nerve fibers from both the sympathetic and parasympathetic divisions of the ANS.

Cholinergic Neuron

A neuron that secretes acetylcholine as its neurotransmitter.

Adrenergic Neuron

A neuron that secretes norepinephrine as its neurotransmitter.

Nicotinic Receptors

Cholinergic receptors located on postganglionic neurons in autonomic ganglia and skeletal muscle membranes that cause excitatory responses by opening $\text{Na}^+$ channels.

Muscarinic Receptors

Cholinergic receptors located on cells of parasympathetic effectors and certain sympathetic effectors that produce excitatory or inhibitory responses via G proteins.

Alpha Receptors

A major category of adrenergic receptors (subtypes $\alpha_1$ and $\alpha_2$) located on sympathetic target cells that respond to norepinephrine and epinephrine.

Beta Receptors

A major category of adrenergic receptors (subtypes $\beta_1$, $\beta_2$, and $\beta_3$) located on sympathetic target cells.

Local Reflex

An involuntary reflex operating entirely within the enteric nervous system without central nervous system involvement.

Raynaud Disease

A condition involving spasmodic contraction of blood vessels, particularly in the fingers, caused by exaggerated sensitivity to sympathetic innervation.

Hirschsprung Disease

A functional obstruction in the lower colon and rectum caused by ineffective parasympathetic stimulation and a predominance of sympathetic stimulation.