Chapter 22: Autonomic Nervous System – Vocabulary Flashcards

A set of vocabulary flashcards summarizing key terms and concepts from Chapter 22 on the Autonomic Nervous System.

Autonomic Nervous System (ANS)

The involuntary division of the peripheral nervous system that regulates smooth muscle, cardiac muscle, glands, adipose tissue, and other visceral effectors to maintain homeostasis.

Effectors (ANS)

Target tissues—smooth muscle, cardiac muscle, glands, adipose tissue—controlled by autonomic motor neurons.

Sympathetic Nervous System

Thoracolumbar division of the ANS that produces the ‘fight-or-flight’ response; effects are widespread and long-lasting.

Parasympathetic Nervous System

Craniosacral division of the ANS that promotes ‘rest-and-digest’ functions; effects are localized and short-lived.

Enteric Nervous System

Specialized neural network in the gut that can act autonomously to regulate digestion and interacts with the ANS.

Two-Neuron Pathway

Typical ANS efferent route consisting of a myelinated preganglionic neuron and an unmyelinated postganglionic neuron.

Preganglionic Neuron

First autonomic motor neuron; cell body in CNS, axon myelinated, releases acetylcholine to a ganglion.

Postganglionic Neuron

Second autonomic motor neuron; cell body in a ganglion, axon unmyelinated, innervates the effector.

Ganglion (pl. ganglia)

Cluster of neuron cell bodies located in the peripheral nervous system.

Sympathetic Chain (Sympathetic Trunk)

Series of interconnected sympathetic ganglia alongside the vertebral column where many sympathetic synapses occur.

Thoracolumbar Division

Anatomical description of the sympathetic system—preganglionic cell bodies are in T1–L2 spinal cord segments.

Craniosacral Division

Anatomical description of the parasympathetic system—preganglionic cell bodies in brainstem (CN III, VII, IX, X) and S2–S4 spinal cord.

Dual Innervation

Most visceral organs receive impulses from both sympathetic and parasympathetic divisions for balanced control.

Sympathetic-Only Tissues

Structures that receive exclusive sympathetic input: adrenal glands, sweat glands, and arrector pili muscles.

Adrenal Medulla Direct Innervation

Preganglionic sympathetic fibers synapse directly on adrenal medullary cells, triggering epinephrine release into blood.

Fight-or-Flight Response

Physiological changes (↑ heart rate, bronchodilation, etc.) produced by sympathetic activation during stress or danger.

Rest-and-Digest Response

Physiological state (↓ heart rate, enhanced digestion) promoted by parasympathetic activation during relaxed conditions.

Norepinephrine (Noradrenaline)

Neurotransmitter released by sympathetic postganglionic neurons; binds alpha and beta receptors, producing excitatory or inhibitory effects.

Acetylcholine (ACh)

Neurotransmitter released by all autonomic preganglionic neurons and parasympathetic postganglionic neurons.

Alpha Receptors

Adrenergic receptor subtype on effectors that binds norepinephrine, generally producing excitatory responses.

Beta Receptors

Adrenergic receptor subtype; β₁ on cardiac muscle (excitatory) and β₂ on vascular smooth muscle (inhibitory) respond to norepinephrine.

Nicotinic Receptors

Cholinergic receptors on autonomic ganglionic neurons and skeletal muscle; ACh binding is always excitatory.

Muscarinic Receptors

Cholinergic receptors on parasympathetic effectors; ACh binding may be excitatory or inhibitory (e.g., relaxes bladder wall for urination).

Antagonistic Control

Dynamic balance where sympathetic and parasympathetic divisions exert opposite effects on the same organ to maintain homeostasis.

Homeostasis (ANS)

Stable internal environment maintained by continual sympathetic and parasympathetic signaling to visceral effectors.