Autonomic Nervous System

Flashcards covering key vocabulary terms related to the Autonomic Nervous System, its divisions, neurons, neurotransmitters, and receptors.

Autonomic Nervous System (ANS)

Consists of motor neurons that innervate smooth muscles, cardiac muscle, and glands; makes adjustments for optimal body activities; operates via subconscious control.

Involuntary Nervous System

Another name for the Autonomic Nervous System, indicating its subconscious control over body functions.

General Visceral Motor System

Another name for the Autonomic Nervous System, emphasizing its control over visceral (internal) organs.

Somatic Motor Neurons

Have cell bodies in the spinal cord and a single neuron traveling from the spinal cord to skeletal muscle effectors.

Autonomic Motor System

Has two sets of neurons in the PNS: a preganglionic neuron with its cell body in the brain/spinal cord, and a postganglionic neuron with its cell body in an autonomic ganglion.

Preganglionic Neuron

The first neuron in the ANS two-neuron chain; its cell body resides in the brain stem or spinal cord, and its axon synapses with the second neuron at a ganglion.

Postganglionic (Ganglionic) Neuron

The second motor neuron in the ANS two-neuron chain; its cell body synapses with the preganglionic axon at an autonomic ganglion, and its axon extends to the effector organ.

Denervation Hypersensitivity

When a visceral effector organ becomes even more sensitive to stimulation if a nerve is cut, unlike skeletal muscle which atrophies.

Parasympathetic Division

A division of the ANS that promotes maintenance functions and conserves energy, often called the 'rest-and-digest' system.

Sympathetic Division

A division of the ANS that mobilizes the body during activity, often referred to as the 'fight-or-flight' system.

Dual Innervation

The condition where most visceral organs are served by both the sympathetic and parasympathetic divisions, allowing them to counterbalance each other.

Fight-or-Flight System

The sympathetic division is known by this name because it prepares the body for stressful situations, increasing heart rate, shunting blood, and releasing glucose.

Thoracolumbar Division

Refers to the sympathetic division because its preganglionic neurons originate from the thoracic and lumbar regions of the spinal cord.

Paravertebral Ganglia (Sympathetic Chain Ganglia)

Ganglia that run parallel to the spinal cord where sympathetic postganglionic neurons synapse.

Collateral (Paravertebral) Ganglia

Sympathetic ganglia located anterior to the vertebral column, such as the celiac, superior mesenteric, and inferior mesenteric ganglia, where splanchnic nerves synapse.

Splanchnic Nerves

Formed by sympathetic neurons that exit the spinal cord below the diaphragm and do not synapse in the sympathetic chain, instead synapsing in collateral ganglia.

Rest-and-Digest System

The parasympathetic division is known by this name because it promotes activities like digestion, diuresis, and defecation while conserving energy.

Craniosacral Division

Refers to the parasympathetic division because its preganglionic neurons come from the brain (via cranial nerves) or the sacral region of the spinal cord.

Terminal Ganglia

Ganglia where parasympathetic preganglionic fibers synapse with postganglionic neurons; they are located close to or within target organs.

Acetylcholine (ACh)

A major neurotransmitter of the ANS; released by cholinergic fibers at all ANS preganglionic axons and all parasympathetic postganglionic axons.

Norepinephrine (NE)

A major neurotransmitter of the ANS; released by adrenergic fibers at almost all sympathetic postganglionic axons (except those at sweat glands).

Cholinergic Fibers

Axons that release the neurotransmitter Acetylcholine (ACh).

Adrenergic Fibers

Axons that release the neurotransmitter Norepinephrine (NE).

Cholinergic Receptors

Receptors that bind to Acetylcholine (ACh); include nicotinic and muscarinic types.

Nicotinic Receptors

A type of cholinergic receptor stimulated by ACh from preganglionic neurons, found on all postganglionic neurons and adrenal medullary cells.

Muscarinic Receptors

A type of cholinergic receptor stimulated by ACh released from postganglionic neurons; their effect can be inhibitory or excitatory depending on the target organ.

Adrenergic Receptors

Receptors that respond to Norepinephrine (NE) or epinephrine; divided into alpha (α) and beta (β) classes.

Alpha (α) Receptors

A class of adrenergic receptors sensitive to norepinephrine, with subclasses α1 and α2; generally cause constriction of blood vessels and visceral organ sphincters.

Beta (β) Receptors

A class of adrenergic receptors sensitive to epinephrine, with subclasses β1, β2, and β3; generally increase heart rate (β1) or cause dilation of blood vessels and bronchioles (β2).

Basal Sympathetic and Parasympathetic Tone

The state where both ANS divisions are partially active, contributing to the resting activity of most visceral organs.