The Autonomic Nervous System Flashcards

Vocabulary practice flashcards covering key terms, anatomical pathways, neurotransmitters, receptor types, and physiological effects from Chapter 15: The Autonomic Nervous System.

Interoceptors

Sensory receptors located in blood vessels, visceral organs, muscles, and the nervous system that monitor conditions in the internal environment.

Chemoreceptors

Sensory receptors in the autonomic nervous system that monitor the level of blood $CO_2$.

Mechanoreceptors

Sensory receptors in the autonomic nervous system that detect the degree of stretch in the walls of blood vessels and viscera.

Somatic motor neuron pathway

A one-neuron motor pathway in which a single myelinated somatic motor neuron extends from the central nervous system to synapse directly with a skeletal muscle effector using acetylcholine (ACh).

Autonomic motor pathways

Pathways typically consisting of a two-neuron chain (preganglionic and postganglionic neurons) or a preganglionic neuron synapsing with chromaffin cells of the adrenal medulla, targeting glands, cardiac muscle, and smooth muscle.

Preganglionic neuron

An autonomic motor neuron (type B fiber) with its cell body in the central nervous system and an axon extending to an autonomic ganglion.

Postganglionic neuron

An autonomic motor neuron (type C fiber) with an unmyelinated axon extending from an autonomic ganglion to a visceral effector.

Sympathetic nervous system

The division of the autonomic nervous system referred to as the fight-or-flight division, whose stimulation leads to increased alertness and metabolism.

Parasympathetic nervous system

The division of the autonomic nervous system referred to as the rest-and-digest division, whose stimulation slows down most body activity.

Thoracolumbar outflow

The outflow pathway formed by axons of sympathetic preganglionic neurons whose cell bodies are in the lateral gray horns of spinal cord segments T1-L2.

Craniosacral outflow

The outflow pathway formed by axons of parasympathetic preganglionic neurons originating in nuclei of cranial nerves III, VII, IX, and X, and lateral gray matter of spinal cord segments S2-S4.

Sympathetic trunk ganglia

Paired autonomic ganglia that lie in a vertical row on either side of the vertebral column.

Prevertebral ganglia

Sympathetic ganglia located anterior to the vertebral column and close to the large abdominal arteries.

Terminal ganglia

Parasympathetic ganglia typically located near or within the wall of visceral effectors.

White ramus communicans

A structure present in the sympathetic division containing myelinated preganglionic axons that connects a spinal nerve to a sympathetic trunk ganglion.

Gray ramus communicans

A structure present in the sympathetic division containing unmyelinated postganglionic axons that connects a sympathetic trunk ganglion back to a spinal nerve.

Autonomic plexuses

Major networks of autonomic nerve fibers in the abdomen and pelvis, including the celiac, superior mesenteric, inferior mesenteric, renal, and hypogastric plexuses.

Cholinergic neurons

Autonomic neurons that release the neurotransmitter acetylcholine (ACh).

Adrenergic neurons

Autonomic neurons that release the neurotransmitter norepinephrine (NE).

Nicotinic receptors

Cholinergic receptors located on postganglionic neurons, chromaffin cells, and the sarcolemma of skeletal muscle fibers that produce excitation or hormone secretion upon activation.

Muscarinic receptors

Cholinergic receptors located on effectors innervated by parasympathetic postganglionic neurons, sweat glands, and skeletal muscle blood vessels.

$\alpha_1$ adrenergic receptors

Adrenergic receptors located in smooth muscle of blood vessels serving salivary glands, skin, mucosal membranes, kidneys, and abdominal viscera, activation of which causes excitation, vasoconstriction, pupil dilation, and sphincter closure.

$\alpha_2$ adrenergic receptors

Adrenergic receptors located on pancreatic islet beta cells, salivary gland cells, smooth muscle of some blood vessels, and blood platelets, activation of which causes inhibition, decreased insulin secretion, or vasodilation.

$\beta_1$ adrenergic receptors

Adrenergic receptors located in cardiac muscle fibers, juxtaglomerular cells of kidneys, posterior pituitary, and adipose cells, activation of which causes increased force/rate of heart contraction, renin secretion, ADH secretion, and triglyceride breakdown.

$\beta_2$ adrenergic receptors

Adrenergic receptors located in smooth muscle of airways, blood vessels serving heart/skeletal muscle/liver, and visceral organ walls, activation of which causes relaxation, airway dilation, and vasodilation.

$\beta_3$ adrenergic receptors

Adrenergic receptors located in brown adipose tissue that stimulate thermogenesis (heat production).

Neurotransmitters and receptors in ANS divisions

Diagram illustrating that preganglionic neurons release ACh onto nicotinic receptors, while postganglionic neurons release NE (or ACh at sweat glands) in the sympathetic division and ACh onto muscarinic receptors in the parasympathetic division.

Chromaffin cells

Cells of the adrenal medullae innervated by sympathetic preganglionic neurons that release epinephrine and norepinephrine into the blood.

Autonomic reflex arc

A neural circuit composed of a receptor, sensory neuron, integrating center, motor neurons, and effector that regulates visceral functions such as heart rate and blood pressure.

Nervous system homeostatic contributions

The combined actions of nerve impulses and hormones that regulate all major body systems to maintain internal body stability.

Autonomic Dysreflexia

An autonomic nervous system disorder covered in Chapter 15.

Raynaud Phenomenon

An autonomic nervous system disorder covered in Chapter 15.