ANS Essentials

Nervous 3Essentials of the Autonomic

Nervous System

This is not the complete slideshow shown in class, but contains essential points, with audio

The ANS affects the following:

heart rate digestion respiration rate salivation perspiration diameter of the pupils micturition (urination) sexual arousal

Whereas most of its actions are involuntary, some actions of the ANS, such as breathing, work in tandem with the conscious mind.

The ANS is:

Purely motor (though some references include visceral sensory as an arm of the ANS)

A functional, not anatomical, division Opposite is the somatic nervous system

Mostly working beyond our conscious awareness

Autonomic vs. Somatic

A motor neuron within the ANS that lies between the CNS and a ganglion is what type of neuron? Pre-ganglionic - myelinated

A motor neuron within the ANS that lies between a ganglion and an effector is what type of neuron? Ganglionic - unmyelinated

Autonomic vs. Somatic

ANS Divisions

What are the 2 divisions of the ANS? Sympathetic division Parasympathetic division

The parasympathetic division is sometimes referred to as “rest and digest,” but also “craniosacral” because the nerves arise from the brain stem (mainly vagus, CN X) & sacral region

The sympathetic division is sometimes referred to as “thoracolumbar” because of the sympathetic neurons in the spinal nerves of these regions.

Parasympathetic Division

Where are the cell bodies of the preganglionic neurons for the parasympathetic division located? Brainstem S2-S4 (lateral gray matter of spinal cord)


Where are the ganglia of the parasympathetic division found? Terminal ganglia - close to target organ Intramural ganglia - within wall of target organ


The parasympathetic division innervates what structures through the oculomotor nerve? Ciliary muscle Pupillary constrictor of iris

Dilator controlled by sympathetic division


The parasympathetic division innervates what structures through the facial nerve? Submandibular and sublingual glands Lacrimal gland Glands of nasal cavity, mouth, and palate


The parasympathetic division innervates what structures through the glossopharyngeal nerve? Parotid gland


What specific regions of the spinal cord house the cell bodies of the parasympathetic division of the ANS? Lateral horns


What nerves carry fibers of the parasympathetic division of the ANS through the pelvis? Pelvic splanchnic nerves

What does ‘splanchnic’ mean? Visceral

Parasympathetic Effects

Increase saliva production Constrict pupils Constrict airways Produce tears Increase GI motility Contract bladder Erect penis/clitoris

Sympathetic Division

What is another term for the sympathetic division? _____________ division

From what regions of the CNS does the sympathetic division arise? T1-L2 (lateral horns of spinal cord)


What part of spinal nerves do the preganglionic sympathetic axons travel within as they leave the lateral horn of the spinal cord? Anterior root


What sympathetic ganglia lie on the left and right sides of the vertebral column from T1-L2? Sympathetic trunk ganglia

Paravertebral ganglia

What structure of the sympathetic division has the appearance of a pearl necklace? Sympathetic trunk (ganglia and axons)


What clusters of ganglia of the sympathetic division of the ANS lie within the neck? Cervical ganglia

What are the connections between spinal nerves and the sympathetic trunks? Rami communicantes


What structures carry preganglionic sympathetic axons from the T1-L2 spinal nerves to the sympathetic trunk? White rami

What structures carry postganglionic sympathetic axons from the sympathetic trunk to the spinal nerves? Gray rami


What structures are composed of preganglionic axons that do not synapse in a sympathetic trunk ganglion? Splanchnic nerves

Splanchnic nerves of the sympathetic division of the ANS terminate in what structures? Prevertebral (collateral) ganglia


What structures are singular rather than paired, are anterior to the vertebral column, and are located only in the abdominal cavity? Prevertebral ganglia


List the 3 prevertebral ganglia Celiac Superior mesenteric Inferior mesenteric

Sympathetic Pathways

What pathway is a postganglionic axon within if it travels through a gray ramus that is at the same level as the ganglionic neuron to innervate blood vessels or arrector pili muscles or sweat glands? Spinal nerve pathway


What pathway is a postganglionic axon within if the preganglionic neuron synapses with a ganglionic neuron in a sympathetic trunk ganglion, but the postganglionic axon does not leave the trunk via a gray ramus, but instead extends away from the sympathetic trunk ganglion and goes directly to the effector organ? Postganglionic sympathetic nerve pathway


What pathway is a postganglionic axon within if the preganglionic axon passes through the sympathetic trunk ganglia without synapsing and extends to the prevertebral ganglia? Splanchnic nerve pathway


What pathway is a sympathetic axon within if it goes to the adrenal medulla? Adrenal medulla pathway

Sympathetic Effects

Pupil dilation Airway dilation Sweat production Mass activation response to stress

Increased heart rate, blood pressure, breathing rate and depth, dilate pupils, stimulate RAS

Autonomic Nervous System

Usually both divisions of the ANS innervate organs. Where does this dual innervation not occur? Cutaneous region

Includes peripheral blood vessels Sympathetic only

Autonomic Plexuses

What are collections of sympathetic postganglionic axons, parasympathetic preganglionic axons, and some visceral sensory axons? Autonomic plexuses

Autonomic Plexuses

List the 5 autonomic plexuses Cardiac plexus Esophageal plexus Pulmonary plexus Abdominal plexus Hypogastric plexus

CNS Control of ANS

What part of the CNS has the greatest control over the ANS? Hypothalamus

What part of the CNS holds nuclei which have a great deal of influence over autonomic function? Brain stem

CNS Control of ANS

What division of the ANS may process and control certain functions at the level of the spinal cord without involvement of the brain? Parasympathetic

E.g. Defecation and urination

How does the parasympathetic reflex for urination relate to potty training?

The End of Autonomic Nervous System

Education

ANS Essentials