Access over 20 million homework & study documents

Ans notes

Content type
User Generated
Rating
Showing Page:
1/10
Autonomic Nervous System
Overview
The autonomic nervous system is a very complex multifaceted neural network that maintains
internal physiologic homeostasis. This network includes cardiovascular, thermoregulatory,
gastrointestinal (GI), genitourinary (GU), and ophthalmologic (pupillary) systems. Given the
complex nature of this system, a stepwise approach to autonomic disorders is required for
proper understanding.
The goal for this chapter remains focused at step III on the anatomy of the autonomic nervous
system.
Step I: Understand the reason for testing
Step II: Recognition and etiology (especially small fiber neuropathy)
Step III: Understand basic anatomy and neurophysiology
Step IV: Learn the methods for testing
Step V: Diagnosis and management
Almost 10% of the population (or over 30 million people in the United States) may acquire
an autonomic disorder requiring medical attention. The autonomic nervous system is a
versatile neural network maintaining internal physiologic homeostasis. Disorders of
autonomic nervous system can be present with both central as well as peripheral nervous
system localization.
The image below depicts the autonomic nervous system.
Autonomic nervous system.
The etiology of autonomic dysfunction can be primary or idiopathic and secondary causes.
Autonomic failure is seen in multiple system atrophy, pure or progressive autonomic failure,
Parkinson and other neurodegenerative diseases, metabolic diseases such as Wernicke and
cobalamin deficiency, diabetes mellitus, hyperlipidemia, trauma, vascular diseases, neoplastic
diseases, and multiple sclerosis. In addition, autonomic dysfunction is associated with various
medications.
In addition to diabetes, autonomic dysfunction is associated with other neuropathies,
including Guillain-Barr é syndrome, Lyme disease, HIV infection, leprosy, acute idiopathic
dysautonomia, amyloidosis, porphyria, uremia, and alcoholism. Besides nerve localization in

Sign up to view the full document!

lock_open Sign Up
Showing Page:
2/10
the peripheral nervous system, it occurs in diseases of the presynaptic neuromuscular junction
such as botulism and myasthenic syndrome.
In addition to the acquired causes, inherited disorders like hereditary sensory-autonomic
neuropathy (HSAN), familial amyloid polyneuropathy (FAP), Tangier disease, and Fabry
disease also exist.
Clinically, postural lightheadedness, dry mouth, dry eyes, impotence, loss of sweating or
hyperthermia, nocturnal diarrhea, gastroparesis, impaired accommodation, urinary or bowel
incontinence, and small fiber neuropathy (SFN) are some of the presenting symptoms. Most
peripheral neuropathies affect all fiber sizes. Few peripheral neuropathies are associated with
pure or predominantly small-fiber involvement. A large proportion are associated with
diabetes. Painful burning feet is caused by a sensory neuropathy with small-fiber involvement
in more than 90% of cases. Patients with pure small-fiber involvement display normal large
fiber function. Muscle bulk, strength, muscle stretch reflexes, and large fiber sensory function
(ie, vibration, proprioception) are normal.
Small fibers are both myelinated and unmyelinated. Small myelinated fibers transmit
preganglionic autonomic efferents (B fibers) and somatic afferents (A delta fibers).
Unmyelinated (C) fibers transmit postganglionic autonomic efferents as well as somatic and
autonomic afferents. Both A delta and C fibers are widely distributed in skin and deep
tissues. The neurotransmitter for preganglionic sympathetic and parasympathetic nervous
system as well as postganglionic parasympathetic nervous system is acetylcholine. The
neurotransmitter for the postganglionic sympathetic nervous system (innervating sweat
glands) is acetylcholine, whereas remaining postganglionic sympathetic nervous system is
norepinephrine.
Electromyography plays a key role in the evaluation of most peripheral neuropathies and
helps in assessing only large myelinated fibers. Thus, pure SFNs may be associated with
normal findings on routine electro-physiologic studies. Elderly patients who lack sural
sensory responses can still be diagnosed with small-fiber neuropathy. Patients with symptoms
other than neuropathic certainly need autonomic function testing for appropriate diagnosis.
Gross Anatomy
Central integration
The central autonomic network is a complex network in the central nervous system
integrating and regulating autonomic function. The network involves cerebral cortex (the
insular and medial prefrontal regions), amygdala, stria terminalis, hypothalamus, and
brainstem centers (periaqueductal gray, parabrachial pons, nucleus of the tractus solitarius,
and intermediate reticular zone of the medulla).
[1]
Efferent pathways
The autonomic nervous system consists of the sympathetic and parasympathetic nervous
system. The sympathetic nervous system descends to the intermediolateral and
intermediomedial cells in the thoracolumbar regions of the spine, extending from TI to L2.
Preganglionic axons exiting the spinal cord enter the white rami communicantes to join a
network of prevertebral and paravertebral ganglia. They are relatively short, myelinated, and

Sign up to view the full document!

lock_open Sign Up
Showing Page:
3/10

Sign up to view the full document!

lock_open Sign Up
End of Preview - Want to read all 10 pages?
Access Now
Unformatted Attachment Preview
Autonomic Nervous System Overview The autonomic nervous system is a very complex multifaceted neural network that maintains internal physiologic homeostasis. This network includes cardiovascular, thermoregulatory, gastrointestinal (GI), genitourinary (GU), and ophthalmologic (pupillary) systems. Given the complex nature of this system, a stepwise approach to autonomic disorders is required for proper understanding. The goal for this chapter remains focused at step III on the anatomy of the autonomic nervous system. • • • • • Step I: Understand the reason for testing Step II: Recognition and etiology (especially small fiber neuropathy) Step III: Understand basic anatomy and neurophysiology Step IV: Learn the methods for testing Step V: Diagnosis and management Almost 10% of the population (or over 30 million people in the United States) may acquire an autonomic disorder requiring medical attention. The autonomic nervous system is a versatile neural network maintaining internal physiologic homeostasis. Disorders of autonomic nervous system can be present with both central as well as peripheral nervous system localization. The image below depicts the autonomic nervous system. Autonomic nervous system. The etiology of autonomic dysfunction can be primary or idiopathic and secondary causes. Autonomic failure is seen in multiple system atrophy, pure or progressive autonomic failure, Parkinson and other neurodegenerative diseases, metabolic diseases such as Wernicke and ...
Purchase document to see full attachment
User generated content is uploaded by users for the purposes of learning and should be used following Studypool's honor code & terms of service.

Anonymous
Just what I was looking for! Super helpful.

Studypool
4.7
Indeed
4.5
Sitejabber
4.4

Similar Documents