Download Comparison of Sympathetic and Parasympathetic Divisions

“ЗАТВЕРДЖЕНО”
на методичній нараді кафедри
нервових хвороб, психіатрії
та медичної психології
“______” _______________ 2008 р.
Протокол № _____
Зав. кафедри нервових хвороб, психіатрії
та медичної психології
професор
В.М. Пашковський
METHODOLOGICAL INSTRUCTION № 11
THEME: AUTONOMIC NERVOUS SYSTEM SYNDROMES OF LESION. METHODS OF
EXAMINATION
Modul 1. General neurology
Сontents modul 2. Pathology of the cranial nerves. The disorders of the autonomic nervous
system and brain cortex functions. Meningeal syndrome. The additional methods of
examination in neurology.
Subject:
Nervous deseases
Year 4
Medical faculty
Hours 2
Author of methodological instructions
MD Filipets O.O.
Chernivtsy 2008
1. Scientific and methodological substantiation of the theme.
The autonomic nervous system is a purely efferent system of nerve fibers with
ganglia and plexuses outside the central nervous system innervating the blood
vessels, heart, viscera, glands, and smooth muscles throughout the body. The
vegetative disturbance have own specific clinical signs.
2. Aim: students should be able to determine independently signs of lesion
Autonomic nervous system, to localize the pathological process (focus) on different
topical levels. Students should be able to formulate and to explain the topical
diagnosis.
Students must know:
1. Anatomical structures and function of the Autonomic nervous system.
2. Specific methods of examination of Autonomic nervous system.
3. The signs of lesion of sympathetic part of vegetative nervous system.
4. The signs of lesion of parasympathetic part of vegetative nervous system.
5. Hypothalamic syndromes.
6. Lesion of limbic-reticular complex.
7. The paroxysmal and permanent disturbances of vegetative function.
Students should be able to:
1.
Examine patient status:
a.
activity of inner organs (attacks of tachy- and bradycardia, breath,
dyspeptic disturbance after meals, abdominal spastic pain, diarrhea,
frequent and abundant urination)
b.
activity of cardiovascular system (attacks of a skin pallor and
hyperemia, high and low of blood pressure)
c.
activity of the sweating, sebaceous glands and lacrimal organs
(salivation, hyperhidrosis, dry skin, eyewatering) etc
d.
activity of pelvic (urogenital) organs (ischuria/retention of urine/,
incontinence of urine and feces)
e.
trophic disturbance (hyperkeratosis, skin lesion, peeling of the
skin, fissures of skin, pustules, skin edema, hyperpigmentation,
alopecia, hemiatrophia)
f.
disturbance of the height and substances exchange (low and high
height, increasing of weight, cachexia, acromegalia)
g.
disturbance of sleep, thermoregulation, memory, emotions and
tendencies
2.
Localize the pathological processes on different levels of somatic
nervous system.
3.
To put topical diagnosis and to explain it.
1.
2.
3.
4.
5.
Student should gain practical skills:
To examine pupillary reaction, eye-heart reflex, solar reflex, vascular responses of
the skin (local and reflex).
To find the difference in blood pressure levels on hands and legs.
To diagnose the pathological processes on different levels of somatic nervous
system.
To examine temperature and activity of sweating (apirine test).
To provide pharmacological tests (atropine, adrenaline, pylocarpine).
4. Integration (basic level).
Subjects
Anatomy
Gained skills
Knowledge of anatomy of sympathetic and
parasympathetic divisions of autonomic nervous
system
Histology
Hystological structure of the sympathetic and
parasympathetic divisions of autonomic nervous
system
Physiology
Knowledge of function of vegetative reflex arch .
Subject
Unlike the somatic nervous system, which senses and responds to changes in
the external world, the visceral nervous system senses and responds to changes within
the environment inside the body. The primary function of the visceral nervous system
is to maintain the internal environment within physiological limits (homeostasis).
Most visceral regulation is achieved via reflexes at subconscious levels. Components
of the visceral nervous system exist at all levels of the neuraxis (forebrain, midbrain,
hindbrain, spinal cord, and periphery) and they regulate the function of smooth
muscle, cardiac muscle, and glands. To control these effectors, the visceral system
uses both neural and humoral (hormones released into the blood) mechanisms.
In addition to neurohumoral differences with the somatic nervous system, the
visceral nervous system has two other unique characteristics. First, the effector
mechanisms are still capable of functioning in the absence of neural control. For
example, cardiac muscle continues to contract rhythmically in the absence of neural
innervations. Second, the peripheral level of the visceral nervous system contains
ganglia that play an important part in the reflex control of effector function. Visceral
ganglia are organized into two systems. The paravertebral ganglia form a chain
located immediately adjacent to the vertebral column that extends the entire length of
the spinal cord and functions in the sympathetic division of the visceral efferent
system. The parasympathetic division of the visceral efferent system contains
peripheral ganglia that are located in or around the effector mechanism that they
innervate.
Visceral Afferent System
The two primary types of visceral receptors, mechanoreceptors and
chemoreceptors, are distributed throughout the body. Mechanoreceptors sense
pressure, stretch, or tension. Slow-adapting mechanoreceptors sense fullness in the
bowel, bladder, and stomach. Fast-adapting mechanoreceptors sense the movement
in the lungs and arteries. The second receptor type, chemoreceptors, exist only in
the visceral nervous system. Chemoreceptors sense taste and smell as well as the
concentration of hydrogen ions (pH) in the stomach and partial pressure of oxygen and
carbon dioxide in the blood. Chemoreceptors located in the hypothalamus and
reticular formation respond to the levels of blood sugar and electrolytes. These
receptors help the hypothalamus to regulate hunger and thirst.
Visceral afferent fibers are small-diameter, myelinated and unmyelinated
axons that exhibit slow conduction velocity. Some first-order visceral afferent fibers
project only as far as the peripheral ganglia while others project into the spinal cord
and brain stem, and ascend to higher levels of the brain. Two pathways exist for
peripheral afferent fibers. They either join with peripheral and spinal nerves to
project directly into the spinal cord or they follow blood vessels centrally until
reaching a ganglion. The fibers that project to ganglia may either synapse and
terminate, pass through the ganglion giving off a collateral synapse, or pass directly
through the ganglion and enter the central nervous system (CNS). Visceral afferent
fibers that enter the central nervous system have their cell bodies located in the
dorsal root ganglia or the sensory portion of a cranial nerve nucleus. To enter the
spinal cord, visceral afferent fibers join spinal nerves by projecting through the
ganglion and white ramus communicans (communicating branches that are white
because they are myelinated) and enter the spinal cord along with the other fibers of
the dorsal root. In the brain stem, fibers project directly to cranial nerve nuclei.
The visceral afferent fibers that enter the central nervous system establish
multiple synaptic connections at the level of entry. They synapse with both visceral
and somatic efferent neurons. Synaptic connections with visceral neurons form the
anatomical basis for central visceral reflexes. Synaptic connections with somatic
neurons form the basis for associated somatic and visceral behaviors such as the
postural collapse that often accompanies severe visceral pain. The convergence of
visceral and somatic fibers onto a postsynaptic neuronforms the anatomical basis of
referred pain. Referred pain originates from a deep visceral organ (heart, appendix,
etc.) but is "referred" to more superficial areas of the body with the same segmental
representation in the spinal cord. Visceral afferent information ascends in the spinal
cord and brain stem via the lateral spino-thalamic tract and dorsal columns to the
reticular formation and then up to the hypothalamus, thalamus, and cerebral cortex.
In spite of cortical projections, the primary destination of visceral afferent
activity is the hypothalamus. The hypothalamus is the integrator of visceral
information that it receives from the periphery, spinal cord, reticular formation,
thalamus, and rhinencephalon. The visceral nervous system contains large numbers
of afferent fibers (the vagus nerve contains approximately 80 percent afferent fibers),
but conscious perception of visceral sensations is limited to the stomach, bowel, and
bladder under normal circumstances. Most visceral function is controlled by
subcortical reflexes, which makes diagnosis and localization of visceral dysfunction
extremely difficult.
Visceral Efferent System
The visceral nervous system exerts control over smooth muscle, cardiac muscle,
and glands via three pathways: sympathetic, parasympathetic, and humoral. Together,
the sympathetic and parasympathetic pathways comprise the autonomic nervous
system. Both these divisions are two-neuron systems and consist entirely of efferent
fibers.
The Sympathetic Division. The sympathetic division has components in the
hypothalamus, reticular formation, spinal cord, and periphery. It assumes
responsibility for the control of activating types of behavior, such as dilation of the
pupil, increased heart rate and respiratory rate, and the shunting of blood to the
peripheral musculature, all of which prepare the body to respond to stress. Descending
fibers from the hypothalamus and reticular formation are located in the lateral brain
stem and spinal cord. The cell bodies of preganglionic sympathetic neurons are
located in the lateral horn of the gray matter in the first thoracic through third
lumbar segments of the spinal cord (T1-L3). Anatomically, the sympathetic division is
referred to as the thoracolumbar division of the autonomic nervous system. Short
preganglionic fibers exit the spinal cord via the ventral root and project to the
paravertebral ganglia via the white rami communicantes. The white ramus is so
colored because preganglionic sympathetic fibers are myelinated.
Once inside the paravertebral ganglion chain (which extends from the first
cervical vertebra to the coccyx), preganglionic fibers project in one of three ways.
They may synapse immediately with postganglionic fibers, ascend or descend within
the ganglion chain before synapsing with postganglionic fibers, or pass through the
paravertebral ganglia without synapsing. These direct projecting fibers are
myelinated and form the three splanchnic nerves (superior, inferior, and lowest)
that synapse in the prevertebral ganglia (ciliac, superior mesencephalic, and inferior
mesencephalic). Before synapsing, single preganglionic fibers diverge extensively to
form synaptic connection with as many as 10 postganglionic neurons, which
distribute sympathetic stimulation widely throughout the body. Long unmyelinated
postganglionic fibers exit the ganglia via the gray rami communicantes and provide
the sympathetic innervation to effector mechanisms. Postganglionic fibers join with
peripheral nerves and project directly to effectors.
Preganglionic sympathetic fibers produce shortlived facilitation of
postganglionic neurons by using acetylcholine neurotransmitter substance.
Postganglionic fibers produce long-lived, generalized, and specific activation of
effector mechanisms by using norepinephrine neurotransmitter substance. Based on
the transmitter substance used, most preganglionic fibers are classified as
cholinergic and most postganglionic fibers as adrenergic (sweat glands and blood
vessels in skeletal muscle are exceptions).
The Parasympathetic Division. The parasympathetic division of the
autonomic nervous system arises from the brain stem and sacral segments of the
neuraxis and is therefore referred to as the craniosacral division. This division
assumes responsibility for regulating restorative types of behavior, including
eating, sleeping, and digestion. Stimulation of parasympathetic fibers increases
digestion and the absorption of nutrients, drainage of the bowel and bladder,
decrease of heart rate and respiratory rate, and shunting of blood to the digestive
system from the musculoskeletal system.
Parasympathetic ganglia are located distal to the central nervous system in or
near the effector mechanism. Thus, preganglionic fibers are long and
postganglionic fibers are short. Both preganglionic and postganglionic fibers of the
parasympathetic division produce specific, short-lived effects on postsynaptic
membranes by using acetylcholine neurotransmitter substance. The entire
parasympathetic division is classified as a cholinergic system.
Long preganglionic fibers from cranial segments exit the central nervous
system with efferent fibers from the oculomotor (III), facial (VII), glossopharyn-geal
(IX), and vagus (X) cranial nerves. Oculomotor, facial, and glossopharyngeal nerves
innervate structures in the head and throat. Parasympathetic ganglia in the head
region are discrete constellations of neurons, smaller than the head of a pin. The
ciliary ganglion is located just behind the eyeball and helps regulate the shape of the
lens and diameter of both the lens and the pupil. The sphenopalatine ganglion is
found in the lateral wall of the nasal cavity near the nasopharynx and helps to
regulate the glands of the eye and nasal and oral cavities. The submandibular
ganglion is located inside the jaw and helps to regulate parotid (salivary) glands.
The optic ganglion is found just inside the mandible, beneath the temporal bone,
and helps regulate sublingual and submaxillary (salivary) glands. The vagus nerve
contains approximately 75 percent of all parasympathetic outflow from the cranial
region. The vagus nerve provides the parasympathetic innervations to the organs of
the thorax and abdomen.
An increase in the parasympathetic activation from the sacral region
stimulates digestion and excretion. In the second, third, and fourth sacral regions
(S2, S3, S4), the cell bodies of preganglionic fibers are located in the lateral region of
the ventral horn. The sacral outflow provides the parasympathetic innervation to the
urinary system, lower colon, anal sphincter, and reproductive system.
Preganglionic fibers exit the spinal cord via the ventral roots and project in the
pelvic nerve to synapse with postganglionic parasympathetic neurons in the pelvic
ganglion plexus. Postganglionic parasympathetic neurons innervate the descending
colon, bladder, and external genitalia.
Table 1 compares the sympathetic and parasympathetic divisions.
Table 1.
Comparison of Sympathetic and Parasympathetic Divisions
Component
Sympathetic
Parasympathetic
CNS segments of origin
Thoracic-lumbar region of the spinal cord
Cranial-sacral regions of the spinal cord
Location of ganglia
Paravertebral ganglion chain
On or near effector organ
Preganglionic neuron
Short, myelinated
Long, myelinated
Preganglionic neurotransmitter
substance
Postganglionic neuron
Acetylcholine
Long, unmyelinated
Postganglionic neurotransmitter Norepinephrine
substance
Acetylcholine
Short, unmyelinated
Acetylcholine
Divergence ratio
1:10
1:3
Outflow specificity
Can be widespread
Can be specific
Specific
Behavior produced with
stimulation
"Fight or flight"
Sedentary activities
Voiding
Effect on energy stores
Energy mobilization
Energy utilization
Inhibition of digestion
Energy conservation
Energy restoration
Stimulation of digestion
The Enteric Division
The enteric division is concerned with control of the gastrointestinal tract,
pancreas, and gallbladder. Because these structures contain sensory receptors, afferent neurons, peripheral ganglia, and efferent neurons, their control is sometimes
referred to as the enteric nervous system. Although the enteric nervous system is
capable of functioning independently, its activity is normally regulated by CNS
reflexes. Because of its role in controlling digestion, the enteric division plays a
major part in homeostasis. The neurons of the enteric division are arranged in
complex interconnecting plexuses of ganglia and nerve fibers located between the
layers of muscle and endothelium. Extrinsic innervation of the enteric division is
supplied by both the sympathetic and parasympathetic systems. Sympathetic
innervation consists primarily of postganglionic fibers from the cervical paravertebral
chain. These fibers project to ganglia in the wall of the stomach, small intestine, and
colon. Parasympathetic preganglionic fibers project directly to enteric ganglia in the
stomach, colon, and rectum through the vagus and pelvic splanchnic nerves.
Autonomic innervation, both sympathetic and parasympathetic, provides a second
level of control of digestion that is capable of overriding intrinsic enteric control in
situations of emergency and stress.
Central Visceral Control.
The central control of the visceral nervous system includes three primary
areas: the cerebral cortex, hypothalamus, and reticular formation. In the visceral
nervous system, cortical centers play a minor role in central control. The two
cortical centers, the ventrobasal frontal lobe and the rhinencephalic cortex (medial
surface of frontal and temporal lobes), function mainly to integrate somatic and
visceral information. Efferent pathways from these areas project directly to the
hypothalamus, mamillary bodies, and brain stem reticular formation. There are no
direct projections into the spinal cord. Cortical centers coordinate emotional and
visceral reactions such as blushing, which is associated with embarrassing situations.
The visceral cortex is part of the larger limbic system, which regulates most human
emotions and their associated visceral reactions. Limbic and visceral structures are
commonly involved in emotional disorders.
The hypothalamus is the major region of central visceral control. All visceral
sensory information is projected to the hypothalamus and the hypothalamus has
efferent projections to other visceral and limbic areas of the cortex, reticular
formation, and spinal cord. Both afferent and efferent visceral pathways are diffusely
organized. The hypothalamus has primary responsibility for regulating restorative
and preparatory behavior as well as homeostasis. The anterior hypothalamus controls
the posterior hypophysis and parasympathetic system, which regulate restorative
types of behavior. The posterior hypothalamus controls the adenohypophysis and
sympathetic system, which regulate preparatory types of behavior. The
medioventral hypothalamus uses the neurohypophysis to regulate homeostasis.
The reticular formation, the remaining area of importance in the central control
of the visceral system, is among the oldest structures in the mammalian brain. It
extends from the midbrain through the brain stem and consists of numerous centers
that control specific, visceral, life-support functions such as heart and respiratory
rates. Reticular centers are not discrete nuclei but, rather, clusters of cells that
regulate specific visceral function.
Opposing Mechanisms or Functional Synergy.
Most visceral effector organs receive innervation from both postganglionic
sympathetic and parasympathetic fibers. Sympathetic neurotransmitter substances
(epi-nephrine and norepinephrine) tend to increase effector function while
parasympathetic neurotransmitter substance (acetylcholine) tends to decrease effector
function. Both types of efferent fibers are tonically active. Thus, the level of activity
of visceral effector organs is determined by the dynamic equilibrium between
sympathetic and parasympathetic stimulation. For example, norepinephrine released
from postganglionic sympathetic fibers acts on cardiac muscle to increase heart rate
and contractility, whereas activation of postganglionic parasympathetic fibers in the
vagus nerve causes the release of acetylcholine, which profoundly decreases heart
rate and contractility, thereby decreasing cardiac output. Thus, adaptive responses
are executed or homeostasis is maintained by varying autonomic drive (sympathetic
or parasympathetic) of visceral organs in proportion to external challenges to the
system.
Limbic system.
The components of the limbic system are restricted to the forebrain, and
midbrain. The limbic system controls emotions (drive, motivations) and affect.
Because of the prominent visceral component in each of this types of behavior, the
function of the limbic system is inextricably linked with that of the visceral nervous
system, and is therefore sometimes referred to as the “visceral brain”.Limbic
structures include the hippocampus, fornix, mamillary bodies, anterior nucleus of
thalamus, and cingulated gyrus, as well as regions of temporal, parietal, and frontal
lobes.
Clinical Aspects.
High blood pressure, or hypertension, is the most common health problem
associated with the cardiovascular system. Hypertension leads to cerebrovascular
accidents, heart attacks, and kidney failure, which kill tens of millions of people
every year. Hypertension has many causes; however, increased sympathetic drive is
one important factor in the development and maintenance of high blood pressure.
Sympathetic stimulation increases both cardiac output and peripheral vascular
resistance, the two leading determinants of blood pressure. Antihypertensive
drugs lower blood pressure by decreasing sympathetic drive. Beta-adrenergic
blocking agents reduce the sympathetic drive to the heart, thereby reducing cardiac
output. Alpha-adrenergic blocking agents reduce peripheral vascular resistance by
interfering with the vasoconstriction produced by the norepinephrine released from
sympathetic fibers.
Autonomic dysreflexia or sympathetic hyperreflexia is a specific type of
hypertension found in individuals with spinal cord lesions above T7. An abnormal
sympathetic response to bladder or bowel distention or painful stimuli in the viscera
produces dangerous increases in blood pressure, headache, perspiration, and chills.
This response is not self-limiting and is therefore potentially life threatening.
Postural hypotension is a less dangerous though more common blood pressure
abnormality. Postural or orthostatic hypotension (low blood pressure) produces lightheadedness or fainting after rising from a recumbent or sitting position. The
condition results from a failure of the visceral nervous system in sensing and
responding adaptively to the change in blood pressure. As the person stands up,
gravity pulls the blood into the lower extremities. Unless the tension in the
vasculature of the lower extremities is increased proportionately, blood will pool in the
legs, perfusion of the brain will drop, and consciousness will be lost. The
baroreceptor reflex normally senses and responds automatically to changes in aortic
blood pressure in order to maintain blood flow to the brain. The exact cause of
postural hypotension, pressure receptors, afferent transmission, CNS integration,
peripheral sympathetic or parasympathetic efferents, or effector response to
stimulation remains unknown.
Diabetes mellitus produces widespread problems throughout the body,
including peripheral neuropathy involving both somatic and visceral neurons. Smalldiameter neurons, both myelinated and unmyelinated, are the most vulnerable. The
clinical symptoms of autonomic diabetic neuropathy often include cardiovascular
control and gastrointestinal motility. The inability to produce and utilize adequate
amounts of insulin causes metabolic breakdown and loss of function in the neurons
that control these functions.
The papillary reaction. Normally the pupils are round and equal in diameter.
Normal pupils are small in sleep and dilate with arousal. Difference in size
(anisocoria), if small, may not represent disease and can be evaluated accurately only
with reference to other findings, such as ptosis. The large pupil may react poorly to
light as a result of a partial third-nerve paralysis, or the smaller pupil may be part of
Horner’s syndrome.
Horner’s syndrome, when complete, is characterized by:
 ptosis of the upper lid
 miosis
 loss of sweating on the same side of the face
 papillary reaction to light is normal, but the pupil does not dilate to
psychosensory stimuli such as a loud noise.
The Argyll Robertson pupils of tabetic neurosyphilis are small (miotic),
irregular, an often unequal in size. They react little or not at all to light but constrict
promptly when the eyes converge on a near object. A similar dissociation between
the light reaction and the near response may be seen in patient with diabetes,
encephalitis, and midbrain neoplasm.
The disturbance of vegetative function
The paroxysmal signs
The disturbance of vegetative functions :
1.The paroxysmal signs
Sympathy-adrenal attacks:
Vagoinsular attacks:
a) skin pail
a) hyperemia
b) xerostomia
b) hyperhidrosis
c) dryness of hair and skin
c) oily skin and hair
d) tachycardia
d) bradycardia
e) high blood pressure
e) low blood pressure
f) midriasis and widing of Eye-slit
f) miosis
g) exophthalmia
g) angina pectoris
h) tremor
h) salivation
i) gooseflesh
i) breathlessness
j)abdominal spastic pain
k) diarrhea
l)frequent and abundant urination
2.The lesion (permanent) signs:
a) periarthritis
a) incontinence of urine and feces
b) epicondilitis
b) ischuria/retention of urine
c) miositis
c) eye accommodation paralysis
d) hyperkeratosis
d) midriasis
e) fissures of skin
e) dyspnea
f) arthropatias
f) apnea
g) tropic ulcer
g) cardiac arrhythmia
h) alopecia
h) asystolia
i) hyperpigmentation
i) collapse
j) Horner’s sign (ptosis, miosis,
enophthalmia)
Self assessment:
Tests for self-assessment:
1. Clinical features of sympathy-adrenal attack.
2. Clinical features of vago-insular attack.
3. Enumerate hypothalamic syndromes.
4. Name the symptoms of lesion of limbic-reticular complex.
5. Describe vegetative-trophic disorders in case of lateral horns of spinal cord
lesion.
6. Describe the irritation symptoms of sympathetic nerve of vertebral artery.
7. Enumerate hypothalamic realizing-factors.
8. Enumerate hypothalamic inhibits factors.
Tests
1. What makes a part of suprasegmental division of autonomic nervous system
a) truncus simpaticus;
b) Nucleus ruber;
c) hypothalamus;
d) septum pellucidum;
e) substantia nigra.
2.
a)
b)
c)
d)
e)
Sympathetic fibers from the cerebrospinal center innervate:
M. ciliaris;
M. Sphincter pupillae;
M. Dilatator pupillae;
M. Rectus medialis;
M. Obliquus superior.
3.
a)
b)
c)
d)
e)
In what time after skin irritation red vessel reaction appears
1-5 seconds;
5-11 seconds;
20-30 seconds;
25-35 seconds;
30-40 seconds.
Real-life situations:
1. Patient has prosoplegia, xerophtalmia, ageysia of anterior 2/3 of tongue.
What vegetative structures are damaged?
2. Patient with spastic paraplegia of lower extremities has centrally
uninhibited bladder. What part of nervous system is damaged
References:
1.
Basic Neurology. Second Edition. John Gilroy, M.D. Pergamon press.
McGraw Hill international editions, medical series. – 1990.
2.
Clinical examinations in neurology /Mayo clinic and Mayo foundation. – 4th
edition. –W.B.Saunders Company, Philadelphia, London, Toronto. – 1976.
3.
McKeough, D.Michael. The coloring review of neuroscience /D.Michael
McKeough/ - 2nd ed. – 1995.
4.
Neurology for the house officer. – 3th edition. – howard L.Weiner, MD and
Lawrence P. Levitt, MD, - Williams&Wilkins. – Baltimore. – London. –
1980.
5.
Neurology in lectures. Shkrobot S.I., Hara I.I. Ternopil. – 2008.
6.
Van Allen’s Pictorial Manual of Neurologic Tests. – Robert L. Rodnitzky. 3th edition. – Year Book Medical Publishers, inc.Chicago London Boca
Raton. - 1981.