Amanda Hess Borzacchini
2nd year, 1st semester
The vegetative nervous system controls the
activity of all organs concerned with the
vegetative function of the body
circulation, reproduction, excretion, nutrition)
and accomplishes trophic innervation.
The trophic function of the vegetative nervous
system is responsible for the nutrition of the
tissues and organs in conformity to their
functioning under certain environmental
conditions (adaptational-trophic function).
The vegetative nervous system is separated into
two systems: the sympathetic and
The sympathetic system is mainly concerned
with trophic functions. It is responsible for
nutrient consumption, intensification of oxidation
processes, respiration and increases the rate of
cardiac activity and supply of oxygen to the
The parasympathetic system carries a protective
role, like constriction of the pupil in bright
light, inhibition of cardiac activity, evacuation of
the cavitary organs.
Comparison of the areas of distribution of the
sympathetic and parasympathetic innervation discloses.
Firstly some organs have the predominant role of one
vegetative part over the other; e.g.: the urinary bladder
receive mostly parasympathetic innervation and the
sweat glands, the spleen, suprarenals are supplied only
with the sympathetic innervation.
Secondly, in organs with double innervation, the
interaction of the sympathetic and parasympathetic
nerves are antagonistic; e.g.: the stimulation of
sympathetic nerves causes dilatation of the
pupil, constriction of the vessels, increase in the rate of
the cardiac Contractions; in contrast, the stimulation of
parasympathetic nerves leads to constriction of the
pupil, dilatation of the vessels, decrease in the rate of
The antagonism of the sympathetic and
parasympathetic system are reciprocally
affected, the relations between them alter
dynamically in the different phases of the
functioning of this or that organ; they can
act both as antagonists and as synergists.
The normal function of our organism is
ensured by the coordination and regulation
brought by the cerebral cortex. The
sympathetic and parasympathetic are
distinguished in the vegetative system
according to the physiological and
The sympathetic nervous system
The central part of the sympathetic
system is located in the lateral horns of
the spinal cord between the level of C7
and Th1-L3 in the intermediolateral
It give rise to fibres innervating the
smooth muscles of the viscera and the
sensory organs (eyes), and the glands.
Vasomotor, pilomotor and respiration
centres are also located here.
The peripheral part of
the sympathetic system
is formed by two
symmetrical right and
left sympathetic trunks
stretching on either
side of the spinal from
the base of the skull to
the coccyx where the
caudal ends of both
trunks meet to form a
Each sympathetic trunk is composed of a
series of nerve ganglia of the first order
connected by longitudinal interganglionic
branches that consist of nerve fibres.
The processes of cells located in the
lateral horns of the thoracolumbar part of
the spinal cord emerge from it through the
anterior roots and pass in the white
communicating branches to the
From the white communicating branches the
processes of the cells join by means of synapsis
with the cells of the sympathetic trunk ganglia or
pass through the ganglia without interruption and
reach one of intermediate ganglia. This is the
From the ganglia of the sympathetic trunk or
from the intermediate ganglia arise non-
medullated fibres of the postganglionic
pathways and pass to the blood vessels and
The sympathetic system has a somatic part, it is
connected with the spinal nerves providing
innervation of the soma. This connection is
brought about by the grey communicating
branches which are segment of postganglionic
fibres stretching from the sympathetic trunk
ganglia to a spinal nerve.
As components of the grey communicating
branches and spinal nerves the postganglionic
fibres spread in the vessels, glands, and smooth
muscles of the skin of the trunk and limbs, as
well as in the striated muscles for whose nutrition
and tonus they are responsible.
Thus, the SNS is connected with the
somatic system by two types of
communicating branches, white and grey.
The white communicating branch
(medullated) are the preganglionic fibres;
they stretch from the centres of the
sympathetic nervous system through the
anterior roots of the ganglia of the
The centres are situated at the level of the
thoracic and upper lumbar segments.
The grey communicating branch, the
postganglionic fibres, provide the
vasomotor and trophic processes in the
They connect the sympathetic trunk with
the spinal nerves for its entire length. The
cervical part of the sympathetic trunk is
also connected with the cranial nerves.
All the plexuses of the somatic nervous
system contain therefore fibres of the
sympathetic system in their bundles and
The sympathetic trunk
Sympathetic trunk is a r (or abdominal) and
pair formation, situated sacral (or pelvic).
at flanks of the spinal
cord, consists of 20-25
Each of the two
sympathetic trunk is
subdivided into four
cervical, thoracic, lumba
The cervical part stretches from the base of the skull to
the neck of the first rib, lies behind the carotid arteries on
the deep muscles of the neck. It has three cervical
sympathetic ganglia: superior, middle and inferior.
Superior cervical ganglion is the largest ganglion of the
sympathetic trunk, lies on the level of the 2nd and part of
the 3rd cervical vertebrae behind the internal carotid
artery and medial to the vagus nerve.
Middle cervical ganglion is small and usually located at
the intersection of the inferior thyroid artery with the
Inferior cervical ganglion is situated behind the initial part
of the vertebral artery, it is often fused with the 1st and
sometimes with the 2nd thoracic ganglion to form a
common inferior cervical ganglion.
The cervical ganglia
send nerves to the
head, neck and chest;
can be divided into an
passing to the head, a
stretching to the
heart, and a group
running to the organs
of the neck almost
immediately from the
site of origin.
Ascending group: the nerves of
the head arise from the superior
and inferior cervical ganglia and
separate into a group of nerves
that penetrate the cranial cavity
and a group of nerves that reach
the head from outer surface.
1st group is represented by the
internal carotid nerve, from the
superior cervical ganglion and
the vertebral branch of the
inferior cervical ganglion.
Both nerves form plexuses
around them, internal carotid
plexus and the vertebral plexus.
Together with the arteries passing through the
the nerves enter the cranial cavernous sinus.
cavity where they
anastomose with one
another and send branches
to the cerebral vessels, the
hypophysis, the trunk of the
3rd, 4th, 5th and 6th pairs of
cranial nerves and to the
The internal carotid plexus
is continuous with the
cavernous plexus which
surrounds the internal
carotid artery in the part
2nd group, external, consists of salivary), and to the muscle
two branches of the superior which dilates the pupil (m.
cervical ganglion, the external dilatator pupillae).
carotid nerves, which form
plexuses around the external
carotid artery and then pass in
attendance to its ramifications on
the head. The plexus sends a
small ramus to the optic
ganglion, the facial plexus gives
off a branch accompanying the
facial artery and passing to the
The superior cervical plexus
sends fibres to the vessels
(vasoconstrictors) and the glands
of the head
(sweat, lacrimal, mucous and
Descending group: is
formed by the cardiac
branches of the
superior, middle and
inferior cervical ganglia;
and together with the
cardiac branches of the
ganglia and branches
of the vagus nerve
contribute to the
formation of the cardiac
The thoracic part lies in ganglia and participates in
front of the neck of the ribs the formation of the cardiac
and is covered by pleura. It plexus.
consists of 10 to 12
ganglia. The thoracic part is
characterized by the
presence of white
which connect the anterior
roots of the spinal nerves
with the sympathetic trunk
ganglia. The five branches
1.Cardiac branch arises
from the superior thoracic
2.Grey communicating branches are non-
medullated fibres supplied to the intercostal nerves.
3.Pulmonary branches pass to the lungs to form the
4.Aortic branches form a thoracic aortic
plexus, partly on the oesophagus, oesophageal
plexus, and on the thoracic duct.
5.Greater and lesser splanchnic nerves:
The greater splanchnic nerve originates as several roots
from the 5th to 9th thoracic ganglia, which pass medially to
the level of the 9th thoracic vertebra where they fuse into
one common trunk which is transmitted through the
space between the muscular bundles of the
diaphragmatic crura into the abdominal cavity in which
becomes a component of the coeliac plexus.
The lesser splanchnic nerve arises from the 10th and 11th
thoracic ganglia, penetrates the diaphragm together with
the greater splanchnic nerve or is separated from it by a
few muscular bundles, and also becomes a component
of the coeliac plexus.
The lumbar (or abdominal) part consists of four
ganglia. Both sympathetic trunks come closer to each
other in the lumbar part, as a result of which the ganglia
lie on the anterolateral surface of the lumbar vertebrae on
the medial border of the psoas major muscle.
Along its entire distance the lumbar part sends off a great
number of branches which, together with the greater and
lesser splanchnic nerves and the abdominal segments of
the vagus nerve, form the largest unpaired coeliac
The coeliac plexus lies on the anterior semicircunference
of the abdominal aorta behind the pancreas and
surrounds the initial parts of the coeliac trunk and the
superior mesenteric artery.
Coeliac trunk occupies an
area between the renal
arteries, the suprarenal
glands, and the aortic
opening of the diaphragm
and includes the paired
ganglion of the coeliac
artery – coeliac
ganglion, and sometimes
the unpaired ganglion of
the superior mesenteric
mesenteric ganglion lying
under the root of this
The 2nd main source of ganglion whose
innervation of the abdominal postganglionic fibres pass to
organs is the aortic the pelvis as components of
plexus, formed by two trunks the hypogastric nerves.
arising from the coeliac
plexus and branches running
from the lumbar ganglia of the
Aortic plexus gives rise to the
inferior mesenteric plexus for
transverse, descending, and
sigmoid colon, and upper part
of the rectum. At the origin of
the inferior mesenteric plexus
lies the inferior mesenteric
Aortic plexus is relation to the penis and
continuous with the motor in relation to the
unpaired hypogastric uterus and the sphincter
plexus which bifurcates urethrae muscle.
at the promontory of the
sacrum and is in turn
continuous with the
Fibres derived from the
The sacral (or pelvic)
part, part usually has four
ganglia. Lying on the
anterior surface of the
sacrum along the medial
margin of the anterior
sacral foramen, both trunks
converge to terminate as
one common unpaired
ganglion impar on the
anterior surface of the
coccyx. The ganglia of the
pelvic part are connected
both by small longitudinal
and transverse trunks.
The parasympathetic system
The central part of the parasympathetic system
consists of the cranial nerves ( III, VII, IX and X);
III, VII and IX carry parasympathetic fibers to
structures within the head and neck only, whereas X
(the vagus nerve) also innervates thoracic and most
abdominal viscera; and spinal (or sacral) nerves S2
to S4, sacral parasympathetic fibers innervates
inferior abdominal viscera, pelvic viscera and the
arteries associated with erectile tissues of the
The centres give rise to the efferent fibres of the
posterior horns which cause dilation of the vessels
and inhibition of contraction of the smooth muscles
of the hair on the trunk and limbs.
The cranial part consists ciliaris)
of centres lodged in the
mesencephalic part and in
the bulbar part (pons and
1.Mesencephalic part is
represented by the
accessory nucleus of the
oculomotor nerve and by
the median unpaired
nucleus which are
responsible for the
innervation of the smooth
muscles of the eye (m.
sphincter pupillae and m.
2.Bulbar part is
represented by the
superior salivary nucleus
of the facial nerve, the
inferior salivary nucleus
of the glossopharyngeal
nerve, and the dorsal
nucleus of the vagus
The nucleus of the
sacral part lie in the
spinal cord, in the
nucleus of the lateral
horn at the level of
the 2nd to 4th sacral
The peripheral part of
system consist of:
passing in the
III, VII, IX and X pairs
of cranial nerves.
2.Terminal ganglia lying
close to the organs, the
3. Postganglionic fibres
which either stretch
independently, e.g. the
short ciliary nerves
arising from the ciliary
ganglion, or pass in some
other nerves, e.g.
originating from the optic
ganglion and running in
The peripheral part of the sacral parasympathetic
system consists of fibres which run in the anterior
roots of the 2nd, 3rd and 4th sacral nerves, in their
anterior branches forming the sacral plexus (somatic
plexus) and finally enter the true pelvis.
In the pelvis they leave the sacral plexus and as the
pelvic splanchnic nerves pass to the pelvis plexus
together with which they innervate the pelvic organs
(the rectum with the sigmoid colon, the urinary
bladder, and the external and internal genitalia).
Stimulation of the pelvic splanchnic nerves causes
contraction of the rectum and bladder with relaxation
of their sphincter muscles.
The fibres of the sympathetic hypogastric plexus, in
contrast, delay the evacuation of these organs; they
stimulate uterine contractions, while the pelvic
splanchnic nerves inhibit it.
The pelvic splanchnic nerves also contain vasodilator
fibres for the cavernous bodies of the penis and clitoris
which are responsible for the erection.
The parasympathetic fibres arising from the sacral
segment of the spinal cord extend to the pelvic plexuses
not only in the erigentes and pelvic splanchnic nerves but
also in the pudental nerve (the preganglionic fibers).
The pudental nerve is a complex nerve containing in
addition to somatic fibres; vegetative (sympathetic and
parasympathetic) fibres that form part of the inferior
The intramural nervous system also belongs to the PNS.
(intramural system are the walls of some hollow organs
that contain nerve plexuses of small ganglia with
ganglionic cells and non-medullated fibres).
Autonomic nervous system disorder
Dysautonomia (autonomic dysfunction) is a broad
term that describes any disease or malfunction of the
autonomic nervous system.
This includes: postural orthostatic tachycardia
syndrome (POTS), inappropriate sinus tachycardia
(IST), vasovagal syncope, pure autonomic
failure, neurocardiogenic syncope (NCS), neurally
mediated hypotension (NMH), orthostatic
hypertension, autonomic instability.
And a number of lesser-known disorders such as
cerebral salt-wasting syndrome. Dysautonomia is
associated with multiple system atrophy (Shy-Drager
syndrome), Ehlers-Danlos syndrome (EDS), and
Marfan syndrome for reasons that are not fully
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