Autonomic Nervous
System (ANS) II
By
Dr. Khaled Ibrahim Khalil
At the end of this session, the student should be able to:
a. Describe the origin and the actions of ANS to:
 Thorax.
 Abdomen and
 Pelvis.
b. Relate these actions to manifestations of autonomic disorders.
 GUYTON & HALL Textbook of Medical Physiology, 12th edition, page: 734-739
Sympathetic nervous system
Catabolic
Parasympathetic nervous system
Anabolic
Preserve energy in the body (i.e. save energy in the
Increases energy expenditure of the body.
heart and offer it in the intestine).
Prepares the body for activity, increasing the capacity Predominates
during
sleep
where
there
are
to perform sever muscular effort (fight and flight) in
continuous digestion, slow heart rate and constricted
response to stress (emergency situations).
pupil.
Delay onset of fatigue of contracting muscles
Allow for repair and recovery of contracting muscles.
Sympathetic mass stimulation is useful
Parasympathetic mass stimulation is fatal.
ORIGIN OF AUTONOMIC NERVOUS SYSTEM
Sympathetic nervous system
Parasympathetic nervous system
(Thoracolumbar outflow)
(craniosacral outflow)
1) CRANIAL PART
LHCs of all
thoracic and
upper 3 lumbar
segments of the
spinal cord.
2) SACRAL PART
visceral motor
2nd, 3rd and 4th sacral
nuclei of cranial
segments of the spinal
nerves
cord. The preganglionic
III, VII, IX and X
fibers unite to form the
pelvic nerve.
Actions on Thorax
Sympathetic
Parasympathetic
Origin
LHCs of upper 4 or 5 thoracic segments of spinal cord
Dorsal Motor nucleus of the vagus
Relay
Cervical ganglia (superior, middle and inferior) and Terminal ganglia in the wall of the heart and lung
upper 4 thoracic ganglia
a) Sympathetic stimulation increases the effectiveness Parasympathetic
stimulation
decreases
the
of the heart as a pump i.e. increasing the rate, force of effectiveness of the heart as a pump i.e. decreasing the
heart contraction, conduction velocity, excitability, rate, force of heart contraction, conduction velocity,
Action on the
heart
cardiac metabolism and O2 consumption.
excitability, cardiac metabolism and O2 consumption.
b) Coronary vessels: Direct effect is vasoconstriction.  Coronary vessels : Direct effect is vasodilatation.
Indirectly the coronary vessels dilate as a result of Vagal stimulation inhibits cardiac work with less
accumulation of metabolites of the stimulated heart.
production of metabolites. Thus the coronary vessels
indirectly constrict (vasoconstriction).
a) inhibition of the smooth muscles of the bronchial tree a) Motor to the smooth muscles of the bronchial tree
Action of the
lungs
resulting in bronchodilatation
b) inhibition of the mucus secretion of air passages.
c) vasoconstriction of the pulmonary blood vessels.
 N.B.: Parasympathetic does not supply the ventricles.
resulting in bronchoconstriction.
b) Stimulate the mucus secretion of the air passages.
c) Vasodilatation of the pulmonary blood vessels.
Actions on Abdomen
(1) GIT
• (Stomach, small intestine and proximal part of large intestine)
• Relaxation of their walls and contraction of their sphincters leading to inhibition
of digestion and delayed evacuation of their contents.
(2) Liver:
• Stimulation of glycogenolysis leading to increased blood glucose.
• Stimulation of fibrinogen synthesis.
(3) Gall bladder:
• contraction of wall and relaxation of sphincter of Oddi, helping its evacuation.
(4) Spleen:
• Contraction of smooth muscles in splenic capsule and trabeculae leading to
pouring of about 250 ml of stored blood into the general circulation.
(5) Pancreas:
• Sympathetic stimulation usually inhibits pancreatic secretion (both endocrine and
exocrine components).
(6) Blood vessels
• Mixed supply (vasoconstriction and vasodilatation).
(7) Kidneys:
• Stimulation of juxta glomerular cells leading to increased renin secretion.
• Decrease renal blood flow.
• Decrease urine output.
Sympathetic
origin
LHCs of T6-12
segments of
spinal cord
(splanchnic
nerves).
Relay
Collateral
ganglia (celiac,
superior
mesenteric,
aortico-renal)
and terminal
ganglia
(1) GIT
• (Stomach, small intestine and proximal part of large intestine)
• contraction of their walls and relaxation of their sphincters enhancing both
digestion and evacuation of GIT contents i.e. help deglutition, gastric motility, and
peristaltic movement of GIT.
Parasympathetic
origin
(2) Liver:
• increased hepatic bile flow.
(3) Gall bladder:
• Relaxation of its wall and contraction of sphincter of oddi leading to retention of
bile and delayed emptying of gall bladder.
Dorsal motor
nucleus of the
vagus
Relay
(4) Pancreas:
• Parasympathetic stimulation usually stimulates pancreatic secretion (both
endocrine and exocrine components).
(5) Blood vessels
• Vasodilatation.
(6) Glands:
• Stimulation of gastric juice secretion (rich in HCl).
• Stimulation of alkaline mucus secretion from Bruner's glands in the duodenum.
Terminal ganglia
in the wall of
abdominal
organs
Action of sympathetic on Suprarenal medulla
Origin: LHCs of T10,11 segments of spinal cord.
* SRM has special character being supplied by sympathetic preganglionic nerve fibers (with no
postganglionic nerve fibers) which relay there on special neurosecretory cells (chromaffin cells).
* Stimulation of sympathetic nerves to SRM releases large quantities of adrenaline (80%) and
noradrenaline (20%) into the circulating blood, being carried to all body tissues. These hormones has
prolonged action due to their slow clearance from the circulation.
- Adrenaline acts more on metabolic actions of the body while noradrenaline acts more on blood vessels.
- In stress conditions, SRM acts together with sympathetic nervous system (sympatho-adrenal system).
Actions on Pelvis
Sympathetic
Parasympathetic
Origin
LHCs of L1, L2, L3 segments of spinal cord.
Sacral segments 2, 3, 4 (preganglionic forms pelvic nerve)
Relay
Collateral ganglia (inferior mesenteric or hypogastric
ganglia) and terminal ganglia
Terminal ganglia in the wall of the pelvic organs
Action on
Urinary
bladder
Contraction of its wall and relaxation of internal
relaxation of its wall and contraction of internal
urethral sphincter leading to micturition.
urethral sphincter leading to urine retention.
Action of the
rectum
relaxation of its wall and contraction of internal anal Contraction of its wall and relaxation of internal anal
sphincter leading to retention.
sphincter leading to defecation.
a) Contraction of smooth muscles in the walls of a) Vasodilatation of the blood vessels of the pelvic
seminal vesicle, epididymis, vas deferens and
Action of male
viscera including that of sex organs leading to
ejaculatory duct leading to ejaculation of semen.
sex organs
erection of the penis, clitoris, etc. and congestion of
b) Vasoconstriction of blood vessels of pelvic viscera
including those of external sex organs leading to
the labia. So, the pelvic nerve is named as the
shrinkage of penis.
nervus erigenus.
a) Vasoconstriction of blood vessels of external sex
Action of
b) Secretory to the seminal vesicles, prostate and other
organs leading to shrinkage of clitoris.
female sex
b) Variable effects on smooth muscles of uterus,
accessory glands.
organs
mainly inhibitory but may be excitatory in late
pregnancy.
Sympathetic
Parasympathetic
(I) Antagonistic functions:
1- Pupil:
2- Air passages.
3- Heart
Mydriasis.
bronchodilatation.
 rate
Miosis.
bronchoconstriction.
 rate
 contraction
 coronary blood flow
 contraction
 coronary blood flow
relaxation
contraction
vasoconstriction
retention of faeces
contraction
relaxation
vasodilatation
defecation
4- GIT:
- Wall
- Sphincter
- Blood vessels
5- Rectum
retention of urine
7- blood vessels
Vasoconstriction
(II) Synergistic function: (During salivary secretion)
Trophic salivary secretion
(little, viscid, rich in enzymes)
6- Urinary bladder
Micturition
vasodilatation
True salivary secretion
(large in volume, watery, rich in electrolytes)
N.B.: Augmented secretion
Stimulation of sympathetic to salivary glands after parasympathetic stimulation leads to augmented secretion due to active squeeze of acini as a result of
sympathetic stimulation of myoepithelial cells surrounding acini (which are filled with secretions by parasympathetic stimulation).
(III) Cooperative functions: (During sexual intercourse)
* Contraction of vas deference, seminal vesicle, ejaculatory duct;
* Secretory to seminal vesicle and prostate.
producing ejaculation of semen.