The nervous system controls and coordinates the activities of the body. It has both voluntary and involuntary functions. The autonomic nervous system regulates involuntary functions like heart rate and digestion. It has two divisions - the sympathetic and parasympathetic systems which generally have opposing effects on organs. The sympathetic system prepares the body for fight or flight while the parasympathetic maintains normal functions. Dysfunctions of the autonomic nervous system can cause issues like high blood pressure, digestive problems, and more.

1. Introduction to Nervous System
 Nervous system is the chief and master controlling and communicating system of the body.
 It is most complex and most evolved system of body at the cost of regeneration.
 It controls both type of activities voluntary as well as involuntary by providing an organized network of point
to point and precise connections.
The nervous system has three overlapping functions -
 It uses its millions of sensory receptors to monitor changes occurring both in side as well as out side to body.
These changes are called as stimulus.
 It processes and interprets the stimulus and makes decision about what should be done over come the
situation.This process is called as integration.
 It dictates a response by activating the effectors organ, muscle or gland.
Stimulus
Receptor
organ
Nervous
system
Effector Response

2. Embryological Development of Nervous System:
Development of the nervous system in weeks 4 and 5 of the embryonic period. (a).Cross section of the neural tube,
the future spinal cord and brain. (b). Neuroblasts (future neurons) arise through division of neuroepithelial cells and
migrate externally. (c). Neuroblasts from the alar plate (future interneurons) and basal plate (future motor neurons).

3. Development of CNS

4. Nervous
system
PNS
Cranial neves
and Spinal
nerves.
Sensory
[Afferent]
Division .
Somatic sensory
General
Touch,Pain,Pressure,Vibration,Temperature and
proprioception in skin and body wall.
Special - Vision,Smell,Hearing,Equilibrium.
Visceral sensory
General
Stretch,Pain,Temperature,Chemicalchanges and
irritation in viscera,nausea and hunger.
Special - Taste .
Motor
[Efferent]
Division.
Somatic motor
General- motor innervation of all skeletal muscles
[except pharyngeal arch muscles ]
Visceral motor
General
Motor innervation of smooth muscle ,cardiac
muscle,and glands ,equal to automnomic nervous
system[ANS].
Special- Motor innervation of pharyngeal arch muscles.
.
CNS
Brain and
Spinal cord .

5. Difference between autonomic and somatic neuron

6. Introduction to the Autonomic Nervous
system :
The ANS is the system of motor neurons that innervate
the smooth muscle, cardiac muscle, and glands of the
body. By controlling these effectors, the ANS regulates
such visceral funtions as heart rate, blood pressure,
digestion, and urination. These functions are essential for
maintaining the stability of the body's internal
environment. The ANS is the general visceral motor
division of the peripheral nervous system, according to
the classification of nervous outputs the ANS is distinct
from the general somatic motor division (Which
innervates the somatic skeletal muscles) and the special
visceral motor division (which innervates the pharyngeal
arch muscles).

7. Divisions of the Autonomic
Nervous System :
The ANS has two divisions, the
sympathetic and parasympathetic. Both
divisions generally innervate the same
visceral organs, but cause opposite
effects: Where one division stimulates
some smooth muscle to contract or a
gland to secrete, the other division
inhibits that action.

8. The Parasympathetic Division
The cranial part of the parasympathetic division innervates organs in the head, neck, thorax, and most of the
abdomen.The sacral part supplies the rest of the abdominal organs and the pelvic organs.
Cranial Outflow
The cranial parasympathetic outflow is
contained in several cranial nerves. More
specifically, the preganglionic fibers run in
the oculomotor, facial, glossopharyngeal,
and vagus nerves.

9. Oculomotor Nerve (III)
The parasympathetic fibers of the oculomotor nerve
innervate smooth muscles in the eye that cause the
pupil to constrict and the lens of the eye to bulge
actions that allow focusing on close objects in the
field of vision.
Facial Nerve (VII)
The parasympathetic fibers of the facial nerve stimulate the
secretion of many glands in the head, including two salivary
glands inferior to the mouth, called the submandibular and
sublingual glands; the lacrimal (tear) gland above the eye;
and mucus-secreting glands in the nasal cavity.

10. Glossopharyngeal Nerve (IX)
The parasympathetic fibers of the glossopharyngeal
nerve stimulate secretion of a large salivary gland
called the parotid gland, which lies anterior to the ear.
Vagus Nerve (X)
Parasympathetic fibers from one additional cranial
nerve, the vagus nerve, innervate the visceral organs of
the thorax and most of the abdomen.

11. The sacral part of the parasympathetic
outflow comes from the S2–S4 segments of
the sacral spinal cord (Figure 14.3). It
supplies the organs in the pelvis, including
the distal half of the large intestine, the
bladder, the reproductive organs (the
uterus, for example), and the erectile
tissues of the external genitalia.
Parasympathetic effects on these organs
include stimulation of defecation, voiding of
urine, and erection
Sacral Outflow

12. The Sympathetic Division
The sympathetic division is more complex than the parasympathetic division, in part because it innervates more
organs. It supplies not only all the visceral organs in the internal body cavities but also -all visceral structures in
the superficial regions of the body: the sweat glands, the hair-raising arrector pili muscles of the skin, and the
smooth musculature in the walls of arteries and veins.
SYMPATHETIC GANGLIA
Chain or
paravertebral
ganglia
Many chain ganglia line up vertically
along both sides of the vertebral
column, from the neck to the pelvis.
Successive chain ganglia are
interconnected by short nerves into
long sympathetic trunks. Each
sympathetic trunk resembles a strand
of beads. There is approximately one
chain ganglion for each spinal nerve.
Pre vertebral or
collateral
ganglia
They are not paired and are not
segmentally arranged. they are confined
to the abdomen and pelvis and they all
lie anterior to the vertebral column
mostly on the abdominal aorta. The
main prevertebral ganglia are the celiac,
superior mesenteric, inferior mesenteric,
and inferior hypogastric ganglia.

13. Differences between the sympathetic and parasympathetic pathway.

14. Characteristic Sympathetic Parasympathetic
Origin Thoracolumbar outflow: lateral horn of gray matter of spinal cord
segments T,-L2
Craniosacral outflow: brain stem nuclei of cranial nerves
III,VII,IX,andX;spinalcordsegmentsS2-S4
Locationofganglia Ganglia within afewcmofCNS:alongside vertebralcolumn
(paravertebralganglia) and anteriorto vertebralcolumn
(prevertebral ganglia)
Ganglia in or close to visceral organ served
Relative length of pre- and postganglionic fibers Rami
communicantes
Shortpreganglionic; longpostganglionic Long preganglionic; short postganglionic
Degreeofbranchingofpreganglionicfibers Extensive Minimal
Functionalgoal Prepares body tocope withemergenciesand intense muscular
activity
Maintenance functions;conservesand storesenergy
Neurotransmitters Allpreganglionicfibersrelease ACh mostpostganglionicfibers
release norepinephrine (adrenergicfibers)somepostganglionic
fibers(e.g.,thoseservingsweat glands and bloodvesselsofskeletal
muscles)release ACh,neurotransmitteractivity augmented by
release ofadrenal medullaryhormones(norepinephrine and
epinephrine)
All fibersrelease ACh (cholinergicfibers)

15. Target organ Sympatheticeffects Parasympathetic effects
Eye (iris) Stimulatesdilatormuscles,dilateseye pupils Stimulates constrictor muscles; constricts eye pupils
Eye (ciliarymuscle) No effect Stimulates muscles, which results in bulging of the lens for accommodation and
close vision
Glands(nasal,lacrimal,salivary,gastric,pancreas) Inhibitssecretoryactivity;causesvasoconstriction of blood vessels supplying the glands Stimulatessecretoryactivity
Sweatglands Stimulatescopioussweating(cholinergicfibers) No effect
Adrenal medulla Stimulatesmedullacellstosecreteepinephrineandnoreppinephrine No effect
Arrector pili muscles attachedto hair follicles Stimulatestocontract(erectshairsandproducesgooseburmps0 No effect
Heart muscle Increasesrateandforceofheartbeat Decreasesrate slows andsteadiesheart
Heart: coronary blood vessels Causesvasodilation Constrictscoronaryvessels
Bladder/ urethra Causesrelaxationofsmoothmuscleofbladderwallconstrictsurethralspphincterinhibitsvoiding Causes contraction of smooth muscle of bladder wall; relaxes urethral sphincter;
promotesvoiding
Lungs Dilatesbronchiolesandmildlyconstrictsblood vessels Constrictsbronchioles
Digestive tract organs Decreases activity of glands and muscles of digestive system and constricts sphincters (e.g., anal
sphincter)
Increases motility (peristalsis) and amount of secretion by digestive organs; relaxes
sphinctersto allowmovementof foodstuffsalong tract
Gallbladder Inhibits(gallbladderisrelaxed) Excites(gallbladdercontractstoexpelbile)
Kidney Causesvasoconstictiondecreasesurineoutput Noeffect
Penis Causesejaculation Causeserection(vasodilation)
Vagina/clitoris Causesreverseperistalsis(contraction)ofvagina Causeserection(vasodilation)ofclitoris
Blood Vessels Constricts most vessels and increases blood pressure; constricts vessels of abdominal viscera
and skin to divert blood to muscles, brain, and heart when necessary; dilates vessels of the
skeletal muscles (cholinergic fibers)duringexercise
Littleorno effect
Blood coagulation Increasescoagulation Noeffect
Cellular metabolism Increasesmetabolicrate Noeffect
Adipose tissue Stimulateslipolysis(fatbreakdown) Noeffect

16. Pathways to the Body Periphery
The vagus nerve, the autonomic nerve plexuses, and the autonomic ganglia throughout the body. All
autonomic plexuses are shared by both parasympathetic and sympathetic fibers, but the ganglia in these plexuses are
almost exclusively sympathetic. Also note the sympathetic chain ganglia.

17. Sympathetic pathways
This diagram indicates the relationship of the
sympathetic neurons to the spinal cord, sympathetic
trunks, and associated structures. Preganglionic
neurons in the spinal cord, labeled a—c, send fibers to
the chain ganglia. There, these fibers may synapse with
a postganglionic neuron in a chain ganglion (neuron a)
or may pass through to synapse in a prevertebral
ganglion (neuron c). Also, a preganglionic fiber may
ascend or descend in the sympathetic trunk (neuron b)
before synapsing in a chain or prevertebral ganglion.

18. Pathway of sympathetic and parasympathetic fibres

19. Central Control of the Autonomic Nervous System
Although the ANS is not considered to be under direct voluntary control, its performance is nevertheless
regulated by the central nervous system.
Control by the Brain Stem and Spinal Cord
The reticular formation of the brain stem appears to exert the most direct influence over autonomic functions.
Centers in the medulla oblongata regulate heart rate (cardiac center), the diameter of blood vessels (vasomotor
center), many types of digestive activities (vomiting center), and respiration rate (respiratory centers).Control of
autonomic functions at the level of the spinal cord involves the spinal visceral reflexes.
Control by the Hypothalamus
The integration center of the autonomic nervous system is the hypothalamus. These hypothalamic centers exert
their effects indirectly via relays through the reticular formation. It is through the ANS that the hypothalamus
controls heart activity, blood pressure, body temperature, and digestive functions.
Control by the Cerebral Cortex
People can learn to control some autonomic functions indirectly by developing extraordinary control over their
emotions. For example, feelings of extreme calm are associated with parasympathetic activation.

20. Referred Pain
People suffering from visceral pain often perceive this
pain as somatic in origin—as if it originated from the skin
or outer body. This is called referred pain. For example,
heart attacks can produce pain in the superior thoracic
wall and the medial aspect of the left arm. The cause of
referred pain is not fully understood. However, it is
known that both the affected organ and the region of
the body wall to which the pain is referred are
innervated by the same spinal segments. (For
example, both the heart and the skin area to which
heart pain projects are innervated by sensory neurons
from T1 to T5) The current view is that damage to the
visceral organ causes painful, reflexive vasoconstriction
in the corresponding somatic segments.

21. Pathology of the Autonomic Nervous System
Since the ANS is involved in nearly every important process that occurs within the body, it is not surprising that
abnormalities of autonomic functioning can have far-reaching effects. Such abnormalities can impair blood
delivery and elimination processes and can threaten life itself.
 Raynaud's disease is characterized by intermittent
attacks, during which the skin of the fingers and toes
becomes pale, then blue and painful. The severity of this
disease ranges from mere discomfort to such extreme
constriction of vessels that gangrene (tissue death)
results. Raynaud's disease is treated with drugs that
inhibit vasoconstriction. In severe cases, however,
cutting the preganglionic sympathetic fibers serving the
affected region is necessary. The involved vessels then
dilate, reestablishing adequate blood delivery.

22.  Hypertension, or high blood pressure, can result from overactive sympathetic vasoconstriction promoted
by continual stress. Hypertension is always serious because (1) it increases the work load on the heart,
possibly precipitating heart disease and (2) it increases the wear and tear on the artery walls. Stress-induced
hypertension is treated with drugs that prevent the muscle cells in the walls of blood vessels from binding
with norepinephrine and epinephrine.
 Achalasia of the cardia is a condition in which the
esophagus loses its ability to propel swallowed food
inferiorly. Additionally, the smooth muscle surrounding the
inferior end of the esophagus (cardiac sphincter) contracts
to block the passage of food into the stomach (achalasth
means "failure to relax"). Accumulating food stretches the
esophagus to enormous width, and meals cannot be kept
down. This condition usually appears in young adults and is
thought to result from an insufficient number of
parasympathetic postganglionic neurons in the esophagus
wall.

23.  Congenital megacolon or Hirschsprung's
disease is a birth defect in which the parasympathetic
innervation of the distal region of the large intestine fails to
develop normally. Feces accumulate proximal to the
immobile bowel segment, greatly distending this area
(megacolon = enlarged large intestine). The condition is
corrected surgically by removing the inactive part of the
infant's intestine.