Autonomic Nervous System (ANS)

The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies smooth muscle and glands, and thus influences the function of internal organs. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions, such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal.

1. Represented by-PawanKumar Sahu

2. Introduction
Autonomic is a combination of two words:
Autos-Self
Nomos-Regulating
This system is widely distributed throughout the body.
It controls tissue; Example-(Smooth muscle, Heart
and Glands) which are not under voluntary
control.
It controls visceral function such as circulation,
digestion and excretion etc.

3. Introduction
The autonomic nervous system consist of two
divisions:
1. Sympathetic Nervous System
2. Parasympathetic Nervous System

4. Introduction
The ‘Parasympathetic nervous system’ is mostly
concerned with the vegetative function. (Rest and Digest)
E.g.-Motility and secretions of gastro-intestinal tract. This
system is essential for the normal existence of the
organism.
The ‘Sympathetic nervous system’ is concerned with
preparing the organism for emergency. (Fear, Flight and
Fight)
Unlike the parasympathetic nervous system, the
sympathetic nervous system is not essential for normal
existence.

5. Introduction
Anatomically both the sympathetic and
parasympathetic nervous system consist of:
Preganglionic nerve Postganglionic nerve
Ganglion
1. Preganglionic nerve
2. Ganglion
3. Postganglionic nerve
4. Effectororgan
Effector
organ

6. 1. Sympathetic Nervous System
The autonomic nervous system functions to regulate the
body's unconscious actions.
The sympathetic nervous system's primary process is to
stimulate the body'sfight or flight response.
A pair of sympathetic chain are seen on either side of the
vertebral column.
Each sympathetic chain has:
a)Cervical part-has 3 ganglia
b)Thoracic part-has 12 ganglia
c)Lumbar part-has 4 ganglia
d)Sacral part-has 4 or 5 ganglia

7. a) Sympathetic preganglionic fibers
In sympathetic system the preganglionic fibers are short
and post ganglionic fibers are long.
The preganglionic fibers of the sympathetic nervous
system arise from the lateral horn cell of the spinal
cord. (situated at 1
st
thoracic and 3
rd
lumbar segment)
They pass through anterior nerve route of spinal nerve.
Then they run for a short distance in the spinal nerve.
From the spinal nerve, they are communicated to the
ganglia of sympathetic chain through ‘white rami
communicantes’.

8. b) Sympathetic postganglionic fibers
They are formed by ‘Gray rami communicantes’
which arise from ganglia of sympathetic chain.
They enters into spinal nerve of the same level and
reach the organ which they supply.
Some of fibers may ascend to higher ganglia or
descend to lower ganglia of the sympathetic chain.
They came out from a ganglion of appropriate level
through grey rami communicantesand enters into
spinal nerve.

10. Chemical Neurotransmitters of SNS
The Neurotransmitter in the preganglionic
sympathetic nerve in Acetyl choline(Ach), which
is liberated at the ganglion.
But in postganglionic sympathetic nerve
‘Noradrenaline’ is the transmitter. It is liberated at
the postganglionic sympathetic nerve ending.

11. Receptors
Adrenergic receptors: The receptor present at the
postganglionic sympathetic nerve ending are
called ‘Adrenergic receptors’.
They are;
receptors: The action on which is excitatory.
(except intestine)
receptors: The action on which is inhibitory.
(except heart)

12. Function
Organ Effect
Eye Dilates
Heart Increases rate and force of contraction
Lungs Dilatesbronchiolesvia circulating
adrenaline
Blood vessels Dilate in skeletal muscle
Digest system Constricts in gastrointestinal organs
Sweat glands Activates sweat secretion
Digestivetract Inhibitsperistalsis
Kidney Increasesreninsecretion
Penis Inhibitstumescence
DuctusdeferensPromotes emission prior to ejaculation
Organ Effect
Eye Dilates
Heart Increases rate and force of contraction
Lungs Dilatesbronchiolesvia circulating
adrenaline
Blood vessels Dilate in skeletal muscle
Digest system Constricts in gastrointestinal organs
Sweat glands Activates sweat secretion
Digestivetract Inhibitsperistalsis
Kidney Increasesreninsecretion
Penis Inhibitstumescence
DuctusdeferensPromotes emission prior to ejaculation

13. Notes
Noradrenalineacts only on receptors.
Isoprenalineacts only on receptors.
Adrenaline acts on bothand receptors.
Ach Noradrenaline
Preganglionicsympathetic nerve Postganglionic sympathetic nerve
Ganglion
Effector
organ

14. 2. Parasympathetic nervous system
Theparasympathetic nervous system(PSNS) is one
of the two divisions, the other being thesympathetic,
that together are called theautonomic nervous
system, which is a division of another system called
theperipheral nervous system(PNS).
The parasympathetic system is responsible for
stimulation of "rest-and-digest" or "feed and
breed"activities that occur when the body is at rest,
especially after eating, includingsexual
arousal,salivation,lacrimation(tears),urination,
digestionanddefecation.

15. a) Parasympathetic preganglionicfibers
The preganglionicfibersof parasympathetic nerve arise from cells,
present in the mid brain, medulla and sacral portion of spinal
cord.
They may as follows;
From the mid brain, fibersemerge through oculomotornerve (move
eye).
From the medulla, they emerge throughfacial, glossopharyngeal
and vagusnerve.
At the sacral portion of spinal cord, they arise from the anterior
column of 2
nd
, 3
rd
and 4
th
lumbar segments.They taken pass
through anterior roots of the corresponding spinal nerve.
All these nerves (which have three different origins) end in a ganglion
each.
These parasympathetic ganglia are very near to the structure which
these nerve supply.

16. b) Parasympathetic postganglionic fibers
They arise from the ganglia and then reach the
structures which these nerve supply.

17. Chemical Neurotransmitters of PSNS
The transmitter in preganglionicparasympathetic nerve
is Acetylcholine (Ach), which is liberated at the
ganglia.
The transmitter in the postganglionic parasympathetic
nerve ending is also Acetylcholine (Ach).
Preganglionic Ach Postganglionic Ach
Parasympathetic nerve Parasympathetic nerve
Ganglia
Effector
organ

18. Receptors
Cholinergic receptors: The receptor for acetylcholine
are called as cholinergic receptors.
They are present at:
1.Nicotinic receptors: They are present at both
sympathetic and parasympathetic ganglia.
They are also present atneuromuscular junction.
They are two types:
i.N
N receptor: Present on autonomic ganglia and
adrenal medulla.
ii.N
M receptor: Present in neuromuscular junction.

19. Receptors
2.Muscarinicreceptors: They are present at
postganglionic parasympathetic nerve ending.
They are three types:
i.M
1 :Present at gastric gland, CNS, autonomic
ganglia.
ii.M
2 : Heart
iii.M
3 : Present at smooth muscles and exocrine
gland.

20. Function
Organ Effect
Eye Contracts
Heart Decreases rate and force of contraction
GIT Contractsthe propulsive activity of GIT
Blood vessels Constrictblood vessel
Excretorysystem Contracts the bladder wall
Salivary glands Watery secretion
Respiratory
system
Contracts the bronchomuscles
Tracheaand
bronchioles
Constrictionand increase secretion
Lacrimalglands Stimulation of tears
Ductusdeferens Increaseerection