Organization of ANS

2. Nervous System

3. BRIEF INTRODUCTION TO NERVOUS SYSTEM
 The nervous system is divided into anatomical divisions : CNS
which is composed of composed of the brain and spinal cord,
and PNS which includes neurons located outside the brain and
spinal cord i.e. any nerve that enter or leaves the CNS.
 The peripheral nervous system is further subdivided into the
efferent divisions , the neurons of which carry signals away
from the brain and spinal cord to the peripheral tissues, and the
afferent division, the neurons of which bring information from
periphery to the CNS.

4. WHAT IS AUTONOMIC SYSTEM?
 The autonomic nervous system (ANS) is largely autonomous
(independent) in that its activities are not under direct
conscious control.
 It is concerned with visceral functions-cardiac output, blood
flow to various organs, digestion, etc- that are necessary for
life.

5. Autonomic Nervous System And Endocrine
System
 The autonomic nervous system, along with the endocrine
system coordinates the regulation and integration of bodily
functions.
 The endocrine system sends signals to target tissues by
varying the levels of blood borne hormones.
 In contrast, the nervous system exerts its influence by the
rapid transmission of electrical impulses over nerve fibers
that terminate at effector cells, which specifically respond to
the release of neuromediator substances

6.  Preganglionic neurons in the CNS send axons
to synapse on ganglionic neurons in
autonomic ganglia outside the CNS
 Preganglionic neuron’s body lies in the CNS
 Postganglionic axons of ANS are usually
unmyelinated
CNS (brain
and Spinal
Cord)
PreganglionicGanglionPostganglionic

7. ORGANISATION OF AUTONOMIC
NERVOUS SYSTEM

10. 1. EFFERENT NEURONS
 The ANS carries nerve impulses from the CNS to the
effector organs by way of two types of efferent neurons.
 The first nerve cell is called a preganglionic neuron, and its
cell body is located within the CNS . Preganglionic neurons
emerge from the brainstem or spinal cord and make a
synaptic connection in ganglia(an aggregation of nerve cell
bodies located in the peripheral nervous system).

11.  These ganglia function as relay stations between a
preganglionic neuron and a second nerve cell, the
postganglionic neuron . The latter neuron has a cell body
originating in the ganglion .It is generally nonmyelinated and
terminates on effector organs, such as smooth muscles of the
viscera, cardiac muscle and the exocrine glands

12. 2. AFFERENT NEURONS
 The afferent neurons of the ANS are important in the reflex
regulation of this system.
 For example:- By sensing pressure in the carotid sinus and
aortic arch and in signaling the CNS to influence the
efferent branch of the system to respond.

13. 3. SYMPATHETIC NEURONS
 Anatomically, the sympathetic and parasympathetic neurons
originate in the CNS and emerge from two different spinal cord
regions.
 The preganglionic neurons of the sympathetic system come from
thoracic and lumbar regions (T1 and L2) of the spinal cord , and
they synapse into two cord like chains of ganglia that run close to
and parallel on each side of the spinal cord.
 Axons of the postganglionic neuron extend from these ganglia to
the tissues that they innervate and regulate.
 The sympathetic nervous system is also called thoracolumbar
division because of its origin.
 In most cases, the preganglionic endings of sympathetic nervous
system are highly branched enabling one preganglionic neuron to
interact with many postganglionic neurons.
 This arrangement enables them to activate numerous effector
organs.

15. 4. PARASYMPATHETIC NEURONS
 The parasympathetic preganglionic fibers arise from cranial
nerves 3 (oculomotor), 7(facial), 9 (glossopharyngeal) and
vagus as well as from the sacral regions (S2 and S4) of the
spinal cord and synapse in ganglia near or on the effector organ.
 They are also called as cranio-sacral division

16. 5. ENTERIC NEURONS
 The enteric nervous is the third division of the ANS.
 It is a collection of nerve fibers that innervate the gastro
intestinal (GI) tract, pancreas, gallbladder.
 It constitutes the “BRAIN OF THE GUT”
 This system functions independently of the CNS and controls
the motility, exocrine and endocrine secretions, and
microcirculation of the GI tract.

18. FUNCTION OF ANS
Autonomic because the autonomous autonomic nervous system
regulates them.
Regulating, adjusting, and coordinating vital visceral functions:
Blood pressure and blood flow
Body temperature
Diameter of bronchi
Digestion
Metabolism
Elimination