Autonomic nervous system

1. Sarita Sharma
Assistant professor of
pharmacology
Mumbai

3. • Handles the CNS’s input and output.
• Contains all the portions of the NS outside the brain and
spinal cord.
• Contains sensory nerves and motornerves
• Divided into autonomic nervous system and somatic
nervous system.

4. • Sensory Nerves
(to the brain)
Carry messages from
receptors in the skin,
muscles, and other
internal and external
sense organs to the
spinal cord and then
to the brain
• MotorNerves
(fromthe brain)
Carry orders from CNS
to muscles, glands to
contract and produce
chemical
messengers

5. • The ANS is part of the peripheral nervous
system and it controls many organs and muscles
within the body.
• In most situations, we are unaware of the
workings of the ANS because it functions in an
involuntary, reflexive manner.
• For example, we do not notice when blood
vessels change size or when our heart beats
faster.

6. • Somatic NS
Consists of nerves
connected to sensory
receptors and skeletal
muscles
Permits voluntary action
(writing your name)
• Autonomic NS
Permits the
Involuntary functions
of blood vessels,
Glands and
internal organs
e.g.:- the bladder
stomach
heart

8. SOMATIC
Afferent neuron terminate in dorsal
horn.
Efferent neuron cell body in ventral
horn.
Single efferent neuron
Innervates skeletal muscles.
Neurotransmitter – Ach
Activity – excitation.
Always voluntary.
ANS
Afferent neuron terminate in
intermediolateral horn.
Efferent neuron cell body in autonomic
ganglia.
2 efferent neurons.
Innervates smooth muscle, cardiac
muscle , secretory glands
Neurotransmitter – Ach & NE.
Activity – Excitation & inhibition.
Usually Involuntary.

9. Characteristic Somatic nervous
system
Autonomic N.
system
Effectors Voluntary muscle Cardiac muscle glands,
s. muscle
General functions Adjustment to external
environment
Adjustment within
internal environment
Numbers of neurons 1 2
Nerve fibres Myelinated Preganglionic –
Myelinated
Postganglionic – Non-
myelinated
Neurotransmitter acetylcholine Acetylcholine,
adrenaline,
noradrenaline

10. • Autonomic nervous system
• Chain of two motor neurons
• Preganglionic neuron
• Postganglionic neuron
• Conduction is slower due to thinly or unmyelinated axons
Pre-ganglionic
Ganglion
Post-ganglionic

11. The ANS is most important
in two situations:
1- In emergencies that
cause stress and
require us to "fight" or
take "flight" (run
away).
2- In no emergencies
that allow us to "rest"
and "digest".

12. Autonomic Nervous System
• Often work in
opposition
• Cooperate to fine-
tune homeostasis
• Regulated by the
brain;
hypothalamus, pons
and medulla
• Pathways both
consist of a two
neuron system
Preganglionic neuron autonomic ganglion postganglionic neuron target
from CNS outside CNS

13. Hypothalamus activates
sympathetic division of
nervous system
Heart rate, blood pressure,
and respiration increase
Blood flow to
skeletal muscles
increases
Stomach
contractions
are inhibited
Adrenal medulla
secretes
epinephrine and
norepinephrine

16. The Autonomic SystemThe Autonomic System

17. Sympathetic
• Sometimes called the
“thoracolumbar” division
• Short preganglionic neurons;
long postganglionic neurons;
ganglia are called the chain
ganglia
• Preganglionic neurons secrete
Ach onto nicotinic receptors
• Postganglionic neurons
secrete NE on to α or β
receptors
• Target tissues are smooth
muscle, cardiac muscle,
endocrine glands, brown fat

18. Parasympathetic
•Sometimes called the
“cranio-sacral division
•Long preganglionic
neurons;
•short postganglionic
neurons (often in the
target organ)
•Preganglionic neurons
secrete Ach on to
nicotinic receptors
•Postganglionic neurons
secrete Ach on to
muscarinic receptors
•Target tissues are
smooth muscle,
cardiac muscle,
exocrine glands, brown
fat

20. Similarities between Sympathetic & ParasympatheticSimilarities between Sympathetic & Parasympathetic
• Both involve regulation of the “internal” environment generally
outside of our conscious control: “autonomous”.
• Both involve 2 neurons that synapse in a peripheral ganglion
and Innervate glands, smooth muscle, cardiac muscle
CNS ganglion
preganglionic
neuron
postganglionic
neuron
glands
smooth
muscle
cardiac
muscle

21. Differences between Sympathetic & ParasympatheticDifferences between Sympathetic & Parasympathetic
Location of Preganglionic Cell Bodies
Thoracolumbar
T1 – L2/L3 levels
of the spinal cord
Craniosacral
Brain: CN III, VII, IX, X
Spinal cord: S2 – S4
Sympathetic Parasympathetic

22. Sympathetic
CNS ganglion
short preganglionic
neuron
long postganglionic
neuron
target
Parasympathetic
CNS ganglion
long preganglionic
neuron
target
short postganglionic
neuron
Differences between Sympathetic & ParasympatheticDifferences between Sympathetic & Parasympathetic
Relative Lengths of Neurons

23. Parasympathetic
Overview of the Autonomic Nervous SystemOverview of the Autonomic Nervous System
Differences between Sympathetic & ParasympatheticDifferences between Sympathetic & Parasympathetic
Neurotransmitters
ACh, +
NE (ACh at sweat glands),
+ / -, α & ß receptors
ACh, + / -
muscarinic receptors
• All preganglionics release acetylcholine (ACh) & are excitatory (+)
• Symp. postgangl. — norepinephrine (NE) & are excitatory (+) or inhibitory (-)
• Parasymp. postgangl. — ACh & are excitatory (+) or inhibitory (-)
Sympathetic
• Excitation or inhibition is a receptor-dependent & receptor-mediated response
ACh, +

25. Sympathetic nervous systemSympathetic nervous system Parasympathetic nervousParasympathetic nervous
systemsystem
increases cardiac outputincreases cardiac output decreases cardiac outputdecreases cardiac output
increases blood pressureincreases blood pressure decreases blood pressuredecreases blood pressure
dilates bronchiolesdilates bronchioles constrict bronchiolesconstrict bronchioles
increases ventilation rateincreases ventilation rate decreases ventilation ratedecreases ventilation rate
dilates pupilsdilates pupils constrict pupilconstrict pupil

26. Sympathetic nervous systemSympathetic nervous system Parasympathetic nervousParasympathetic nervous
systemsystem
contracts anal & bladdercontracts anal & bladder
sphincterssphincters
relaxes anal & bladderrelaxes anal & bladder
sphincterssphincters
increases sweat productionincreases sweat production no comparable effectno comparable effect
no comparable effectno comparable effect increases secretion of tearsincreases secretion of tears